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-.\"  OpenVPN -- An application to securely tunnel IP networks
-.\"             over a single TCP/UDP port, with support for SSL/TLS-based
-.\"             session authentication and key exchange,
-.\"             packet encryption, packet authentication, and
-.\"             packet compression.
-.\"
-.\"  Copyright (C) 2002-2010 OpenVPN Technologies, Inc. <sales@openvpn.net>
-.\"
-.\"  This program is free software; you can redistribute it and/or modify
-.\"  it under the terms of the GNU General Public License version 2
-.\"  as published by the Free Software Foundation.
-.\"
-.\"  This program is distributed in the hope that it will be useful,
-.\"  but WITHOUT ANY WARRANTY; without even the implied warranty of
-.\"  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-.\"  GNU General Public License for more details.
-.\"
-.\"  You should have received a copy of the GNU General Public License
-.\"  along with this program (see the file COPYING included with this
-.\"  distribution); if not, write to the Free Software Foundation, Inc.,
-.\"  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
-.\"
-.\" Manual page for openvpn
-.\
-.\" SH section heading
-.\" SS subsection heading
-.\" LP paragraph
-.\" IP indented paragraph
-.\" TP hanging label
-.\
-.\" .nf -- no formatting
-.\" .fi -- resume formatting
-.\" .ft 3 -- boldface
-.\" .ft -- normal face
-.\" .in +|-{n} -- indent
-.\"
-.TH openvpn 8 "17 November 2008"
-.\"*********************************************************
-.SH NAME
-openvpn \- secure IP tunnel daemon.
-.\"*********************************************************
-.SH SYNOPSIS
-.ft 3
-openvpn [ options ... ]
-.ft
-.\"*********************************************************
-.SH INTRODUCTION
-.LP
-OpenVPN is an open source VPN daemon by James Yonan.
-Because OpenVPN tries to
-be a universal VPN tool offering a great deal of flexibility,
-there are a lot of options on this manual page.
-If you're new to OpenVPN, you might want to skip ahead to the
-examples section where you will see how to construct simple
-VPNs on the command line without even needing a configuration file.
-
-Also note that there's more documentation and examples on
-the OpenVPN web site:
-.I http://openvpn.net/
-
-And if you would like to see a shorter version of this manual,
-see the openvpn usage message which can be obtained by
-running
-.B openvpn
-without any parameters.
-.\"*********************************************************
-.SH DESCRIPTION
-.LP
-OpenVPN is a robust and highly flexible VPN daemon.
-OpenVPN supports SSL/TLS security, ethernet bridging,
-TCP or UDP tunnel transport through proxies or NAT,
-support for dynamic IP addresses and DHCP,
-scalability to hundreds or thousands of users,
-and portability to most major OS platforms.
-
-OpenVPN is tightly bound to the OpenSSL library, and derives much
-of its crypto capabilities from it.
-
-OpenVPN supports
-conventional encryption
-using a pre-shared secret key
-.B (Static Key mode)
-or
-public key security
-.B (SSL/TLS mode)
-using client & server certificates.
-OpenVPN also
-supports non-encrypted TCP/UDP tunnels.  
-
-OpenVPN is designed to work with the
-.B TUN/TAP
-virtual networking interface that exists on most platforms.
-
-Overall, OpenVPN aims to offer many of the key features of IPSec but
-with a relatively lightweight footprint.
-.\"*********************************************************
-.SH OPTIONS
-OpenVPN allows any option to be placed either on the command line
-or in a configuration file.  Though all command line options are preceded
-by a double-leading-dash ("\-\-"), this prefix can be removed when
-an option is placed in a configuration file.
-.\"*********************************************************
-.TP
-.B \-\-help
-Show options.
-.\"*********************************************************
-.TP
-.B \-\-config file
-Load additional config options from
-.B file
-where each line corresponds to one command line option,
-but with the leading '\-\-' removed.
-
-If
-.B \-\-config file
-is the only option to the openvpn command,
-the
-.B \-\-config
-can be removed, and the command can be given as
-.B openvpn file
-
-Note that
-configuration files can be nested to a reasonable depth.
-
-Double quotation or single quotation characters ("", '')
-can be used to enclose single parameters containing whitespace,
-and "#" or ";" characters in the first column
-can be used to denote comments.
-
-Note that OpenVPN 2.0 and higher performs backslash-based shell
-escaping for characters not in single quotations,
-so the following mappings should be observed:
-
-.nf
-.ft 3
-.in +4
-\\\\       Maps to a single backslash character (\\).
-\\"       Pass a literal doublequote character ("), don't
-         interpret it as enclosing a parameter.
-\\[SPACE] Pass a literal space or tab character, don't
-         interpret it as a parameter delimiter.
-.in -4
-.ft
-.fi
-
-For example on Windows, use double backslashes to
-represent pathnames:
-
-.nf
-.ft 3
-.in +4
-secret "c:\\\\OpenVPN\\\\secret.key"
-.in -4
-.ft
-.fi
-
-For examples of configuration files,
-see
-.I http://openvpn.net/examples.html
-
-Here is an example configuration file:
-
-.nf
-.ft 3
-.in +4
-#
-# Sample OpenVPN configuration file for
-# using a pre-shared static key.
-#
-# '#' or ';' may be used to delimit comments.
-
-# Use a dynamic tun device.
-dev tun
-
-# Our remote peer
-remote mypeer.mydomain
-
-# 10.1.0.1 is our local VPN endpoint
-# 10.1.0.2 is our remote VPN endpoint
-ifconfig 10.1.0.1 10.1.0.2
-
-# Our pre-shared static key
-secret static.key
-.in -4
-.ft
-.fi
-.\"*********************************************************
-.SS Tunnel Options:
-.TP
-.B \-\-mode m
-Set OpenVPN major mode.  By default, OpenVPN runs in
-point-to-point mode ("p2p").  OpenVPN 2.0 introduces
-a new mode ("server") which implements a multi-client
-server capability.
-.\"*********************************************************
-.TP
-.B \-\-local host
-Local host name or IP address for bind.
-If specified, OpenVPN will bind to this address only.
-If unspecified, OpenVPN will bind to all interfaces.
-.\"*********************************************************
-.TP
-.B \-\-remote host [port] [proto]
-Remote host name or IP address.  On the client, multiple
-.B \-\-remote
-options may be specified for redundancy, each referring
-to a different OpenVPN server.  Specifying multiple
-.B \-\-remote
-options for this purpose is a special case of the more
-general connection-profile feature.  See the
-.B <connection>
-documentation below.
-
-The OpenVPN client will try to connect to a server at
-.B host:port
-in the order specified by the list of
-.B \-\-remote
-options.
-
-.B proto
-indicates the protocol to use when connecting with the
-remote, and may be "tcp" or "udp".
-
-The client will move on to the next host in the list,
-in the event of connection failure.
-Note that at any given time, the OpenVPN client
-will at most be connected to
-one server.
-
-Note that since UDP is connectionless, connection failure
-is defined by the
-.B \-\-ping
-and
-.B \-\-ping-restart
-options.
-
-Note the following corner case:  If you use multiple
-.B \-\-remote
-options, AND you are dropping root privileges on
-the client with
-.B \-\-user
-and/or
-.B \-\-group,
-AND the client is running a non-Windows OS, if the client needs
-to switch to a different server, and that server pushes
-back different TUN/TAP or route settings, the client may lack
-the necessary privileges to close and reopen the TUN/TAP interface.
-This could cause the client to exit with a fatal error.
-
-If
-.B \-\-remote
-is unspecified, OpenVPN will listen
-for packets from any IP address, but will not act on those packets unless
-they pass all authentication tests.  This requirement for authentication
-is binding on all potential peers, even those from known and supposedly
-trusted IP addresses (it is very easy to forge a source IP address on
-a UDP packet).
-
-When used in TCP mode, 
-.B \-\-remote
-will act as a filter, rejecting connections from any host which does
-not match
-.B host.
-
-If
-.B host
-is a DNS name which resolves to multiple IP addresses,
-one will be randomly
-chosen, providing a sort of basic load-balancing and
-failover capability.
-.\"*********************************************************
-.TP
-.B \-\-remote-random-hostname
-Add a random string (6 characters) to first DNS label of hostname to prevent
-DNS caching.  For example, "foo.bar.gov" would be modified to
-"<random-chars>.foo.bar.gov".
-.\"*********************************************************
-.TP
-.B <connection>
-Define a client connection
-profile.  Client connection profiles are groups of OpenVPN options that
-describe how to connect to a given OpenVPN server.  Client connection
-profiles are specified within an OpenVPN configuration file, and
-each profile is bracketed by
-.B <connection>
-and
-.B </connection>.
-
-An OpenVPN client will try each connection profile sequentially
-until it achieves a successful connection.  
-
-.B \-\-remote-random
-can be used to initially "scramble" the connection
-list.
-
-Here is an example of connection profile usage:
-
-.nf
-.ft 3
-.in +4
-client
-dev tun
-
-<connection>
-remote 198.19.34.56 1194 udp
-</connection>
-
-<connection>
-remote 198.19.34.56 443 tcp
-</connection>
-
-<connection>
-remote 198.19.34.56 443 tcp
-http-proxy 192.168.0.8 8080
-http-proxy-retry
-</connection>
-
-<connection>
-remote 198.19.36.99 443 tcp
-http-proxy 192.168.0.8 8080
-http-proxy-retry
-</connection>
-
-persist-key
-persist-tun
-pkcs12 client.p12
-ns-cert-type server
-verb 3
-.in -4
-.ft
-.fi
-
-First we try to connect to a server at 198.19.34.56:1194 using UDP.
-If that fails, we then try to connect to 198.19.34.56:443 using TCP.
-If that also fails, then try connecting through an HTTP proxy at 
-192.168.0.8:8080 to 198.19.34.56:443 using TCP.  Finally, try to
-connect through the same proxy to a server at 198.19.36.99:443
-using TCP.
-
-The following OpenVPN options may be used inside of
-a
-.B <connection>
-block:
-
-.B bind,
-.B connect-retry,
-.B connect-retry-max,
-.B connect-timeout,
-.B float,
-.B http-proxy,
-.B http-proxy-option,
-.B http-proxy-retry,
-.B http-proxy-timeout,
-.B local,
-.B lport,
-.B nobind,
-.B port,
-.B proto,
-.B remote,
-.B rport,
-.B socks-proxy, and
-.B socks-proxy-retry.
-
-A defaulting mechanism exists for specifying options to apply to
-all
-.B <connection>
-profiles.  If any of the above options (with the exception of
-.B remote
-) appear outside of a
-.B <connection>
-block, but in a configuration file which has one or more
-.B <connection>
-blocks, the option setting will be used as a default for
-.B <connection>
-blocks which follow it in the configuration file.
-
-For example, suppose the
-.B nobind
-option were placed in the sample configuration file above, near
-the top of the file, before the first
-.B <connection>
-block.  The effect would be as if
-.B nobind
-were declared in all
-.B <connection>
-blocks below it.
-.\"*********************************************************
-.TP
-.B \-\-proto-force p
-When iterating through connection profiles,
-only consider profiles using protocol
-.B p
-('tcp'|'udp'). 
-.\"*********************************************************
-.TP
-.B \-\-remote-random
-When multiple
-.B \-\-remote
-address/ports are specified, or if connection profiles are being
-used, initially randomize the order of the list
-as a kind of basic load-balancing measure.
-.\"*********************************************************
-.TP
-.B \-\-proto p
-Use protocol
-.B p
-for communicating with remote host.
-.B p
-can be
-.B udp,
-.B tcp-client,
-or
-.B tcp-server.
-
-The default protocol is
-.B udp
-when
-.B \-\-proto
-is not specified.
-
-For UDP operation,
-.B \-\-proto udp
-should be specified on both peers.
-
-For TCP operation, one peer must use
-.B \-\-proto tcp-server
-and the other must use
-.B \-\-proto tcp-client.
-A peer started with
-.B tcp-server
-will wait indefinitely for an incoming connection.  A peer
-started with
-.B tcp-client
-will attempt to connect, and if that fails, will sleep for 5
-seconds (adjustable via the
-.B \-\-connect-retry
-option) and try again infinite or up to N retries (adjustable via the
-.B \-\-connect-retry-max
-option).  Both TCP client and server will simulate
-a SIGUSR1 restart signal if either side resets the connection.
-
-OpenVPN is designed to operate optimally over UDP, but TCP capability is provided
-for situations where UDP cannot be used.
-In comparison with UDP, TCP will usually be
-somewhat less efficient and less robust when used over unreliable or congested
-networks.
-
-This article outlines some of problems with tunneling IP over TCP:
-
-.I http://sites.inka.de/sites/bigred/devel/tcp-tcp.html
-
-There are certain cases, however, where using TCP may be advantageous from
-a security and robustness perspective, such as tunneling non-IP or
-application-level UDP protocols, or tunneling protocols which don't
-possess a built-in reliability layer.
-.\"*********************************************************
-.TP
-.B \-\-connect-retry n
-For
-.B \-\-proto tcp-client,
-take
-.B n
-as the
-number of seconds to wait
-between connection retries (default=5).
-.\"*********************************************************
-.TP
-.B \-\-connect-timeout n
-For
-.B \-\-proto tcp-client,
-set connection timeout to
-.B n
-seconds (default=10).
-.\"*********************************************************
-.TP
-.B \-\-connect-retry-max n
-For
-.B \-\-proto tcp-client,
-take
-.B n
-as the
-number of retries of connection attempt (default=infinite).
-.\"*********************************************************
-.TP
-.B \-\-auto-proxy
-Try to sense HTTP or SOCKS proxy settings automatically.
-If no settings are present, a direct connection will be attempted.
-If both HTTP and SOCKS settings are present, HTTP will be preferred.
-If the HTTP proxy server requires a password, it will be queried from
-stdin or the management interface.  If the underlying OS doesn't support an API for
-returning proxy settings, a direct connection will be attempted.
-Currently, only Windows clients support this option via the
-InternetQueryOption API.
-This option exists in OpenVPN 2.1 or higher.
-.\"*********************************************************
-.TP
-.B \-\-show-proxy-settings
-Show sensed HTTP or SOCKS proxy settings. Currently, only Windows clients
-support this option.
-.\"*********************************************************
-.TP
-.B \-\-http-proxy server port [authfile|'auto'|'auto-nct'] [auth-method]
-Connect to remote host through an HTTP proxy at address
-.B server
-and port
-.B port.
-If HTTP Proxy-Authenticate is required,
-.B authfile
-is a file containing a username and password on 2 lines, or
-"stdin" to prompt from console.
-
-.B auth-method
-should be one of "none", "basic", or "ntlm".
-
-HTTP Digest authentication is supported as well, but only via
-the
-.B auto
-or
-.B auto-nct
-flags (below).
-
-The
-.B auto
-flag causes OpenVPN to automatically determine the
-.B auth-method
-and query stdin or the management interface for
-username/password credentials, if required.  This flag
-exists on OpenVPN 2.1 or higher.
-
-The
-.B auto-nct
-flag (no clear-text auth) instructs OpenVPN to automatically
-determine the authentication method, but to reject weak
-authentication protocols such as HTTP Basic Authentication.
-.\"*********************************************************
-.TP
-.B \-\-http-proxy-retry
-Retry indefinitely on HTTP proxy errors.  If an HTTP proxy error
-occurs, simulate a SIGUSR1 reset.
-.\"*********************************************************
-.TP
-.B \-\-http-proxy-timeout n
-Set proxy timeout to
-.B n
-seconds, default=5.
-.\"*********************************************************
-.TP
-.B \-\-http-proxy-option type [parm]
-Set extended HTTP proxy options.
-Repeat to set multiple options.
-
-.B VERSION version \-\-
-Set HTTP version number to
-.B version
-(default=1.0).
-
-.B AGENT user-agent \-\-
-Set HTTP "User-Agent" string to
-.B user-agent.
-.\"*********************************************************
-.TP
-.B \-\-socks-proxy server [port]
-Connect to remote host through a Socks5 proxy at address
-.B server
-and port
-.B port
-(default=1080).
-.\"*********************************************************
-.TP
-.B \-\-socks-proxy-retry
-Retry indefinitely on Socks proxy errors.  If a Socks proxy error
-occurs, simulate a SIGUSR1 reset.
-.\"*********************************************************
-.TP
-.B \-\-resolv-retry n
-If hostname resolve fails for
-.B \-\-remote,
-retry resolve for
-.B n
-seconds before failing.
-
-Set
-.B n
-to "infinite" to retry indefinitely.
-
-By default,
-.B \-\-resolv-retry infinite
-is enabled.  You can disable by setting n=0.
-.\"*********************************************************
-.TP
-.B \-\-float
-Allow remote peer to change its IP address and/or port number, such as due to
-DHCP (this is the default if
-.B \-\-remote
-is not used).
-.B \-\-float
-when specified with
-.B \-\-remote
-allows an OpenVPN session to initially connect to a peer
-at a known address, however if packets arrive from a new
-address and pass all authentication tests, the new address
-will take control of the session.  This is useful when
-you are connecting to a peer which holds a dynamic address
-such as a dial-in user or DHCP client.
-
-Essentially,
-.B \-\-float
-tells OpenVPN to accept authenticated packets
-from any address, not only the address which was specified in the
-.B \-\-remote
-option.
-.\"*********************************************************
-.TP
-.B \-\-ipchange cmd
-Execute shell command
-.B cmd
-when our remote ip-address is initially authenticated or
-changes.
-
-Execute as:
-
-.B cmd ip_address port_number
-
-Don't use
-.B \-\-ipchange
-in
-.B \-\-mode server
-mode.  Use a
-.B \-\-client-connect
-script instead.
-
-See the "Environmental Variables" section below for
-additional parameters passed as environmental variables.
-
-Note that
-.B cmd
-can be a shell command with multiple arguments, in which
-case all OpenVPN-generated arguments will be appended
-to
-.B cmd
-to build a command line which will be passed to the script.
-
-If you are running in a dynamic IP address environment where
-the IP addresses of either peer could change without notice,
-you can use this script, for example, to edit the
-.I /etc/hosts
-file with the current address of the peer.  The script will
-be run every time the remote peer changes its IP address.
-
-Similarly if
-.I our
-IP address changes due to DHCP, we should configure
-our IP address change script (see man page for
-.BR dhcpcd (8)
-) to deliver a
-.B SIGHUP
-or
-.B SIGUSR1
-signal to OpenVPN.  OpenVPN will then
-reestablish a connection with its most recently authenticated
-peer on its new IP address.
-.\"*********************************************************
-.TP
-.B \-\-port port
-TCP/UDP port number for both local and remote.  The current
-default of 1194 represents the official IANA port number
-assignment for OpenVPN and has been used since version 2.0-beta17.
-Previous versions used port 5000 as the default.
-.\"*********************************************************
-.TP
-.B \-\-lport port
-TCP/UDP port number for bind.
-.\"*********************************************************
-.TP
-.B \-\-rport port
-TCP/UDP port number for remote.
-.\"*********************************************************
-.TP
-.B \-\-bind
-Bind to local address and port. This is the default unless any of 
-.B \-\-proto tcp-client
-,
-.B \-\-http-proxy
-or
-.B \-\-socks-proxy
-are used.
-.\"*********************************************************
-.TP
-.B \-\-nobind
-Do not bind to local address and port.  The IP stack will allocate
-a dynamic port for returning packets.  Since the value of the dynamic port
-could not be known in advance by a peer, this option is only suitable for
-peers which will be initiating connections by using the
-.B \-\-remote
-option.
-.\"*********************************************************
-.TP
-.B \-\-dev tunX | tapX | null
-TUN/TAP virtual network device (
-.B X
-can be omitted for a dynamic device.)
-
-See examples section below
-for an example on setting up a TUN device.
-
-You must use either tun devices on both ends of the connection
-or tap devices on both ends.  You cannot mix them, as they
-represent different underlying network layers.
-
-.B tun
-devices encapsulate IPv4 or IPv6 (OSI Layer 3) while
-.B tap
-devices encapsulate Ethernet 802.3 (OSI Layer 2).
-.\"*********************************************************
-.TP
-.B \-\-dev-type device-type
-Which device type are we using?
-.B device-type
-should be
-.B tun
-(OSI Layer 3)
-or
-.B tap
-(OSI Layer 2).
-Use this option only if the TUN/TAP device used with
-.B \-\-dev
-does not begin with
-.B tun
-or
-.B tap.
-.\"*********************************************************
-.TP
-.B \-\-topology mode
-Configure virtual addressing topology when running in
-.B \-\-dev tun
-mode.  This directive has no meaning in
-.B \-\-dev tap
-mode, which always uses a
-.B subnet
-topology.
-
-If you set this directive on the server, the
-.B \-\-server
-and
-.B \-\-server-bridge
-directives will automatically push your chosen topology setting to clients
-as well.  This directive can also be manually pushed to clients.  Like the
-.B \-\-dev
-directive, this directive must always be compatible between client and server.
-
-.B mode
-can be one of:
-
-.B net30 \-\-
-Use a point-to-point topology, by allocating one /30 subnet per client.
-This is designed to allow point-to-point semantics when some
-or all of the connecting clients might be Windows systems.  This is the
-default on OpenVPN 2.0.
-
-.B p2p \-\-
-Use a point-to-point topology where the remote endpoint of the client's
-tun interface always points to the local endpoint of the server's tun interface.
-This mode allocates a single IP address per connecting client.
-Only use
-when none of the connecting clients are Windows systems.  This mode
-is functionally equivalent to the
-.B \-\-ifconfig-pool-linear
-directive which is available in OpenVPN 2.0 and is now deprecated.
-
-.B subnet \-\-
-Use a subnet rather than a point-to-point topology by
-configuring the tun interface with a local IP address and subnet mask,
-similar to the topology used in
-.B \-\-dev tap
-and ethernet bridging mode.
-This mode allocates a single IP address per connecting client and works on
-Windows as well.  Only available when server and clients are OpenVPN 2.1 or
-higher, or OpenVPN 2.0.x which has been manually patched with the
-.B \-\-topology
-directive code.  When used on Windows, requires version 8.2 or higher
-of the TAP-Win32 driver.  When used on *nix, requires that the tun
-driver supports an
-.BR ifconfig (8)
-command which sets a subnet instead of a remote endpoint IP address.
-
-This option exists in OpenVPN 2.1 or higher.
-.\"*********************************************************
-.TP
-.B \-\-tun-ipv6
-Build a tun link capable of forwarding IPv6 traffic.
-Should be used in conjunction with
-.B \-\-dev tun
-or
-.B \-\-dev tunX.
-A warning will be displayed
-if no specific IPv6 TUN support for your OS has been compiled into OpenVPN.
-.\"*********************************************************
-.TP
-.B \-\-dev-node node
-Explicitly set the device node rather than using
-/dev/net/tun, /dev/tun, /dev/tap, etc.  If OpenVPN
-cannot figure out whether
-.B node
-is a TUN or TAP device based on the name, you should
-also specify
-.B \-\-dev-type tun
-or
-.B \-\-dev-type tap.
-
-On Windows systems, select the TAP-Win32 adapter which
-is named
-.B node
-in the Network Connections Control Panel or the
-raw GUID of the adapter enclosed by braces.
-The
-.B \-\-show-adapters
-option under Windows can also be used
-to enumerate all available TAP-Win32
-adapters and will show both the network
-connections control panel name and the GUID for
-each TAP-Win32 adapter.
-.TP
-.B \-\-lladdr address
-Specify the link layer address, more commonly known as the MAC address.
-Only applied to TAP devices.
-.\"*********************************************************
-.TP
-.B \-\-iproute cmd
-Set alternate command to execute instead of default iproute2 command.
-May be used in order to execute OpenVPN in unprivileged environment.
-.\"*********************************************************
-.TP
-.B \-\-ifconfig l rn
-Set TUN/TAP adapter parameters. 
-.B l
-is the IP address of the local VPN endpoint.
-For TUN devices,
-.B rn
-is the IP address of the remote VPN endpoint.
-For TAP devices,
-.B rn
-is the subnet mask of the virtual ethernet segment
-which is being created or connected to.
-
-For TUN devices, which facilitate virtual
-point-to-point IP connections,
-the proper usage of
-.B \-\-ifconfig
-is to use two private IP addresses
-which are not a member of any
-existing subnet which is in use.
-The IP addresses may be consecutive
-and should have their order reversed
-on the remote peer.  After the VPN
-is established, by pinging
-.B rn,
-you will be pinging across the VPN.
-
-For TAP devices, which provide
-the ability to create virtual
-ethernet segments,
-.B \-\-ifconfig
-is used to set an IP address and
-subnet mask just as a physical
-ethernet adapter would be
-similarly configured.  If you are
-attempting to connect to a remote
-ethernet bridge, the IP address
-and subnet should be set to values
-which would be valid on the
-the bridged ethernet segment (note
-also that DHCP can be used for the
-same purpose).
-
-This option, while primarily a proxy for the
-.BR ifconfig (8)
-command, is designed to simplify TUN/TAP
-tunnel configuration by providing a
-standard interface to the different
-ifconfig implementations on different
-platforms.
-
-.B \-\-ifconfig
-parameters which are IP addresses can
-also be specified as a DNS or /etc/hosts
-file resolvable name.
-
-For TAP devices,
-.B \-\-ifconfig
-should not be used if the TAP interface will be
-getting an IP address lease from a DHCP
-server.
-.\"*********************************************************
-.TP
-.B \-\-ifconfig-noexec
-Don't actually execute ifconfig/netsh commands, instead
-pass
-.B \-\-ifconfig
-parameters to scripts using environmental variables.
-.\"*********************************************************
-.TP
-.B \-\-ifconfig-nowarn
-Don't output an options consistency check warning
-if the
-.B \-\-ifconfig
-option on this side of the
-connection doesn't match the remote side.  This is useful
-when you want to retain the overall benefits of the
-options consistency check (also see
-.B \-\-disable-occ
-option) while only disabling the ifconfig component of
-the check.
-
-For example,
-if you have a configuration where the local host uses
-.B \-\-ifconfig
-but the remote host does not, use
-.B \-\-ifconfig-nowarn
-on the local host.
-
-This option will also silence warnings about potential
-address conflicts which occasionally annoy more experienced
-users by triggering "false positive" warnings.
-.\"*********************************************************
-.TP
-.B \-\-route network/IP [netmask] [gateway] [metric]
-Add route to routing table after connection is established.
-Multiple routes can be specified.  Routes will be
-automatically torn down in reverse order prior to
-TUN/TAP device close.
-
-This option is intended as
-a convenience proxy for the
-.BR route (8)
-shell command,
-while at the same time providing portable semantics
-across OpenVPN's platform space.
-
-.B netmask
-default \-\- 255.255.255.255
-
-.B gateway
-default \-\- taken from
-.B \-\-route-gateway
-or the second parameter to
-.B \-\-ifconfig
-when
-.B \-\-dev tun
-is specified.
-
-.B metric
-default \-\- taken from
-.B \-\-route-metric
-otherwise 0.
-
-The default can be specified by leaving an option blank or setting
-it to "default".
-
-The
-.B network
-and
-.B gateway
-parameters can
-also be specified as a DNS or /etc/hosts
-file resolvable name, or as one of three special keywords:
-
-.B vpn_gateway
-\-\- The remote VPN endpoint address
-(derived either from
-.B \-\-route-gateway
-or the second parameter to
-.B \-\-ifconfig
-when
-.B \-\-dev tun
-is specified).
-
-.B net_gateway
-\-\- The pre-existing IP default gateway, read from the routing
-table (not supported on all OSes).
-
-.B remote_host
-\-\- The
-.B \-\-remote
-address if OpenVPN is being run in client mode, and is undefined in server mode.
-.\"*********************************************************
-.TP
-.B \-\-max-routes n
-Allow a maximum number of n
-.B \-\-route
-options to be specified, either in the local configuration file,
-or pulled from an OpenVPN server.  By default, n=100.
-.\"*********************************************************
-.TP
-.B \-\-route-gateway gw|'dhcp'
-Specify a default gateway
-.B gw
-for use with
-.B \-\-route.
-
-If
-.B dhcp
-is specified as the parameter,
-the gateway address will be extracted from a DHCP
-negotiation with the OpenVPN server-side LAN.
-.\"*********************************************************
-.TP
-.B \-\-route-metric m
-Specify a default metric
-.B m
-for use with
-.B \-\-route.
-.\"*********************************************************
-.TP
-.B \-\-route-delay [n] [w]
-Delay
-.B n
-seconds (default=0) after connection
-establishment, before adding routes. If
-.B n
-is 0, routes will be added immediately upon connection
-establishment.  If
-.B \-\-route-delay
-is omitted, routes will be added immediately after TUN/TAP device
-open and
-.B \-\-up
-script execution, before any
-.B \-\-user
-or 
-.B \-\-group
-privilege downgrade (or
-.B \-\-chroot
-execution.)
-
-This option is designed to be useful in scenarios where DHCP is
-used to set
-tap adapter addresses.  The delay will give the DHCP handshake
-time to complete before routes are added.
-
-On Windows,
-.B \-\-route-delay
-tries to be more intelligent by waiting
-.B w
-seconds (w=30 by default)
-for the TAP-Win32 adapter to come up before adding routes.
-.\"*********************************************************
-.TP
-.B \-\-route-up cmd
-Execute shell command
-.B cmd
-after routes are added, subject to
-.B \-\-route-delay.
-
-See the "Environmental Variables" section below for
-additional parameters passed as environmental variables.
-
-Note that
-.B cmd
-can be a shell command with multiple arguments.
-.\"*********************************************************
-.TP
-.B \-\-route-noexec
-Don't add or remove routes automatically.  Instead pass routes to
-.B \-\-route-up
-script using environmental variables.
-.\"*********************************************************
-.TP
-.B \-\-route-nopull
-When used with
-.B \-\-client
-or
-.B \-\-pull,
-accept options pushed by server EXCEPT for routes.
-
-When used on the client, this option effectively bars the
-server from adding routes to the client's routing table,
-however note that this option still allows the server
-to set the TCP/IP properties of the client's TUN/TAP interface.
-.\"*********************************************************
-.TP
-.B \-\-allow-pull-fqdn
-Allow client to pull DNS names from server (rather than being limited
-to IP address) for
-.B \-\-ifconfig,
-.B \-\-route,
-and
-.B \-\-route-gateway.
-.\"*********************************************************
-.TP
-.B \-\-redirect-gateway flags...
-(Experimental) Automatically execute routing commands to cause all outgoing IP traffic
-to be redirected over the VPN.
-
-This option performs three steps:
-
-.B (1)
-Create a static route for the
-.B \-\-remote
-address which forwards to the pre-existing default gateway.
-This is done so that
-.B (3)
-will not create a routing loop.
-
-.B (2)
-Delete the default gateway route.
-
-.B (3)
-Set the new default gateway to be the VPN endpoint address (derived either from
-.B \-\-route-gateway
-or the second parameter to
-.B \-\-ifconfig
-when
-.B \-\-dev tun
-is specified).
-
-When the tunnel is torn down, all of the above steps are reversed so
-that the original default route is restored.
-
-Option flags:
-
-.B local \-\-
-Add the
-.B local
-flag if both OpenVPN servers are directly connected via a common subnet,
-such as with wireless.  The
-.B local
-flag will cause step
-.B 1
-above to be omitted.
-
-.B def1 \-\-
-Use this flag to override
-the default gateway by using 0.0.0.0/1 and 128.0.0.0/1
-rather than 0.0.0.0/0.  This has the benefit of overriding
-but not wiping out the original default gateway. 
-
-.B bypass-dhcp \-\-
-Add a direct route to the DHCP server (if it is non-local) which
-bypasses the tunnel
-(Available on Windows clients, may not be available
-on non-Windows clients).
-
-.B bypass-dns \-\-
-Add a direct route to the DNS server(s) (if they are non-local) which
-bypasses the tunnel
-(Available on Windows clients, may not be available
-on non-Windows clients).
-
-Using the def1 flag is highly recommended.
-.\"*********************************************************
-.TP
-.B \-\-redirect-private [flags]
-Like \-\-redirect-gateway, but omit actually changing the default
-gateway.  Useful when pushing private subnets.
-.\"*********************************************************
-.TP
-.B \-\-link-mtu n
-Sets an upper bound on the size of UDP packets which are sent
-between OpenVPN peers.  It's best not to set this parameter unless
-you know what you're doing.
-.\"*********************************************************
-.TP
-.B \-\-tun-mtu n
-Take the TUN device MTU to be
-.B n
-and derive the link MTU
-from it (default=1500).  In most cases, you will probably want to
-leave this parameter set to its default value.
-
-The MTU (Maximum Transmission Units) is
-the maximum datagram size in bytes that can be sent unfragmented
-over a particular network path.  OpenVPN requires that packets
-on the control or data channels be sent unfragmented.
-
-MTU problems often manifest themselves as connections which
-hang during periods of active usage.
-
-It's best to use the
-.B \-\-fragment
-and/or
-.B \-\-mssfix
-options to deal with MTU sizing issues.
-.\"*********************************************************
-.TP
-.B \-\-tun-mtu-extra n
-Assume that the TUN/TAP device might return as many as
-.B n
-bytes more than the
-.B \-\-tun-mtu
-size on read.  This parameter defaults to 0, which is sufficient for
-most TUN devices.  TAP devices may introduce additional overhead in excess
-of the MTU size, and a setting of 32 is the default when TAP devices are used.
-This parameter only controls internal OpenVPN buffer sizing,
-so there is no transmission overhead associated with using a larger value.
-.\"*********************************************************
-.TP
-.B \-\-mtu-disc type
-Should we do Path MTU discovery on TCP/UDP channel?  Only supported on OSes such
-as Linux that supports the necessary system call to set.
-
-.B 'no'
-\-\- Never send DF (Don't Fragment) frames
-.br
-.B 'maybe'
-\-\- Use per-route hints
-.br
-.B 'yes'
-\-\- Always DF (Don't Fragment)
-.br
-.\"*********************************************************
-.TP
-.B \-\-mtu-test
-To empirically measure MTU on connection startup,
-add the
-.B \-\-mtu-test
-option to your configuration.
-OpenVPN will send ping packets of various sizes
-to the remote peer and measure the largest packets
-which were successfully received.  The
-.B \-\-mtu-test
-process normally takes about 3 minutes to complete.
-.\"*********************************************************
-.TP
-.B \-\-fragment max
-Enable internal datagram fragmentation so
-that no UDP datagrams are sent which
-are larger than
-.B max
-bytes.
-
-The
-.B max
-parameter is interpreted in the same way as the
-.B \-\-link-mtu
-parameter, i.e. the UDP packet size after encapsulation
-overhead has been added in, but not including
-the UDP header itself.
-
-The
-.B \-\-fragment
-option only makes sense when you are using the UDP protocol (
-.B \-\-proto udp
-).
-
-.B \-\-fragment
-adds 4 bytes of overhead per datagram.
-
-See the
-.B \-\-mssfix
-option below for an important related option to
-.B \-\-fragment.
-
-It should also be noted that this option is not meant to replace
-UDP fragmentation at the IP stack level.  It is only meant as a
-last resort when path MTU discovery is broken.  Using this option
-is less efficient than fixing path MTU discovery for your IP link and
-using native IP fragmentation instead.
-
-Having said that, there are circumstances where using OpenVPN's
-internal fragmentation capability may be your only option, such
-as tunneling a UDP multicast stream which requires fragmentation.
-.\"*********************************************************
-.TP
-.B \-\-mssfix max
-Announce to TCP sessions running over the tunnel that they should limit
-their send packet sizes such that after OpenVPN has encapsulated them,
-the resulting UDP packet size that OpenVPN sends to its peer will not
-exceed
-.B max
-bytes. The default value is
-.B 1450.
-
-The
-.B max
-parameter is interpreted in the same way as the
-.B \-\-link-mtu
-parameter, i.e. the UDP packet size after encapsulation
-overhead has been added in, but not including
-the UDP header itself.
-
-The
-.B \-\-mssfix
-option only makes sense when you are using the UDP protocol
-for OpenVPN peer-to-peer communication, i.e.
-.B \-\-proto udp.
-
-.B \-\-mssfix
-and
-.B \-\-fragment
-can be ideally used together, where
-.B \-\-mssfix
-will try to keep TCP from needing
-packet fragmentation in the first place,
-and if big packets come through anyhow
-(from protocols other than TCP),
-.B \-\-fragment
-will internally fragment them.
-
-Both
-.B \-\-fragment
-and
-.B \-\-mssfix
-are designed to work around cases where Path MTU discovery
-is broken on the network path between OpenVPN peers.
-
-The usual symptom of such a breakdown is an OpenVPN
-connection which successfully starts, but then stalls
-during active usage.
-
-If
-.B \-\-fragment
-and
-.B \-\-mssfix
-are used together,
-.B \-\-mssfix
-will take its default
-.B max
-parameter from the
-.B \-\-fragment max
-option.
-
-Therefore, one could lower the maximum UDP packet size
-to 1300 (a good first try for solving MTU-related
-connection problems) with the following options:
-
-.B \-\-tun-mtu 1500 \-\-fragment 1300 \-\-mssfix
-.\"*********************************************************
-.TP
-.B \-\-sndbuf size
-Set the TCP/UDP socket send buffer size.
-Currently defaults to 65536 bytes.
-.\"*********************************************************
-.TP
-.B \-\-rcvbuf size
-Set the TCP/UDP socket receive buffer size.
-Currently defaults to 65536 bytes.
-.\"*********************************************************
-.TP
-.B \-\-socket-flags flags...
-Apply the given flags to the OpenVPN transport socket.
-Currently, only
-.B TCP_NODELAY
-is supported.
-
-The
-.B TCP_NODELAY
-socket flag is useful in TCP mode, and causes the kernel
-to send tunnel packets immediately over the TCP connection without
-trying to group several smaller packets into a larger packet.
-This can result in a considerably improvement in latency.
-
-This option is pushable from server to client, and should be used
-on both client and server for maximum effect.
-.\"*********************************************************
-.TP
-.B \-\-txqueuelen n
-(Linux only) Set the TX queue length on the TUN/TAP interface.
-Currently defaults to 100.
-.\"*********************************************************
-.TP
-.B \-\-shaper n
-Limit bandwidth of outgoing tunnel data to
-.B n
-bytes per second on the TCP/UDP port.
-If you want to limit the bandwidth
-in both directions, use this option on both peers.
-
-OpenVPN uses the following algorithm to implement
-traffic shaping: Given a shaper rate of
-.I n
-bytes per second, after a datagram write of
-.I b
-bytes is queued on the TCP/UDP port, wait a minimum of
-.I (b / n)
-seconds before queuing the next write.
-
-It should be noted that OpenVPN supports multiple
-tunnels between the same two peers, allowing you
-to construct full-speed and reduced bandwidth tunnels
-at the same time,
-routing low-priority data such as off-site backups
-over the reduced bandwidth tunnel, and other data
-over the full-speed tunnel.
-
-Also note that for low bandwidth tunnels
-(under 1000 bytes per second), you should probably
-use lower MTU values as well (see above), otherwise
-the packet latency will grow so large as to trigger
-timeouts in the TLS layer and TCP connections running
-over the tunnel.
-
-OpenVPN allows
-.B n
-to be between 100 bytes/sec and 100 Mbytes/sec.
-.\"*********************************************************
-.TP
-.B \-\-inactive n [bytes]
-Causes OpenVPN to exit after
-.B n
-seconds of inactivity on the TUN/TAP device. The time length of
-inactivity is measured since the last incoming or outgoing tunnel
-packet.  The default value is 0 seconds, which disables this feature.
-
-If the optional
-.B bytes
-parameter is included,
-exit if less than
-.B bytes
-of combined in/out traffic are produced on the tun/tap device
-in
-.B n
-seconds.
-
-In any case, OpenVPN's internal ping packets (which are just
-keepalives) and TLS control packets are not considered
-"activity", nor are they counted as traffic, as they are used
-internally by OpenVPN and are not an indication of actual user
-activity.
-.\"*********************************************************
-.TP
-.B \-\-ping n
-Ping remote over the TCP/UDP control channel
-if no packets have been sent for at least
-.B n
-seconds (specify
-.B \-\-ping
-on both peers to cause ping packets to be sent in both directions since
-OpenVPN ping packets are not echoed like IP ping packets).
-When used in one of OpenVPN's secure modes (where
-.B \-\-secret, \-\-tls-server,
-or
-.B \-\-tls-client
-is specified), the ping packet
-will be cryptographically secure.
-
-This option has two intended uses:
-
-(1) Compatibility
-with stateful firewalls.  The periodic ping will ensure that
-a stateful firewall rule which allows OpenVPN UDP packets to
-pass will not time out.
-
-(2) To provide a basis for the remote to test the existence
-of its peer using the
-.B \-\-ping-exit
-option.
-.\"*********************************************************
-.TP
-.B \-\-ping-exit n
-Causes OpenVPN to exit after
-.B n
-seconds pass without reception of a ping
-or other packet from remote.
-This option can be combined with
-.B \-\-inactive, \-\-ping,
-and
-.B \-\-ping-exit
-to create a two-tiered inactivity disconnect.
-
-For example,
-
-.B openvpn [options...] \-\-inactive 3600 \-\-ping 10 \-\-ping-exit 60
-
-when used on both peers will cause OpenVPN to exit within 60
-seconds if its peer disconnects, but will exit after one
-hour if no actual tunnel data is exchanged.
-.\"*********************************************************
-.TP
-.B \-\-ping-restart n
-Similar to
-.B \-\-ping-exit,
-but trigger a
-.B SIGUSR1
-restart after
-.B n
-seconds pass without reception of a ping
-or other packet from remote.
-
-This option is useful in cases
-where the remote peer has a dynamic IP address and
-a low-TTL DNS name is used to track the IP address using
-a service such as
-.I http://dyndns.org/
-+ a dynamic DNS client such
-as
-.B ddclient.
-
-If the peer cannot be reached, a restart will be triggered, causing
-the hostname used with
-.B \-\-remote
-to be re-resolved (if
-.B \-\-resolv-retry
-is also specified).
-
-In server mode,
-.B \-\-ping-restart, \-\-inactive,
-or any other type of internally generated signal will always be
-applied to
-individual client instance objects, never to whole server itself.
-Note also in server mode that any internally generated signal
-which would normally cause a restart, will cause the deletion
-of the client instance object instead.
-
-In client mode, the
-.B \-\-ping-restart
-parameter is set to 120 seconds by default.  This default will
-hold until the client pulls a replacement value from the server, based on
-the
-.B \-\-keepalive
-setting in the server configuration.
-To disable the 120 second default, set
-.B \-\-ping-restart 0
-on the client.
-
-See the signals section below for more information
-on
-.B SIGUSR1.
-
-Note that the behavior of
-.B SIGUSR1
-can be modified by the
-.B \-\-persist-tun, \-\-persist-key, \-\-persist-local-ip,
-and
-.B \-\-persist-remote-ip
-options.
-
-Also note that
-.B \-\-ping-exit
-and
-.B \-\-ping-restart
-are mutually exclusive and cannot be used together.
-.\"*********************************************************
-.TP
-.B \-\-keepalive n m
-A helper directive designed to simplify the expression of
-.B \-\-ping
-and
-.B \-\-ping-restart
-in server mode configurations.
-
-For example,
-.B \-\-keepalive 10 60
-expands as follows:
-
-.nf
-.ft 3
-.in +4
- if mode server:
-   ping 10
-   ping-restart 120
-   push "ping 10"
-   push "ping-restart 60"
- else
-   ping 10
-   ping-restart 60
-.in -4
-.ft
-.fi
-.\"*********************************************************
-.TP
-.B \-\-ping-timer-rem
-Run the
-.B \-\-ping-exit
-/
-.B \-\-ping-restart
-timer only if we have a remote address.  Use this option if you are
-starting the daemon in listen mode (i.e. without an explicit
-.B \-\-remote
-peer), and you don't want to start clocking timeouts until a remote
-peer connects.
-.\"*********************************************************
-.TP
-.B \-\-persist-tun
-Don't close and reopen TUN/TAP device or run up/down scripts
-across
-.B SIGUSR1
-or
-.B \-\-ping-restart
-restarts.
-
-.B SIGUSR1
-is a restart signal similar to
-.B SIGHUP,
-but which offers finer-grained control over
-reset options.
-.\"*********************************************************
-.TP
-.B \-\-persist-key
-Don't re-read key files across
-.B SIGUSR1
-or
-.B \-\-ping-restart.
-
-This option can be combined with
-.B \-\-user nobody
-to allow restarts triggered by the
-.B SIGUSR1
-signal.
-Normally if you drop root privileges in OpenVPN,
-the daemon cannot be restarted since it will now be unable to re-read protected
-key files.
-
-This option solves the problem by persisting keys across
-.B SIGUSR1
-resets, so they don't need to be re-read.
-.\"*********************************************************
-.TP
-.B \-\-persist-local-ip
-Preserve initially resolved local IP address and port number
-across
-.B SIGUSR1
-or
-.B \-\-ping-restart
-restarts.
-.\"*********************************************************
-.TP
-.B \-\-persist-remote-ip
-Preserve most recently authenticated remote IP address and port number
-across
-.B SIGUSR1
-or
-.B \-\-ping-restart
-restarts.
-.\"*********************************************************
-.TP
-.B \-\-mlock
-Disable paging by calling the POSIX mlockall function.
-Requires that OpenVPN be initially run as root (though
-OpenVPN can subsequently downgrade its UID using the
-.B \-\-user
-option).
-
-Using this option ensures that key material and tunnel
-data are never written to disk due to virtual
-memory paging operations which occur under most
-modern operating systems.  It ensures that even if an
-attacker was able to crack the box running OpenVPN, he
-would not be able to scan the system swap file to
-recover previously used
-ephemeral keys, which are used for a period of time
-governed by the
-.B \-\-reneg
-options (see below), then are discarded.
-
-The downside
-of using
-.B \-\-mlock
-is that it will reduce the amount of physical
-memory available to other applications.
-.\"*********************************************************
-.TP
-.B \-\-up cmd
-Shell command to run after successful TUN/TAP device open
-(pre
-.B \-\-user
-UID change).  The up script is useful for specifying route
-commands which route IP traffic destined for
-private subnets which exist at the other
-end of the VPN connection into the tunnel.
-
-For
-.B \-\-dev tun
-execute as:
-
-.B cmd tun_dev tun_mtu link_mtu ifconfig_local_ip ifconfig_remote_ip [ init | restart ]
-
-For
-.B \-\-dev tap
-execute as:
-
-.B cmd tap_dev tap_mtu link_mtu ifconfig_local_ip ifconfig_netmask [ init | restart ]
-
-See the "Environmental Variables" section below for
-additional parameters passed as environmental variables.
-
-Note that
-.B cmd
-can be a shell command with multiple arguments, in which
-case all OpenVPN-generated arguments will be appended
-to
-.B cmd
-to build a command line which will be passed to the shell.
-
-Typically,
-.B cmd
-will run a script to add routes to the tunnel.
-
-Normally the up script is called after the TUN/TAP device is opened.
-In this context, the last command line parameter passed to the script
-will be
-.I init.
-If the
-.B \-\-up-restart
-option is also used, the up script will be called for restarts as
-well.  A restart is considered to be a partial reinitialization
-of OpenVPN where the TUN/TAP instance is preserved (the
-.B \-\-persist-tun
-option will enable such preservation).  A restart
-can be generated by a SIGUSR1 signal, a
-.B \-\-ping-restart
-timeout, or a connection reset when the TCP protocol is enabled
-with the
-.B \-\-proto
-option.  If a restart occurs, and
-.B \-\-up-restart
-has been specified, the up script will be called with
-.I restart
-as the last parameter.
-
-The following standalone example shows how the
-.B \-\-up
-script can be called in both an initialization and restart context.
-(NOTE: for security reasons, don't run the following example unless UDP port
-9999 is blocked by your firewall.  Also, the example will run indefinitely,
-so you should abort with control-c).
-
-.B openvpn \-\-dev tun \-\-port 9999 \-\-verb 4 \-\-ping-restart 10 \-\-up 'echo up' \-\-down 'echo down' \-\-persist-tun \-\-up-restart
-
-Note that OpenVPN also provides the
-.B \-\-ifconfig
-option to automatically ifconfig the TUN device,
-eliminating the need to define an
-.B \-\-up
-script, unless you also want to configure routes
-in the
-.B \-\-up
-script.
-
-If
-.B \-\-ifconfig
-is also specified, OpenVPN will pass the ifconfig local
-and remote endpoints on the command line to the
-.B \-\-up
-script so that they can be used to configure routes such as:
-
-.B route add -net 10.0.0.0 netmask 255.255.255.0 gw $5
-.\"*********************************************************
-.TP
-.B \-\-up-delay
-Delay TUN/TAP open and possible
-.B \-\-up
-script execution
-until after TCP/UDP connection establishment with peer.
-
-In
-.B \-\-proto udp
-mode, this option normally requires the use of
-.B \-\-ping
-to allow connection initiation to be sensed in the absence
-of tunnel data, since UDP is a "connectionless" protocol.
-
-On Windows, this option will delay the TAP-Win32 media state
-transitioning to "connected" until connection establishment,
-i.e. the receipt of the first authenticated packet from the peer.
-.\"*********************************************************
-.TP
-.B \-\-down cmd
-Shell command to run after TUN/TAP device close
-(post
-.B \-\-user
-UID change and/or
-.B \-\-chroot
-).  Called with the same parameters and environmental
-variables as the
-.B \-\-up
-option above.
-
-Note that if you reduce privileges by using
-.B \-\-user
-and/or
-.B \-\-group,
-your
-.B \-\-down
-script will also run at reduced privilege.
-.\"*********************************************************
-.TP
-.B \-\-down-pre
-Call
-.B \-\-down
-cmd/script before, rather than after, TUN/TAP close.
-.\"*********************************************************
-.TP
-.B \-\-up-restart
-Enable the
-.B \-\-up
-and
-.B \-\-down
-scripts to be called for restarts as well as initial program start.
-This option is described more fully above in the
-.B \-\-up
-option documentation.
-.\"*********************************************************
-.TP
-.B \-\-setenv name value
-Set a custom environmental variable
-.B name=value
-to pass to script.
-.\"*********************************************************
-.TP
-.B \-\-setenv FORWARD_COMPATIBLE 1
-Relax config file syntax checking so that unknown directives
-will trigger a warning but not a fatal error,
-on the assumption that a given unknown directive might be valid
-in future OpenVPN versions.
-
-This option should be used with caution, as there are good security
-reasons for having OpenVPN fail if it detects problems in a
-config file.  Having said that, there are valid reasons for wanting
-new software features to gracefully degrade when encountered by
-older software versions.
-.\"*********************************************************
-.TP
-.B \-\-setenv-safe name value
-Set a custom environmental variable
-.B OPENVPN_name=value
-to pass to script.
-
-This directive is designed to be pushed by the server to clients,
-and the prepending of "OPENVPN_" to the environmental variable
-is a safety precaution to prevent a LD_PRELOAD style attack
-from a malicious or compromised server.
-.\"*********************************************************
-.TP
-.B \-\-script-security level [method]
-This directive offers policy-level control over OpenVPN's usage of external programs
-and scripts.  Lower
-.B level
-values are more restrictive, higher values are more permissive.  Settings for
-.B level:
-
-.B 0 \-\-
-Strictly no calling of external programs.
-.br
-.B 1 \-\-
-(Default) Only call built-in executables such as ifconfig, ip, route, or netsh.
-.br
-.B 2 \-\-
-Allow calling of built-in executables and user-defined scripts.
-.br
-.B 3 \-\-
-Allow passwords to be passed to scripts via environmental variables (potentially unsafe).
-
-The
-.B method
-parameter indicates how OpenVPN should call external commands and scripts.
-Settings for
-.B method:
-
-.B execve \-\-
-(default) Use execve() function on Unix family OSes and CreateProcess() on Windows.
-.br
-.B system \-\-
-Use system() function (deprecated and less safe since the external program command
-line is subject to shell expansion).
-
-The
-.B \-\-script-security
-option was introduced in OpenVPN 2.1_rc9.  For configuration file compatibility
-with previous OpenVPN versions, use:
-.B \-\-script-security 3 system
-.\"*********************************************************
-.TP
-.B \-\-disable-occ
-Don't output a warning message if option inconsistencies are detected between
-peers.  An example of an option inconsistency would be where one peer uses
-.B \-\-dev tun
-while the other peer uses
-.B \-\-dev tap.
-
-Use of this option is discouraged, but is provided as
-a temporary fix in situations where a recent version of OpenVPN must
-connect to an old version.
-.\"*********************************************************
-.TP
-.B \-\-user user
-Change the user ID of the OpenVPN process to
-.B user
-after initialization, dropping privileges in the process.
-This option is useful to protect the system
-in the event that some hostile party was able to gain control of
-an OpenVPN session.  Though OpenVPN's security features make
-this unlikely, it is provided as a second line of defense.
-
-By setting
-.B user
-to
-.I nobody
-or somebody similarly unprivileged, the hostile party would be
-limited in what damage they could cause.  Of course once
-you take away privileges, you cannot return them
-to an OpenVPN session.  This means, for example, that if
-you want to reset an OpenVPN daemon with a
-.B SIGUSR1
-signal
-(for example in response
-to a DHCP reset), you should make use of one or more of the
-.B \-\-persist
-options to ensure that OpenVPN doesn't need to execute any privileged
-operations in order to restart (such as re-reading key files
-or running
-.BR ifconfig
-on the TUN device).
-.\"*********************************************************
-.TP
-.B \-\-group group
-Similar to the
-.B \-\-user
-option,
-this option changes the group ID of the OpenVPN process to
-.B group
-after initialization.
-.\"*********************************************************
-.TP
-.B \-\-cd dir
-Change directory to
-.B dir
-prior to reading any files such as
-configuration files, key files, scripts, etc.
-.B dir
-should be an absolute path, with a leading "/",
-and without any references
-to the current directory such as "." or "..".
-
-This option is useful when you are running
-OpenVPN in 
-.B \-\-daemon
-mode, and you want to consolidate all of
-your OpenVPN control files in one location.
-.\"*********************************************************
-.TP
-.B \-\-chroot dir
-Chroot to
-.B dir
-after initialization.  
-.B \-\-chroot
-essentially redefines
-.B dir
-as being the top
-level directory tree (/).  OpenVPN will therefore
-be unable to access any files outside this tree.
-This can be desirable from a security standpoint.
-
-Since the chroot operation is delayed until after
-initialization, most OpenVPN options that reference
-files will operate in a pre-chroot context.
-
-In many cases, the
-.B dir
-parameter can point to an empty directory, however
-complications can result when scripts or restarts
-are executed after the chroot operation.
-.\"*********************************************************
-.TP
-.B \-\-setcon context
-Apply SELinux
-.B context
-after initialization. This
-essentially provides the ability to restrict OpenVPN's
-rights to only network I/O operations, thanks to
-SELinux. This goes further than
-.B \-\-user
-and
-.B \-\-chroot
-in that those two, while being great security features,
-unfortunately do not protect against privilege escalation
-by exploitation of a vulnerable system call. You can of
-course combine all three, but please note that since
-setcon requires access to /proc you will have to provide
-it inside the chroot directory (e.g. with mount \-\-bind).
-
-Since the setcon operation is delayed until after
-initialization, OpenVPN can be restricted to just
-network-related system calls, whereas by applying the
-context before startup (such as the OpenVPN one provided
-in the SELinux Reference Policies) you will have to
-allow many things required only during initialization.
-
-Like with chroot, complications can result when scripts
-or restarts are executed after the setcon operation,
-which is why you should really consider using the
-.B \-\-persist-key
-and
-.B \-\-persist-tun
-options.
-.\"*********************************************************
-.TP
-.B \-\-daemon [progname]
-Become a daemon after all initialization functions are completed.
-This option will cause all message and error output to
-be sent to the syslog file (such as /var/log/messages),
-except for the output of shell scripts and
-ifconfig commands,
-which will go to /dev/null unless otherwise redirected.
-The syslog redirection occurs immediately at the point
-that
-.B \-\-daemon
-is parsed on the command line even though
-the daemonization point occurs later.  If one of the
-.B \-\-log
-options is present, it will supercede syslog
-redirection.
-
-The optional
-.B progname
-parameter will cause OpenVPN to report its program name
-to the system logger as
-.B progname.
-This can be useful in linking OpenVPN messages
-in the syslog file with specific tunnels.
-When unspecified,
-.B progname
-defaults to "openvpn".
-
-When OpenVPN is run with the
-.B \-\-daemon
-option, it will try to delay daemonization until the majority of initialization
-functions which are capable of generating fatal errors are complete.  This means
-that initialization scripts can test the return status of the
-openvpn command for a fairly reliable indication of whether the command
-has correctly initialized and entered the packet forwarding event loop.
-
-In OpenVPN, the vast majority of errors which occur after initialization are non-fatal.
-.\"*********************************************************
-.TP
-.B \-\-syslog [progname]
-Direct log output to system logger, but do not become a daemon.
-See
-.B \-\-daemon
-directive above for description of
-.B progname
-parameter.
-.\"*********************************************************
-.TP
-.B \-\-passtos
-Set the TOS field of the tunnel packet to what the payload's TOS is.
-.\"*********************************************************
-.TP
-.B \-\-inetd [wait|nowait] [progname]
-Use this option when OpenVPN is being run from the inetd or
-.BR xinetd(8)
-server.
-
-The
-.B wait/nowait
-option must match what is specified in the inetd/xinetd
-config file.  The
-.B nowait
-mode can only be used with
-.B \-\-proto tcp-server.
-The default is
-.B wait.
-The
-.B nowait
-mode can be used to instantiate the OpenVPN daemon as a classic TCP server,
-where client connection requests are serviced on a single
-port number.  For additional information on this kind of configuration,
-see the OpenVPN FAQ:
-.I http://openvpn.net/faq.html#oneport
-
-This option precludes the use of
-.B \-\-daemon, \-\-local,
-or
-.B \-\-remote.
-Note that this option causes message and error output to be handled in the same
-way as the
-.B \-\-daemon
-option.  The optional
-.B progname
-parameter is also handled exactly as in
-.B \-\-daemon.
-
-Also note that in
-.B wait
-mode, each OpenVPN tunnel requires a separate TCP/UDP port and
-a separate inetd or xinetd entry.  See the OpenVPN 1.x HOWTO for an example
-on using OpenVPN with xinetd:
-.I http://openvpn.net/1xhowto.html
-.\"*********************************************************
-.TP
-.B \-\-log file
-Output logging messages to
-.B file,
-including output to stdout/stderr which
-is generated by called scripts.
-If
-.B file
-already exists it will be truncated.
-This option takes effect
-immediately when it is parsed in the command line
-and will supercede syslog output if
-.B \-\-daemon
-or
-.B \-\-inetd
-is also specified.
-This option is persistent over the entire course of
-an OpenVPN instantiation and will not be reset by SIGHUP,
-SIGUSR1, or
-.B \-\-ping-restart.
-
-Note that on Windows, when OpenVPN is started as a service,
-logging occurs by default without the need to specify
-this option.
-.\"*********************************************************
-.TP
-.B \-\-log-append file
-Append logging messages to
-.B file.
-If
-.B file
-does not exist, it will be created.
-This option behaves exactly like
-.B \-\-log
-except that it appends to rather
-than truncating the log file.
-.\"*********************************************************
-.TP
-.B \-\-suppress-timestamps
-Avoid writing timestamps to log messages, even when they
-otherwise would be prepended. In particular, this applies to
-log messages sent to stdout.
-.\"*********************************************************
-.TP
-.B \-\-writepid file
-Write OpenVPN's main process ID to
-.B file.
-.\"*********************************************************
-.TP
-.B \-\-nice n
-Change process priority after initialization
-(
-.B n
-greater than 0 is lower priority,
-.B n
-less than zero is higher priority).
-.\"*********************************************************
-.\".TP
-.\".B \-\-nice-work n
-.\"Change priority of background TLS work thread.  The TLS thread
-.\"feature is enabled when OpenVPN is built
-.\"with pthread support, and you are running OpenVPN
-.\"in TLS mode (i.e. with
-.\".B \-\-tls-client
-.\"or
-.\".B \-\-tls-server
-.\"specified).
-.\"
-.\"Using a TLS thread offloads the CPU-intensive process of SSL/TLS-based
-.\"key exchange to a background thread so that it does not become
-.\"a latency bottleneck in the tunnel packet forwarding process.
-.\"
-.\"The parameter
-.\".B n
-.\"is interpreted exactly as with the
-.\".B \-\-nice
-.\"option above, but in relation to the work thread rather
-.\"than the main thread.
-.\"*********************************************************
-.TP
-.B \-\-fast-io
-(Experimental) Optimize TUN/TAP/UDP I/O writes by avoiding
-a call to poll/epoll/select prior to the write operation.  The purpose
-of such a call would normally be to block until the device
-or socket is ready to accept the write.  Such blocking is unnecessary
-on some platforms which don't support write blocking on UDP sockets
-or TUN/TAP devices.  In such cases, one can optimize the event loop
-by avoiding the poll/epoll/select call, improving CPU efficiency
-by 5% to 10%.
-
-This option can only be used on non-Windows systems, when
-.B \-\-proto udp
-is specified, and when
-.B \-\-shaper
-is NOT specified.
-.\"*********************************************************
-.TP
-.B \-\-multihome
-Configure a multi-homed UDP server.  This option can be used when
-OpenVPN has been configured to listen on all interfaces, and will
-attempt to bind client sessions to the interface on which packets
-are being received, so that outgoing packets will be sent out
-of the same interface.  Note that this option is only relevant for
-UDP servers and currently is only implemented on Linux.
-
-Note: clients connecting to a
-.B \-\-multihome
-server should always use the
-.B \-\-nobind
-option.
-.\"*********************************************************
-.TP
-.B \-\-echo [parms...]
-Echo
-.B parms
-to log output.
-
-Designed to be used to send messages to a controlling application
-which is receiving the OpenVPN log output.
-.\"*********************************************************
-.TP
-.B \-\-remap-usr1 signal
-Control whether internally or externally
-generated SIGUSR1 signals are remapped to
-SIGHUP (restart without persisting state) or
-SIGTERM (exit).
-
-.B signal
-can be set to "SIGHUP" or "SIGTERM".  By default, no remapping
-occurs.
-.\"*********************************************************
-.TP
-.B \-\-verb n
-Set output verbosity to
-.B n
-(default=1).  Each level shows all info from the previous levels.
-Level 3 is recommended if you want a good summary
-of what's happening without being swamped by output.
-
-.B 0 \-\-
-No output except fatal errors.
-.br
-.B 1 to 4 \-\-
-Normal usage range.
-.br
-.B 5 \-\-
-Output
-.B R
-and
-.B W
-characters to the console for each packet read and write, uppercase is
-used for TCP/UDP packets and lowercase is used for TUN/TAP packets.
-.br
-.B 6 to 11 \-\-
-Debug info range (see errlevel.h for additional
-information on debug levels).
-.\"*********************************************************
-.TP
-.B \-\-status file [n]
-Write operational status to
-.B file
-every
-.B n
-seconds.
-
-Status can also be written to the syslog by sending a
-.B SIGUSR2
-signal.
-.\"*********************************************************
-.TP
-.B \-\-status-version [n]
-Choose the status file format version number.  Currently
-.B n
-can be 1, 2, or 3 and defaults to 1.
-.\"*********************************************************
-.TP
-.B \-\-mute n
-Log at most
-.B n
-consecutive messages in the same category.  This is useful to
-limit repetitive logging of similar message types.
-.\"*********************************************************
-.TP
-.B \-\-comp-lzo [mode]
-Use fast LZO compression \-\- may add up to 1 byte per
-packet for incompressible data.
-.B mode
-may be "yes", "no", or "adaptive" (default).
-
-In a server mode setup, it is possible to selectively turn
-compression on or off for individual clients.
-
-First, make sure the client-side config file enables selective
-compression by having at least one
-.B \-\-comp-lzo
-directive, such as
-.B \-\-comp-lzo no.
-This will turn off compression by default,
-but allow a future directive push from the server to
-dynamically change the
-on/off/adaptive setting.
-
-Next in a
-.B \-\-client-config-dir
-file, specify the compression setting for the client,
-for example:
-
-.nf
-.ft 3
-.in +4
-comp-lzo yes
-push "comp-lzo yes"
-.in -4
-.ft
-.fi
-
-The first line sets the
-.B comp-lzo
-setting for the server
-side of the link, the second sets the client side.
-.\"*********************************************************
-.TP
-.B \-\-comp-noadapt
-When used in conjunction with
-.B \-\-comp-lzo,
-this option will disable OpenVPN's adaptive compression algorithm.
-Normally, adaptive compression is enabled with
-.B \-\-comp-lzo.
-
-Adaptive compression tries to optimize the case where you have
-compression enabled, but you are sending predominantly uncompressible
-(or pre-compressed) packets over the tunnel, such as an FTP or rsync transfer
-of a large, compressed file.  With adaptive compression,
-OpenVPN will periodically sample the compression process to measure its
-efficiency.  If the data being sent over the tunnel is already compressed,
-the compression efficiency will be very low, triggering openvpn to disable
-compression for a period of time until the next re-sample test.
-.\"*********************************************************
-.TP
-.B \-\-management IP port [pw-file]
-Enable a TCP server on
-.B IP:port
-to handle daemon management functions.
-.B pw-file,
-if specified,
-is a password file (password on first line)
-or "stdin" to prompt from standard input.  The password
-provided will set the password which TCP clients will need
-to provide in order to access management functions.
-
-The management interface can also listen on a unix domain socket,
-for those platforms that support it.  To use a unix domain socket, specify
-the unix socket pathname in place of
-.B IP
-and set
-.B port
-to 'unix'.  While the default behavior is to create a unix domain socket
-that may be connected to by any process, the
-.B \-\-management-client-user
-and
-.B \-\-management-client-group
-directives can be used to restrict access.
-
-The management interface provides a special mode where the TCP
-management link can operate over the tunnel itself.  To enable this mode,
-set
-.B IP
-= "tunnel".  Tunnel mode will cause the management interface
-to listen for a TCP connection on the local VPN address of the
-TUN/TAP interface.
-
-While the management port is designed for programmatic control
-of OpenVPN by other applications, it is possible to telnet
-to the port, using a telnet client in "raw" mode.  Once connected,
-type "help" for a list of commands.
-
-For detailed documentation on the management interface, see
-the management-notes.txt file in the
-.B management
-folder of
-the OpenVPN source distribution.
-
-It is strongly recommended that
-.B IP
-be set to 127.0.0.1
-(localhost) to restrict accessibility of the management
-server to local clients. 
-.TP
-.B \-\-management-client
-Management interface will connect as a TCP client to
-.B IP:port
-specified by
-.B \-\-management
-rather than listen as a TCP server.
-.\"*********************************************************
-.TP
-.B \-\-management-query-passwords
-Query management channel for private key password and
-.B \-\-auth-user-pass
-username/password.  Only query the management channel
-for inputs which ordinarily would have been queried from the
-console.
-.\"*********************************************************
-.TP
-.B \-\-management-forget-disconnect
-Make OpenVPN forget passwords when management session
-disconnects.
-
-This directive does not affect the
-.B \-\-http-proxy
-username/password.  It is always cached.
-.\"*********************************************************
-.TP
-.B \-\-management-hold
-Start OpenVPN in a hibernating state, until a client
-of the management interface explicitly starts it
-with the
-.B hold release
-command.
-.\"*********************************************************
-.TP
-.B \-\-management-signal
-Send SIGUSR1 signal to OpenVPN if management session disconnects.
-This is useful when you wish to disconnect an OpenVPN session on
-user logoff.
-.\"*********************************************************
-.TP
-.B \-\-management-log-cache n
-Cache the most recent
-.B n
-lines of log file history for usage
-by the management channel.
-.\"*********************************************************
-.TP
-.B \-\-management-client-auth
-Gives management interface client the responsibility
-to authenticate clients after their client certificate
-has been verified.  See management-notes.txt in OpenVPN
-distribution for detailed notes.
-.\"*********************************************************
-.TP
-.B \-\-management-client-pf
-Management interface clients must specify a packet
-filter file for each connecting client.  See management-notes.txt
-in OpenVPN distribution for detailed notes.
-.\"*********************************************************
-.TP
-.B \-\-management-client-user u
-When the management interface is listening on a unix domain socket,
-only allow connections from user
-.B u.
-.\"*********************************************************
-.TP
-.B \-\-management-client-group g
-When the management interface is listening on a unix domain socket,
-only allow connections from group
-.B g.
-.\"*********************************************************
-.TP
-.B \-\-plugin module-pathname [init-string]
-Load plug-in module from the file
-.B module-pathname,
-passing
-.B init-string
-as an argument
-to the module initialization function.  Multiple
-plugin modules may be loaded into one OpenVPN
-process.
-
-For more information and examples on how to build OpenVPN
-plug-in modules, see the README file in the
-.B plugin
-folder of the OpenVPN source distribution.
-
-If you are using an RPM install of OpenVPN, see
-/usr/share/openvpn/plugin.  The documentation is
-in
-.B doc
-and the actual plugin modules are in
-.B lib.
-
-Multiple plugin modules can be cascaded, and modules can be
-used in tandem with scripts.  The modules will be called by
-OpenVPN in the order that they are declared in the config
-file.  If both a plugin and script are configured for the same
-callback, the script will be called last.  If the
-return code of the module/script controls an authentication
-function (such as tls-verify, auth-user-pass-verify, or
-client-connect), then
-every module and script must return success (0) in order for
-the connection to be authenticated.
-.\"*********************************************************
-.SS Server Mode
-Starting with OpenVPN 2.0, a multi-client TCP/UDP server mode
-is supported, and can be enabled with the
-.B \-\-mode server
-option.  In server mode, OpenVPN will listen on a single
-port for incoming client connections.  All client
-connections will be routed through a single tun or tap
-interface.  This mode is designed for scalability and should
-be able to support hundreds or even thousands of clients
-on sufficiently fast hardware.  SSL/TLS authentication must
-be used in this mode.
-.\"*********************************************************
-.TP
-.B \-\-server network netmask
-A helper directive designed to simplify the configuration
-of OpenVPN's server mode.  This directive will set up an
-OpenVPN server which will allocate addresses to clients
-out of the given network/netmask.  The server itself
-will take the ".1" address of the given network
-for use as the server-side endpoint of the local
-TUN/TAP interface.
-
-For example,
-.B \-\-server 10.8.0.0 255.255.255.0
-expands as follows:
-
-.nf
-.ft 3
-.in +4
- mode server
- tls-server
- push "topology [topology]"
-
- if dev tun AND (topology == net30 OR topology == p2p):
-   ifconfig 10.8.0.1 10.8.0.2
-   if !nopool:
-     ifconfig-pool 10.8.0.4 10.8.0.251
-   route 10.8.0.0 255.255.255.0
-   if client-to-client:
-     push "route 10.8.0.0 255.255.255.0"
-   else if topology == net30:
-     push "route 10.8.0.1"
-
- if dev tap OR (dev tun AND topology == subnet):
-   ifconfig 10.8.0.1 255.255.255.0
-   if !nopool:
-     ifconfig-pool 10.8.0.2 10.8.0.254 255.255.255.0
-   push "route-gateway 10.8.0.1"
-.in -4
-.ft
-.fi
-
-Don't use
-.B \-\-server
-if you are ethernet bridging.  Use
-.B \-\-server-bridge
-instead.
-.\"*********************************************************
-.TP
-.B \-\-server-bridge gateway netmask pool-start-IP pool-end-IP
-.TP
-.B \-\-server-bridge ['nogw']
-
-A helper directive similar to
-.B \-\-server
-which is designed to simplify the configuration
-of OpenVPN's server mode in ethernet bridging configurations.
-
-If
-.B \-\-server-bridge
-is used without any parameters, it will enable a DHCP-proxy
-mode, where connecting OpenVPN clients will receive an IP
-address for their TAP adapter from the DHCP server running
-on the OpenVPN server-side LAN.
-Note that only clients that support
-the binding of a DHCP client with the TAP adapter (such as
-Windows) can support this mode.  The optional 
-.B nogw
-flag (advanced) indicates that gateway information should not be
-pushed to the client.
-
-To configure ethernet bridging, you 
-must first use your OS's bridging capability
-to bridge the TAP interface with the ethernet
-NIC interface.  For example, on Linux this is done
-with the
-.B brctl
-tool, and with Windows XP it is done in the Network
-Connections Panel by selecting the ethernet and
-TAP adapters and right-clicking on "Bridge Connections".
-
-Next you you must manually set the
-IP/netmask on the bridge interface.  The
-.B gateway
-and
-.B netmask
-parameters to
-.B \-\-server-bridge
-can be set to either the IP/netmask of the
-bridge interface, or the IP/netmask of the
-default gateway/router on the bridged
-subnet.
-
-Finally, set aside a IP range in the bridged
-subnet,
-denoted by
-.B pool-start-IP
-and
-.B pool-end-IP,
-for OpenVPN to allocate to connecting
-clients.
-
-For example,
-.B server-bridge 10.8.0.4 255.255.255.0 10.8.0.128 10.8.0.254
-expands as follows:
-
-.nf
-.ft 3
-.in +4
-mode server
-tls-server
-
-ifconfig-pool 10.8.0.128 10.8.0.254 255.255.255.0
-push "route-gateway 10.8.0.4"
-.in -4
-.ft
-.fi
-
-In another example,
-.B \-\-server-bridge
-(without parameters) expands as follows:
-
-.nf
-.ft 3
-.in +4
-mode server
-tls-server
-
-push "route-gateway dhcp"
-.in -4
-.ft
-.fi
-
-Or
-.B \-\-server-bridge nogw
-expands as follows:
-
-.nf
-.ft 3
-.in +4
-mode server
-tls-server
-.in -4
-.ft
-.fi
-.\"*********************************************************
-.TP
-.B \-\-push "option"
-Push a config file option back to the client for remote
-execution.  Note that
-.B
-option
-must be enclosed in double quotes ("").  The client must specify
-.B \-\-pull
-in its config file.  The set of options which can be
-pushed is limited by both feasibility and security.
-Some options such as those which would execute scripts
-are banned, since they would effectively allow a compromised
-server to execute arbitrary code on the client.
-Other options such as TLS or MTU parameters
-cannot be pushed because the client needs to know
-them before the connection to the server can be initiated.
-
-This is a partial list of options which can currently be pushed:
-.B \-\-route, \-\-route-gateway, \-\-route-delay, \-\-redirect-gateway,
-.B \-\-ip-win32, \-\-dhcp-option,
-.B \-\-inactive, \-\-ping, \-\-ping-exit, \-\-ping-restart,
-.B \-\-setenv,
-.B \-\-persist-key, \-\-persist-tun, \-\-echo,
-.B \-\-comp-lzo,
-.B \-\-socket-flags,
-.B \-\-sndbuf, \-\-rcvbuf
-.\"*********************************************************
-.TP
-.B \-\-push-reset
-Don't inherit the global push list for a specific client instance.
-Specify this option in a client-specific context such
-as with a
-.B \-\-client-config-dir
-configuration file.  This option will ignore
-.B \-\-push
-options at the global config file level.
-.\"*********************************************************
-.TP
-.B \-\-disable
-Disable a particular client (based on the common name)
-from connecting.  Don't use this option to disable a client
-due to key or password compromise.  Use a CRL (certificate
-revocation list) instead (see the
-.B \-\-crl-verify
-option).
-
-This option must be associated with a specific client instance,
-which means that it must be specified either in a client
-instance config file using
-.B \-\-client-config-dir
-or dynamically generated using a
-.B \-\-client-connect
-script.
-.\"*********************************************************
-.TP
-.B \-\-ifconfig-pool start-IP end-IP [netmask]
-Set aside a pool of subnets to be
-dynamically allocated to connecting clients, similar
-to a DHCP server.  For tun-style
-tunnels, each client will be given a /30 subnet (for
-interoperability with Windows clients).  For tap-style
-tunnels, individual addresses will be allocated, and the
-optional
-.B netmask
-parameter will also be pushed to clients.
-
-.\"*********************************************************
-.TP
-.B \-\-ifconfig-pool-persist file [seconds]
-Persist/unpersist ifconfig-pool
-data to
-.B file,
-at
-.B seconds
-intervals (default=600), as well as on program startup and
-shutdown.
-
-The goal of this option is to provide a long-term association
-between clients (denoted by their common name) and the virtual
-IP address assigned to them from the ifconfig-pool.
-Maintaining a long-term
-association is good for clients because it allows them
-to effectively use the
-.B \-\-persist-tun
-option.
-
-.B file
-is a comma-delimited ASCII file, formatted as
-<Common-Name>,<IP-address>.
-
-If
-.B seconds
-= 0,
-.B file
-will be treated as read-only.  This is useful if
-you would like to treat
-.B file
-as a configuration file.
-
-Note that the entries in this file are treated by OpenVPN as
-suggestions only, based on past associations between
-a common name and IP address.  They do not guarantee that the given common
-name will always receive the given IP address.  If you want guaranteed
-assignment, use
-.B \-\-ifconfig-push
-.\"*********************************************************
-.TP
-.B \-\-ifconfig-pool-linear
-Modifies the
-.B \-\-ifconfig-pool
-directive to
-allocate individual TUN interface addresses for
-clients rather than /30 subnets.  NOTE:  This option
-is incompatible with Windows clients.
-
-This option is deprecated, and should be replaced with
-.B \-\-topology p2p
-which is functionally equivalent.
-.\"*********************************************************
-.TP
-.B \-\-ifconfig-push local remote-netmask
-Push virtual IP endpoints for client tunnel,
-overriding the \-\-ifconfig-pool dynamic allocation.
-
-The parameters
-.B local
-and
-.B remote-netmask
-are set according to the
-.B \-\-ifconfig
-directive which you want to execute on the client machine to
-configure the remote end of the tunnel.  Note that the parameters
-.B local
-and
-.B remote-netmask
-are from the perspective of the client, not the server.  They may be
-DNS names rather than IP addresses, in which case they will be resolved
-on the server at the time of client connection.
-
-This option must be associated with a specific client instance,
-which means that it must be specified either in a client
-instance config file using
-.B \-\-client-config-dir
-or dynamically generated using a
-.B \-\-client-connect
-script.
-
-Remember also to include a
-.B \-\-route
-directive in the main OpenVPN config file which encloses
-.B local,
-so that the kernel will know to route it
-to the server's TUN/TAP interface.
-
-OpenVPN's internal client IP address selection algorithm works as
-follows:
-
-.B 1
-\-\- Use
-.B \-\-client-connect script
-generated file for static IP (first choice).
-.br
-.B 2
-\-\- Use
-.B \-\-client-config-dir
-file for static IP (next choice).
-.br
-.B 3
-\-\- Use
-.B \-\-ifconfig-pool
-allocation for dynamic IP (last choice).
-.br
-.\"*********************************************************
-.TP
-.B \-\-iroute network [netmask]
-Generate an internal route to a specific
-client. The
-.B netmask
-parameter, if omitted, defaults to 255.255.255.255.
-
-This directive can be used to route a fixed subnet from
-the server to a particular client, regardless
-of where the client is connecting from.  Remember
-that you must also add the route to the system
-routing table as well (such as by using the
-.B \-\-route
-directive).  The reason why two routes are needed
-is that the
-.B \-\-route
-directive routes the packet from the kernel
-to OpenVPN.  Once in OpenVPN, the
-.B \-\-iroute
-directive routes to the specific client.
-
-This option must be specified either in a client
-instance config file using
-.B \-\-client-config-dir
-or dynamically generated using a
-.B \-\-client-connect
-script.
-
-The
-.B \-\-iroute
-directive also has an important interaction with
-.B \-\-push
-"route ...".
-.B \-\-iroute
-essentially defines a subnet which is owned by a
-particular client (we will call this client A).
-If you would like other clients to be able to reach A's
-subnet, you can use
-.B \-\-push
-"route ..."
-together with
-.B \-\-client-to-client
-to effect this.  In order for all clients to see
-A's subnet, OpenVPN must push this route to all clients
-EXCEPT for A, since the subnet is already owned by A.
-OpenVPN accomplishes this by not
-not pushing a route to a client
-if it matches one of the client's iroutes.
-.\"*********************************************************
-.TP
-.B \-\-client-to-client
-Because the OpenVPN server mode handles multiple clients
-through a single tun or tap interface, it is effectively
-a router.  The
-.B \-\-client-to-client
-flag tells OpenVPN to internally route client-to-client
-traffic rather than pushing all client-originating traffic
-to the TUN/TAP interface.
-
-When this option is used, each client will "see" the other
-clients which are currently connected.  Otherwise, each
-client will only see the server.  Don't use this option
-if you want to firewall tunnel traffic using
-custom, per-client rules.
-.\"*********************************************************
-.TP
-.B \-\-duplicate-cn
-Allow multiple clients with the same common name to concurrently connect.
-In the absence of this option, OpenVPN will disconnect a client instance
-upon connection of a new client having the same common name.
-.\"*********************************************************
-.TP
-.B \-\-client-connect script
-Run
-.B script
-on client connection.  The script is passed the common name
-and IP address of the just-authenticated client
-as environmental variables (see environmental variable section
-below).  The script is also passed
-the pathname of a freshly created temporary file as $1
-(i.e. the first command line argument), to be used by the script
-to pass dynamically generated config file directives back to OpenVPN.
-
-If the script wants to generate a dynamic config file
-to be applied on the server when the client connects,
-it should write it to the file named by $1.
-
-See the
-.B \-\-client-config-dir
-option below for options which
-can be legally used in a dynamically generated config file.
-
-Note that the return value of
-.B script
-is significant.  If
-.B script
-returns a non-zero error status, it will cause the client
-to be disconnected.
-.\"*********************************************************
-.TP
-.B \-\-client-disconnect
-Like
-.B \-\-client-connect
-but called on client instance shutdown.  Will not be called
-unless the
-.B \-\-client-connect
-script and plugins (if defined)
-were previously called on this instance with
-successful (0) status returns.
-
-The exception to this rule is if the
-.B \-\-client-disconnect
-script or plugins are cascaded, and at least one client-connect
-function succeeded, then ALL of the client-disconnect functions for
-scripts and plugins will be called on client instance object deletion,
-even in cases where some of the related client-connect functions returned
-an error status.
-.B 
-.\"*********************************************************
-.TP
-.B \-\-client-config-dir dir
-Specify a directory
-.B dir
-for custom client config files.  After
-a connecting client has been authenticated, OpenVPN will
-look in this directory for a file having the same name
-as the client's X509 common name.  If a matching file
-exists, it will be opened and parsed for client-specific
-configuration options.  If no matching file is found, OpenVPN
-will instead try to open and parse a default file called
-"DEFAULT", which may be provided but is not required. Note that
-the configuration files must be readable by the OpenVPN process
-after it has dropped it's root privileges.
-
-This file can specify a fixed IP address for a given
-client using
-.B \-\-ifconfig-push,
-as well as fixed subnets owned by the client using
-.B \-\-iroute.
-
-One of the useful properties of this option is that it
-allows client configuration files to be conveniently
-created, edited, or removed while the server is live,
-without needing to restart the server.
-
-The following
-options are legal in a client-specific context:
-.B \-\-push, \-\-push-reset, \-\-iroute, \-\-ifconfig-push,
-and
-.B \-\-config.
-.\"*********************************************************
-.TP
-.B \-\-ccd-exclusive
-Require, as a
-condition of authentication, that a connecting client has a
-.B \-\-client-config-dir
-file.
-.\"*********************************************************
-.TP
-.B \-\-tmp-dir dir
-Specify a directory
-.B dir
-for temporary files.  This directory will be used by
-openvpn processes and script to communicate temporary
-data with openvpn main process. Note that
-the directory must be writable by the OpenVPN process
-after it has dropped it's root privileges.
-
-This directory will be used by in the following cases:
-
-*
-.B \-\-client-connect
-scripts to dynamically generate client-specific
-configuration files.
-
-*
-.B OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY
-plugin hook to return success/failure via auth_control_file
-when using deferred auth method
-
-*
-.B OPENVPN_PLUGIN_ENABLE_PF
-plugin hook to pass filtering rules via pf_file
-.\"*********************************************************
-.TP
-.B \-\-hash-size r v
-Set the size of the real address hash table to
-.B r
-and the virtual address table to
-.B v.
-By default, both tables are sized at 256 buckets.
-.\"*********************************************************
-.TP
-.B \-\-bcast-buffers n
-Allocate
-.B n
-buffers for broadcast datagrams (default=256).
-.\"*********************************************************
-.TP
-.B \-\-tcp-queue-limit n
-Maximum number of output packets queued before TCP (default=64).
-
-When OpenVPN is tunneling data from a TUN/TAP device to a
-remote client over a TCP connection, it is possible that the TUN/TAP device
-might produce data at a faster rate than the TCP connection
-can support.  When the number of output packets queued before sending to
-the TCP socket reaches this limit for a given client connection,
-OpenVPN will start to drop outgoing packets directed
-at this client.
-.\"*********************************************************
-.TP
-.B \-\-tcp-nodelay
-This macro sets the TCP_NODELAY socket flag on the server
-as well as pushes it to connecting clients.  The TCP_NODELAY
-flag disables the Nagle algorithm on TCP sockets causing
-packets to be transmitted immediately with low latency,
-rather than waiting a short period of time in order
-to aggregate several packets into a larger containing
-packet.  In VPN applications over TCP, TCP_NODELAY
-is generally a good latency optimization.
-
-The macro expands as follows:
-
-.nf
-.ft 3
-.in +4
- if mode server:
-   socket-flags TCP_NODELAY
-   push "socket-flags TCP_NODELAY"
-.in -4
-.ft
-.fi
-.\"*********************************************************
-.TP
-.B \-\-max-clients n
-Limit server to a maximum of
-.B n
-concurrent clients.
-.\"*********************************************************
-.TP
-.B \-\-max-routes-per-client n
-Allow a maximum of
-.B n
-internal routes per client (default=256).
-This is designed to
-help contain DoS attacks where an authenticated client floods the
-server with packets appearing to come from many unique MAC addresses,
-forcing the server to deplete
-virtual memory as its internal routing table expands.
-This directive can be used in a
-.B \-\-client-config-dir
-file or auto-generated by a
-.B \-\-client-connect
-script to override the global value for a particular client.
-
-Note that this
-directive affects OpenVPN's internal routing table, not the
-kernel routing table.
-.\"*********************************************************
-.TP
-.B \-\-connect-freq n sec
-Allow a maximum of
-.B n
-new connections per
-.B sec 
-seconds from clients.  This is designed to contain DoS attacks which flood
-the server with connection requests using certificates which
-will ultimately fail to authenticate.
-
-This is an imperfect solution however, because in a real
-DoS scenario, legitimate connections might also be refused.
-
-For the best protection against DoS attacks in server mode,
-use
-.B \-\-proto udp
-and
-.B \-\-tls-auth.
-.\"*********************************************************
-.TP
-.B \-\-learn-address cmd
-Run script or shell command
-.B cmd
-to validate client virtual addresses or routes.
-
-.B cmd
-will be executed with 3 parameters:
-
-.B [1] operation \-\-
-"add", "update", or "delete" based on whether or not
-the address is being added to, modified, or deleted from
-OpenVPN's internal routing table.
-.br
-.B [2] address \-\-
-The address being learned or unlearned.  This can be
-an IPv4 address such as "198.162.10.14", an IPv4 subnet
-such as "198.162.10.0/24", or an ethernet MAC address (when
-.B \-\-dev tap
-is being used) such as "00:FF:01:02:03:04".
-.br
-.B [3] common name \-\-
-The common name on the certificate associated with the
-client linked to this address.  Only present for "add"
-or "update" operations, not "delete".
-
-On "add" or "update" methods, if the script returns
-a failure code (non-zero), OpenVPN will reject the address
-and will not modify its internal routing table.
-
-Normally, the
-.B cmd
-script will use the information provided above to set
-appropriate firewall entries on the VPN TUN/TAP interface.
-Since OpenVPN provides the association between virtual IP
-or MAC address and the client's authenticated common name,
-it allows a user-defined script to configure firewall access
-policies with regard to the client's high-level common name,
-rather than the low level client virtual addresses.
-.\"*********************************************************
-.TP
-.B \-\-auth-user-pass-verify script method
-Require the client to provide a username/password (possibly
-in addition to a client certificate) for authentication.
-
-OpenVPN will execute
-.B script
-as a shell command to validate the username/password
-provided by the client.
-
-If
-.B method
-is set to "via-env", OpenVPN will call
-.B script
-with the environmental variables
-.B username
-and
-.B password
-set to the username/password strings provided by the client.
-Be aware that this method is insecure on some platforms which
-make the environment of a process publicly visible to other
-unprivileged processes.
-
-If
-.B method
-is set to "via-file", OpenVPN will write the username and
-password to the first two lines of a temporary file.  The filename
-will be passed as an argument to
-.B script,
-and the file will be automatically deleted by OpenVPN after
-the script returns.  The location of the temporary file is
-controlled by the
-.B \-\-tmp-dir
-option, and will default to the current directory if unspecified.
-For security, consider setting 
-.B \-\-tmp-dir
-to a volatile storage medium such as
-.B /dev/shm
-(if available) to prevent the username/password file from touching the hard drive.
-
-The script should examine the username
-and password,
-returning a success exit code (0) if the
-client's authentication request is to be accepted, or a failure
-code (1) to reject the client.
-
-This directive is designed to enable a plugin-style interface
-for extending OpenVPN's authentication capabilities.
-
-To protect against a client passing a maliciously formed
-username or password string, the username string must
-consist only of these characters: alphanumeric, underbar
-('_'), dash ('-'), dot ('.'), or at ('@').  The password
-string can consist of any printable characters except for
-CR or LF.  Any illegal characters in either the username
-or password string will be converted to underbar ('_').
-
-Care must be taken by any user-defined scripts to avoid
-creating a security vulnerability in the way that these
-strings are handled.  Never use these strings in such a way
-that they might be escaped or evaluated by a shell interpreter.
-
-For a sample script that performs PAM authentication, see
-.B sample-scripts/auth-pam.pl
-in the OpenVPN source distribution.
-.\"*********************************************************
-.TP
-.B \-\-opt-verify
-Clients that connect with options that are incompatible
-with those of the server will be disconnected.
-
-Options that will be compared for compatibility include
-dev-type, link-mtu, tun-mtu, proto, tun-ipv6, ifconfig,
-comp-lzo, fragment, keydir, cipher, auth, keysize, secret,
-no-replay, no-iv, tls-auth, key-method, tls-server, and tls-client.
-
-This option requires that
-.B \-\-disable-occ
-NOT be used.
-.\"*********************************************************
-.TP
-.B \-\-auth-user-pass-optional
-Allow connections by clients that do not specify a username/password.
-Normally, when
-.B \-\-auth-user-pass-verify
-or
-.B \-\-management-client-auth
-is specified (or an authentication plugin module), the
-OpenVPN server daemon will require connecting clients to specify a
-username and password.  This option makes the submission of a username/password
-by clients optional, passing the responsibility to the user-defined authentication
-module/script to accept or deny the client based on other factors
-(such as the setting of X509 certificate fields).  When this option is used,
-and a connecting client does not submit a username/password, the user-defined
-authentication module/script will see the username and password as being set
-to empty strings ("").  The authentication module/script MUST have logic
-to detect this condition and respond accordingly.
-.\"*********************************************************
-.TP
-.B \-\-client-cert-not-required
-Don't require client certificate, client will authenticate
-using username/password only.  Be aware that using this directive
-is less secure than requiring certificates from all clients.
-
-If you use this directive, the
-entire responsibility of authentication will rest on your
-.B \-\-auth-user-pass-verify
-script, so keep in mind that bugs in your script
-could potentially compromise the security of your VPN.
-
-If you don't use this directive, but you also specify an
-.B \-\-auth-user-pass-verify
-script, then OpenVPN will perform double authentication.  The
-client certificate verification AND the
-.B \-\-auth-user-pass-verify
-script will need to succeed in order for a client to be
-authenticated and accepted onto the VPN.
-.\"*********************************************************
-.TP
-.B \-\-username-as-common-name
-For
-.B \-\-auth-user-pass-verify
-authentication, use
-the authenticated username as the common name,
-rather than the common name from the client cert.
-.\"*********************************************************
-.TP
-.B \-\-no-name-remapping
-Allow Common Name, X509 Subject, and username strings to include
-any printable character including space, but excluding control
-characters such as tab, newline, and carriage-return.
-
-By default, OpenVPN will remap
-any character other than alphanumeric, underbar ('_'), dash
-('-'), dot ('.'), and slash ('/') to underbar ('_').  The X509
-Subject string as returned by the
-.B tls_id
-environmental variable, can additionally contain colon (':') or
-equal ('=').
-
-While name remapping is performed for security reasons to reduce
-the possibility of introducing string expansion security vulnerabilities
-in user-defined authentication
-scripts, this option is provided for those cases where it is desirable to
-disable the remapping feature.  Don't use this option unless you 
-know what you are doing!
-.\"*********************************************************
-.TP
-.B \-\-port-share host port
-When run in TCP server mode, share the OpenVPN port with
-another application, such as an HTTPS server.  If OpenVPN
-senses a connection to its port which is using a non-OpenVPN
-protocol, it will proxy the connection to the server at
-.B host:port.
-Currently only designed to work with HTTP/HTTPS,
-though it would be theoretically possible to extend to
-other protocols such as ssh.
-
-Not implemented on Windows.
-.\"*********************************************************
-.SS Client Mode
-Use client mode when connecting to an OpenVPN server
-which has
-.B \-\-server, \-\-server-bridge,
-or
-.B \-\-mode server
-in it's configuration.
-.\"*********************************************************
-.TP
-.B \-\-client
-A helper directive designed to simplify the configuration
-of OpenVPN's client mode.  This directive is equivalent to:
-
-.nf
-.ft 3
-.in +4
- pull
- tls-client
-.in -4
-.ft
-.fi
-.\"*********************************************************
-.TP
-.B \-\-pull
-This option must be used on a client which is connecting
-to a multi-client server.  It indicates to OpenVPN that it
-should accept options pushed by the server, provided they
-are part of the legal set of pushable options (note that the
-.B \-\-pull
-option is implied by
-.B \-\-client
-).
-
-In particular,
-.B \-\-pull
-allows the server to push routes to the client, so you should
-not use
-.B \-\-pull
-or
-.B \-\-client
-in situations where you don't trust the server to have control
-over the client's routing table.
-.\"*********************************************************
-.TP
-.B \-\-auth-user-pass [up]
-Authenticate with server using username/password.
-.B up
-is a file containing username/password on 2 lines (Note: OpenVPN
-will only read passwords from a file if it has been built
-with the \-\-enable-password-save configure option, or on Windows
-by defining ENABLE_PASSWORD_SAVE in win/settings.in).
-
-If
-.B up
-is omitted, username/password will be prompted from the
-console.
-
-The server configuration must specify an
-.B \-\-auth-user-pass-verify
-script to verify the username/password provided by
-the client.
-.\"*********************************************************
-.TP
-.B \-\-auth-retry type
-Controls how OpenVPN responds to username/password verification
-errors such as the client-side response to an AUTH_FAILED message from the server
-or verification failure of the private key password.
-
-Normally used to prevent auth errors from being fatal
-on the client side, and to permit username/password requeries in case
-of error.
-
-An AUTH_FAILED message is generated by the server if the client
-fails
-.B \-\-auth-user-pass
-authentication, or if the server-side
-.B \-\-client-connect
-script returns an error status when the client
-tries to connect.
-
-.B type
-can be one of:
-
-.B none \-\-
-Client will exit with a fatal error (this is the default).
-.br
-.B nointeract \-\-
-Client will retry the connection without requerying for an
-.B \-\-auth-user-pass
-username/password.  Use this option for unattended clients.
-.br
-.B interact \-\-
-Client will requery for an
-.B \-\-auth-user-pass
-username/password and/or private key password before attempting a reconnection.
-
-Note that while this option cannot be pushed, it can be controlled
-from the management interface.
-.\"*********************************************************
-.TP
-.B \-\-server-poll-timeout n
-when polling possible remote servers to connect to
-in a round-robin fashion, spend no more than
-.B n
-seconds waiting for a response before trying the next server.
-.\"*********************************************************
-.TP
-.B \-\-explicit-exit-notify [n]
-In UDP client mode or point-to-point mode, send server/peer an exit notification
-if tunnel is restarted or OpenVPN process is exited.  In client mode, on
-exit/restart, this
-option will tell the server to immediately close its client instance object
-rather than waiting for a timeout.  The
-.B n
-parameter (default=1) controls the maximum number of attempts that the client
-will try to resend the exit notification message.  OpenVPN will not send any exit
-notifications unless this option is enabled.
-.\"*********************************************************
-.SS Data Channel Encryption Options:
-These options are meaningful for both Static & TLS-negotiated key modes
-(must be compatible between peers).
-.\"*********************************************************
-.TP
-.B \-\-secret file [direction]
-Enable Static Key encryption mode (non-TLS).
-Use pre-shared secret
-.B file
-which was generated with
-.B \-\-genkey.
-
-The optional
-.B direction
-parameter enables the use of 4 distinct keys
-(HMAC-send, cipher-encrypt, HMAC-receive, cipher-decrypt), so that
-each data flow direction has a different set of HMAC and cipher keys.
-This has a number of desirable security properties including
-eliminating certain kinds of DoS and message replay attacks.
-
-When the
-.B direction
-parameter is omitted, 2 keys are used bidirectionally, one for HMAC
-and the other for encryption/decryption.
-
-The
-.B direction
-parameter should always be complementary on either side of the connection,
-i.e. one side should use "0" and the other should use "1", or both sides
-should omit it altogether.
-
-The
-.B direction
-parameter requires that
-.B file
-contains a 2048 bit key.  While pre-1.5 versions of OpenVPN
-generate 1024 bit key files, any version of OpenVPN which
-supports the
-.B direction
-parameter, will also support 2048 bit key file generation
-using the
-.B \-\-genkey
-option.
-
-Static key encryption mode has certain advantages,
-the primary being ease of configuration.
-
-There are no certificates
-or certificate authorities or complicated negotiation handshakes and protocols.
-The only requirement is that you have a pre-existing secure channel with
-your peer (such as
-.B ssh
-) to initially copy the key.  This requirement, along with the
-fact that your key never changes unless you manually generate a new one,
-makes it somewhat less secure than TLS mode (see below).  If an attacker
-manages to steal your key, everything that was ever encrypted with
-it is compromised.  Contrast that to the perfect forward secrecy features of
-TLS mode (using Diffie Hellman key exchange), where even if an attacker
-was able to steal your private key, he would gain no information to help
-him decrypt past sessions.
-
-Another advantageous aspect of Static Key encryption mode is that
-it is a handshake-free protocol 
-without any distinguishing signature or feature
-(such as a header or protocol handshake sequence) 
-that would mark the ciphertext packets as being
-generated by OpenVPN.  Anyone eavesdropping on the wire
-would see nothing
-but random-looking data.
-.\"*********************************************************
-.TP
-.B \-\-auth alg
-Authenticate packets with HMAC using message
-digest algorithm
-.B alg.
-(The default is
-.B SHA1
-).
-HMAC is a commonly used message authentication algorithm (MAC) that uses
-a data string, a secure hash algorithm, and a key, to produce
-a digital signature.
-
-OpenVPN's usage of HMAC is to first encrypt a packet, then HMAC the resulting ciphertext.
-
-In static-key encryption mode, the HMAC key
-is included in the key file generated by
-.B \-\-genkey.
-In TLS mode, the HMAC key is dynamically generated and shared
-between peers via the TLS control channel.  If OpenVPN receives a packet with
-a bad HMAC it will drop the packet.
-HMAC usually adds 16 or 20 bytes per packet.
-Set
-.B alg=none
-to disable authentication.
-
-For more information on HMAC see
-.I http://www.cs.ucsd.edu/users/mihir/papers/hmac.html
-.\"*********************************************************
-.TP
-.B \-\-cipher alg
-Encrypt packets with cipher algorithm
-.B alg.
-The default is
-.B BF-CBC,
-an abbreviation for Blowfish in Cipher Block Chaining mode.
-Blowfish has the advantages of being fast, very secure, and allowing key sizes
-of up to 448 bits.  Blowfish is designed to be used in situations where
-keys are changed infrequently.
-
-For more information on blowfish, see
-.I http://www.counterpane.com/blowfish.html
-
-To see other ciphers that are available with
-OpenVPN, use the
-.B \-\-show-ciphers
-option.
-
-OpenVPN supports the CBC, CFB, and OFB cipher modes,
-however CBC is recommended and CFB and OFB should
-be considered advanced modes.
-
-Set
-.B alg=none
-to disable encryption.
-.\"*********************************************************
-.TP
-.B \-\-keysize n
-Size of cipher key in bits (optional).
-If unspecified, defaults to cipher-specific default.  The
-.B \-\-show-ciphers
-option (see below) shows all available OpenSSL ciphers,
-their default key sizes, and whether the key size can
-be changed.  Use care in changing a cipher's default
-key size.  Many ciphers have not been extensively
-cryptanalyzed with non-standard key lengths, and a
-larger key may offer no real guarantee of greater
-security, or may even reduce security.
-.\"*********************************************************
-.TP
-.B \-\-prng alg [nsl]
-(Advanced) For PRNG (Pseudo-random number generator),
-use digest algorithm
-.B alg
-(default=sha1), and set
-.B nsl
-(default=16)
-to the size in bytes of the nonce secret length (between 16 and 64).
-
-Set
-.B alg=none
-to disable the PRNG and use the OpenSSL RAND_bytes function
-instead for all of OpenVPN's pseudo-random number needs.
-.\"*********************************************************
-.TP
-.B \-\-engine [engine-name]
-Enable OpenSSL hardware-based crypto engine functionality.
-
-If
-.B engine-name
-is specified,
-use a specific crypto engine.  Use the
-.B \-\-show-engines
-standalone option to list the crypto engines which are
-supported by OpenSSL.
-.\"*********************************************************
-.TP
-.B \-\-no-replay
-(Advanced) Disable OpenVPN's protection against replay attacks.
-Don't use this option unless you are prepared to make
-a tradeoff of greater efficiency in exchange for less
-security.
-
-OpenVPN provides datagram replay protection by default.
-
-Replay protection is accomplished
-by tagging each outgoing datagram with an identifier
-that is guaranteed to be unique for the key being used.
-The peer that receives the datagram will check for
-the uniqueness of the identifier.  If the identifier
-was already received in a previous datagram, OpenVPN
-will drop the packet.  Replay protection is important
-to defeat attacks such as a SYN flood attack, where
-the attacker listens in the wire, intercepts a TCP
-SYN packet (identifying it by the context in which
-it occurs in relation to other packets), then floods
-the receiving peer with copies of this packet.
-
-OpenVPN's replay protection is implemented in slightly
-different ways, depending on the key management mode
-you have selected.
-
-In Static Key mode
-or when using an CFB or OFB mode cipher, OpenVPN uses a
-64 bit unique identifier that combines a time stamp with
-an incrementing sequence number.
-
-When using TLS mode for key exchange and a CBC cipher
-mode, OpenVPN uses only a 32 bit sequence number without
-a time stamp, since OpenVPN can guarantee the uniqueness
-of this value for each key.  As in IPSec, if the sequence number is
-close to wrapping back to zero, OpenVPN will trigger
-a new key exchange.
-
-To check for replays, OpenVPN uses
-the
-.I sliding window
-algorithm used
-by IPSec.
-.\"*********************************************************
-.TP
-.B \-\-replay-window n [t]
-Use a replay protection sliding-window of size
-.B n
-and a time window of
-.B t
-seconds.
-
-By default
-.B n
-is 64 (the IPSec default) and
-.B t
-is 15 seconds.
-
-This option is only relevant in UDP mode, i.e.
-when either
-.B \-\-proto udp
-is specifed, or no
-.B \-\-proto
-option is specified.
-
-When OpenVPN tunnels IP packets over UDP, there is the possibility that
-packets might be dropped or delivered out of order.  Because OpenVPN, like IPSec,
-is emulating the physical network layer,
-it will accept an out-of-order packet sequence, and
-will deliver such packets in the same order they were received to
-the TCP/IP protocol stack, provided they satisfy several constraints.
-
-.B (a)
-The packet cannot be a replay (unless
-.B \-\-no-replay
-is specified, which disables replay protection altogether).
-
-.B (b)
-If a packet arrives out of order, it will only be accepted if the difference
-between its sequence number and the highest sequence number received
-so far is less than
-.B n.
-
-.B (c)
-If a packet arrives out of order, it will only be accepted if it arrives no later
-than
-.B t
-seconds after any packet containing a higher sequence number.
-
-If you are using a network link with a large pipeline (meaning that
-the product of bandwidth and latency is high), you may want to use
-a larger value for
-.B n.
-Satellite links in particular often require this.
-
-If you run OpenVPN at
-.B \-\-verb 4,
-you will see the message "Replay-window backtrack occurred [x]"
-every time the maximum sequence number backtrack seen thus far
-increases.  This can be used to calibrate
-.B n.
-
-There is some controversy on the appropriate method of handling packet
-reordering at the security layer.
-
-Namely, to what extent should the
-security layer protect the encapsulated protocol from attacks which masquerade
-as the kinds of normal packet loss and reordering that occur over IP networks?
-
-The IPSec and OpenVPN approach is to allow packet reordering within a certain
-fixed sequence number window.
-
-OpenVPN adds to the IPSec model by limiting the window size in time as well as
-sequence space.
-
-OpenVPN also adds TCP transport as an option (not offered by IPSec) in which
-case OpenVPN can adopt a very strict attitude towards message deletion and
-reordering:  Don't allow it.  Since TCP guarantees reliability, any packet
-loss or reordering event can be assumed to be an attack.
-
-In this sense, it could be argued that TCP tunnel transport is preferred when
-tunneling non-IP or UDP application protocols which might be vulnerable to a
-message deletion or reordering attack which falls within the normal
-operational parameters of IP networks.
-
-So I would make the statement that one should never tunnel a non-IP protocol
-or UDP application protocol over UDP, if the protocol might be vulnerable to a
-message deletion or reordering attack that falls within the normal operating
-parameters of what is to be expected from the physical IP layer.  The problem
-is easily fixed by simply using TCP as the VPN transport layer.
-.\"*********************************************************
-.TP
-.B \-\-mute-replay-warnings
-Silence the output of replay warnings, which are a common
-false alarm on WiFi networks.  This option preserves
-the security of the replay protection code without
-the verbosity associated with warnings about duplicate
-packets.
-.\"*********************************************************
-.TP
-.B \-\-replay-persist file
-Persist replay-protection state across sessions using
-.B file
-to save and reload the state.
-
-This option will strengthen protection against replay attacks,
-especially when you are using OpenVPN in a dynamic context (such
-as with
-.B \-\-inetd)
-when OpenVPN sessions are frequently started and stopped. 
-
-This option will keep a disk copy of the current replay protection
-state (i.e. the most recent packet timestamp and sequence number
-received from the remote peer), so that if an OpenVPN session
-is stopped and restarted, it will reject any replays of packets
-which were already received by the prior session.
-
-This option only makes sense when replay protection is enabled
-(the default) and you are using either
-.B \-\-secret
-(shared-secret key mode) or TLS mode with
-.B \-\-tls-auth.
-.\"*********************************************************
-.TP
-.B \-\-no-iv
-(Advanced) Disable OpenVPN's use of IV (cipher initialization vector).
-Don't use this option unless you are prepared to make
-a tradeoff of greater efficiency in exchange for less
-security.
-
-OpenVPN uses an IV by default, and requires it for CFB and
-OFB cipher modes (which are totally insecure without it).
-Using an IV is important for security when multiple
-messages are being encrypted/decrypted with the same key.
-
-IV is implemented differently depending on the cipher mode used.
-
-In CBC mode, OpenVPN uses a pseudo-random IV for each packet.
-
-In CFB/OFB mode, OpenVPN uses a unique sequence number and time stamp
-as the IV.  In fact, in CFB/OFB mode, OpenVPN uses a datagram
-space-saving optimization that uses the unique identifier for
-datagram replay protection as the IV.
-.\"*********************************************************
-.TP
-.B \-\-test-crypto
-Do a self-test of OpenVPN's crypto options by encrypting and
-decrypting test packets using the data channel encryption options
-specified above.  This option does not require a peer to function,
-and therefore can be specified without
-.B \-\-dev
-or
-.B \-\-remote.
-
-The typical usage of
-.B \-\-test-crypto
-would be something like this:
-
-.B openvpn \-\-test-crypto \-\-secret key
-
-or
-
-.B openvpn \-\-test-crypto \-\-secret key \-\-verb 9
-
-This option is very useful to test OpenVPN after it has been ported to
-a new platform, or to isolate problems in the compiler, OpenSSL
-crypto library, or OpenVPN's crypto code.  Since it is a self-test mode,
-problems with encryption and authentication can be debugged independently
-of network and tunnel issues.
-.\"*********************************************************
-.SS TLS Mode Options:
-TLS mode is the most powerful crypto mode of OpenVPN in both security and flexibility.
-TLS mode works by establishing control and
-data channels which are multiplexed over a single TCP/UDP port.  OpenVPN initiates
-a TLS session over the control channel and uses it to exchange cipher
-and HMAC keys to protect the data channel.  TLS mode uses a robust reliability
-layer over the UDP connection for all control channel communication, while
-the data channel, over which encrypted tunnel data passes, is forwarded without
-any mediation.  The result is the best of both worlds: a fast data channel
-that forwards over UDP with only the overhead of encrypt,
-decrypt, and HMAC functions,
-and a control channel that provides all of the security features of TLS,
-including certificate-based authentication and Diffie Hellman forward secrecy.
-
-To use TLS mode, each peer that runs OpenVPN should have its own local
-certificate/key pair (
-.B \-\-cert
-and
-.B \-\-key
-), signed by the root certificate which is specified
-in
-.B \-\-ca.
-
-When two OpenVPN peers connect, each presents its local certificate to the
-other.  Each peer will then check that its partner peer presented a
-certificate which was signed by the master root certificate as specified in
-.B \-\-ca.
-
-If that check on both peers succeeds, then the TLS negotiation
-will succeed, both OpenVPN
-peers will exchange temporary session keys, and the tunnel will begin
-passing data.
-
-The OpenVPN distribution contains a set of scripts for
-managing RSA certificates & keys,
-located in the
-.I easy-rsa
-subdirectory.
-
-The easy-rsa package is also rendered in web form here:
-.I http://openvpn.net/easyrsa.html
-.\"*********************************************************
-.TP
-.B \-\-tls-server
-Enable TLS and assume server role during TLS handshake.  Note that
-OpenVPN is designed as a peer-to-peer application.  The designation
-of client or server is only for the purpose of negotiating the TLS
-control channel.
-.\"*********************************************************
-.TP
-.B \-\-tls-client
-Enable TLS and assume client role during TLS handshake.
-.\"*********************************************************
-.TP
-.B \-\-ca file
-Certificate authority (CA) file in .pem format, also referred to as the
-.I root
-certificate.  This file can have multiple
-certificates in .pem format, concatenated together.  You can construct your own
-certificate authority certificate and private key by using a command such as:
-
-.B openssl req -nodes -new -x509 -keyout ca.key -out ca.crt
-
-Then edit your openssl.cnf file and edit the
-.B certificate
-variable to point to your new root certificate
-.B ca.crt.
-
-For testing purposes only, the OpenVPN distribution includes a sample
-CA certificate (ca.crt).
-Of course you should never use
-the test certificates and test keys distributed with OpenVPN in a
-production environment, since by virtue of the fact that
-they are distributed with OpenVPN, they are totally insecure.
-.\"*********************************************************
-.TP
-.B \-\-capath dir
-Directory containing trusted certificates (CAs and CRLs).
-Available with OpenSSL version >= 0.9.7 dev.
-.\"*********************************************************
-.TP
-.B \-\-dh file
-File containing Diffie Hellman parameters
-in .pem format (required for
-.B \-\-tls-server
-only). Use
-
-.B openssl dhparam -out dh1024.pem 1024
-
-to generate your own, or use the existing dh1024.pem file
-included with the OpenVPN distribution.  Diffie Hellman parameters
-may be considered public.
-.\"*********************************************************
-.TP
-.B \-\-cert file
-Local peer's signed certificate in .pem format \-\- must be signed
-by a certificate authority whose certificate is in
-.B \-\-ca file.
-Each peer in an OpenVPN link running in TLS mode should have its own
-certificate and private key file.  In addition, each certificate should
-have been signed by the key of a certificate
-authority whose public key resides in the
-.B \-\-ca
-certificate authority file.
-You can easily make your own certificate authority (see above) or pay money
-to use a commercial service such as thawte.com (in which case you will be
-helping to finance the world's second space tourist :).
-To generate a certificate,
-you can use a command such as:
-
-.B openssl req -nodes -new -keyout mycert.key -out mycert.csr
-
-If your certificate authority private key lives on another machine, copy
-the certificate signing request (mycert.csr) to this other machine (this can
-be done over an insecure channel such as email).  Now sign the certificate
-with a command such as:
-
-.B openssl ca -out mycert.crt -in mycert.csr
-
-Now copy the certificate (mycert.crt)
-back to the peer which initially generated the .csr file (this
-can be over a public medium).
-Note that the
-.B openssl ca
-command reads the location of the certificate authority key from its
-configuration file such as
-.B /usr/share/ssl/openssl.cnf
-\-\- note also
-that for certificate authority functions, you must set up the files
-.B index.txt
-(may be empty) and
-.B serial
-(initialize to
-.B 
-01
-).
-.\"*********************************************************
-.TP
-.B \-\-key file
-Local peer's private key in .pem format.  Use the private key which was generated
-when you built your peer's certificate (see
-.B -cert file
-above).
-.\"*********************************************************
-.TP
-.B \-\-pkcs12 file
-Specify a PKCS #12 file containing local private key,
-local certificate, and root CA certificate.
-This option can be used instead of
-.B \-\-ca, \-\-cert,
-and
-.B \-\-key.
-.\"*********************************************************
-.TP
-.B \-\-pkcs11-cert-private [0|1]...
-Set if access to certificate object should be performed after login.
-Every provider has its own setting.
-.\"*********************************************************
-.TP
-.B \-\-pkcs11-id name
-Specify the serialized certificate id to be used. The id can be gotten
-by the standalone
-.B \-\-show-pkcs11-ids
-option.
-.\"*********************************************************
-.TP
-.B \-\-pkcs11-id-management
-Acquire PKCS#11 id from management interface. In this case a NEED-STR 'pkcs11-id-request'
-real-time message will be triggered, application may use pkcs11-id-count command to
-retrieve available number of certificates, and pkcs11-id-get command to retrieve certificate
-id and certificate body.
-.\"*********************************************************
-.TP
-.B \-\-pkcs11-pin-cache seconds
-Specify how many seconds the PIN can be cached, the default is until the token is removed.
-.\"*********************************************************
-.TP
-.B \-\-pkcs11-protected-authentication [0|1]...
-Use PKCS#11 protected authentication path, useful for biometric and external
-keypad devices.
-Every provider has its own setting.
-.\"*********************************************************
-.TP
-.B \-\-pkcs11-providers provider...
-Specify a RSA Security Inc. PKCS #11 Cryptographic Token Interface (Cryptoki) providers
-to load.
-This option can be used instead of
-.B \-\-cert, \-\-key,
-and
-.B \-\-pkcs12.
-.\"*********************************************************
-.TP
-.B \-\-pkcs11-private-mode mode...
-Specify which method to use in order to perform private key operations.
-A different mode can be specified for each provider.
-Mode is encoded as hex number, and can be a mask one of the following:
-
-.B 0
-(default) \-\- Try to determind automatically.
-.br
-.B 1
-\-\- Use sign.
-.br
-.B 2
-\-\- Use sign recover.
-.br
-.B 4
-\-\- Use decrypt.
-.br
-.B 8
-\-\- Use unwrap.
-.br
-.\"*********************************************************
-.TP
-.B \-\-cryptoapicert select-string
-Load the certificate and private key from the
-Windows Certificate System Store (Windows Only).
-
-Use this option instead of
-.B \-\-cert
-and
-.B \-\-key.
-
-This makes
-it possible to use any smart card, supported by Windows, but also any
-kind of certificate, residing in the Cert Store, where you have access to
-the private key.  This option has been tested with a couple of different
-smart cards (GemSAFE, Cryptoflex, and Swedish Post Office eID) on the
-client side, and also an imported PKCS12 software certificate on the
-server side.
-
-To select a certificate, based on a substring search in the
-certificate's subject:
-
-.B cryptoapicert
-"SUBJ:Peter Runestig"
-
-To select a certificate, based on certificate's thumbprint:
-
-.B cryptoapicert
-"THUMB:f6 49 24 41 01 b4 ..."
-
-The thumbprint hex string can easily be copy-and-pasted from the Windows
-Certificate Store GUI.
-
-.\"*********************************************************
-.TP
-.B \-\-key-method m
-Use data channel key negotiation method
-.B m.
-The key method must match on both sides of the connection.
-
-After OpenVPN negotiates a TLS session, a new set of keys
-for protecting the tunnel data channel is generated and
-exchanged over the TLS session.
-
-In method 1 (the default for OpenVPN 1.x), both sides generate
-random encrypt and HMAC-send keys which are forwarded to
-the other host over the TLS channel.
-
-In method 2, (the default for OpenVPN 2.0)
-the client generates a random key.  Both client
-and server also generate some random seed material.  All key source
-material is exchanged over the TLS channel. The actual
-keys are generated using the TLS PRF function, taking source
-entropy from both client and server.  Method 2 is designed to
-closely parallel the key generation process used by TLS 1.0.
-
-Note that in TLS mode, two separate levels 
-of keying occur:
-
-(1) The TLS connection is initially negotiated, with both sides
-of the connection producing certificates and verifying the certificate
-(or other authentication info provided) of
-the other side.  The
-.B \-\-key-method
-parameter has no effect on this process.
-
-(2) After the TLS connection is established, the tunnel session keys are
-separately negotiated over the existing secure TLS channel.  Here,
-.B \-\-key-method
-determines the derivation of the tunnel session keys.
-.\"*********************************************************
-.TP
-.B \-\-tls-cipher l
-A list
-.B l
-of allowable TLS ciphers delimited by a colon (":").
-If you require a high level of security,
-you may want to set this parameter manually, to prevent a
-version rollback attack where a man-in-the-middle attacker tries
-to force two peers to negotiate to the lowest level
-of security they both support.
-Use
-.B \-\-show-tls
-to see a list of supported TLS ciphers.
-.\"*********************************************************
-.TP
-.B \-\-tls-timeout n
-Packet retransmit timeout on TLS control channel
-if no acknowledgment from remote within
-.B n
-seconds (default=2).  When OpenVPN sends a control
-packet to its peer, it will expect to receive an
-acknowledgement within
-.B n
-seconds or it will retransmit the packet, subject
-to a TCP-like exponential backoff algorithm.  This parameter
-only applies to control channel packets.  Data channel
-packets (which carry encrypted tunnel data) are never
-acknowledged, sequenced, or retransmitted by OpenVPN because
-the higher level network protocols running on top of the tunnel
-such as TCP expect this role to be left to them.
-.\"*********************************************************
-.TP
-.B \-\-reneg-bytes n
-Renegotiate data channel key after
-.B n
-bytes sent or received (disabled by default).
-OpenVPN allows the lifetime of a key
-to be expressed as a number of bytes encrypted/decrypted, a number of packets, or
-a number of seconds.  A key renegotiation will be forced
-if any of these three criteria are met by either peer.
-.\"*********************************************************
-.TP
-.B \-\-reneg-pkts n
-Renegotiate data channel key after
-.B n
-packets sent and received (disabled by default).
-.\"*********************************************************
-.TP
-.B \-\-reneg-sec n
-Renegotiate data channel key after
-.B n
-seconds (default=3600).
-
-When using dual-factor authentication, note that this default value may
-cause the end user to be challenged to reauthorize once per hour.
-
-Also, keep in mind that this option can be used on both the client and server,
-and whichever uses the lower value will be the one to trigger the renegotiation.
-A common mistake is to set
-.B \-\-reneg-sec
-to a higher value on either the client or server, while the other side of the connection
-is still using the default value of 3600 seconds, meaning that the renegotiation will
-still occur once per 3600 seconds.  The solution is to increase \-\-reneg-sec on both the
-client and server, or set it to 0 on one side of the connection (to disable), and to
-your chosen value on the other side.
-.\"*********************************************************
-.TP
-.B \-\-hand-window n
-Handshake Window \-\- the TLS-based key exchange must finalize within
-.B n
-seconds
-of handshake initiation by any peer (default = 60 seconds).
-If the handshake fails
-we will attempt to reset our connection with our peer and try again.
-Even in the event of handshake failure we will still use
-our expiring key for up to
-.B \-\-tran-window
-seconds to maintain continuity of transmission of tunnel
-data.
-.\"*********************************************************
-.TP
-.B \-\-tran-window n
-Transition window \-\- our old key can live this many seconds
-after a new a key renegotiation begins (default = 3600 seconds).
-This feature allows for a graceful transition from old to new
-key, and removes the key renegotiation sequence from the critical
-path of tunnel data forwarding.
-.\"*********************************************************
-.TP
-.B \-\-single-session
-After initially connecting to a remote peer, disallow any new connections.
-Using this
-option means that a remote peer cannot connect, disconnect, and then
-reconnect.
-
-If the daemon is reset by a signal or
-.B \-\-ping-restart,
-it will allow one new connection.
-
-.B \-\-single-session
-can be used with
-.B \-\-ping-exit
-or
-.B \-\-inactive
-to create a single dynamic session that will exit when finished.
-.\"*********************************************************
-.TP
-.B \-\-tls-exit
-Exit on TLS negotiation failure.
-.\"*********************************************************
-.TP
-.B \-\-tls-auth file [direction]
-Add an additional layer of HMAC authentication on top of the TLS
-control channel to protect against DoS attacks.
-
-In a nutshell,
-.B \-\-tls-auth
-enables a kind of "HMAC firewall" on OpenVPN's TCP/UDP port,
-where TLS control channel packets
-bearing an incorrect HMAC signature can be dropped immediately without
-response.
-
-.B file
-(required) is a key file which can be in one of two formats:
-
-.B (1)
-An OpenVPN static key file generated by
-.B \-\-genkey
-(required if
-.B direction
-parameter is used).
-
-.B (2)
-A freeform passphrase file.  In this case the HMAC key will
-be derived by taking a secure hash of this file, similar to
-the
-.BR md5sum (1)
-or
-.BR sha1sum (1)
-commands.
-
-OpenVPN will first try format (1), and if the file fails to parse as
-a static key file, format (2) will be used.
-
-See the
-.B \-\-secret
-option for more information on the optional
-.B direction
-parameter.
-
-.B \-\-tls-auth
-is recommended when you are running OpenVPN in a mode where
-it is listening for packets from any IP address, such as when
-.B \-\-remote
-is not specified, or
-.B \-\-remote
-is specified with
-.B \-\-float.
-
-The rationale for
-this feature is as follows.  TLS requires a multi-packet exchange
-before it is able to authenticate a peer.  During this time
-before authentication, OpenVPN is allocating resources (memory
-and CPU) to this potential peer.  The potential peer is also
-exposing many parts of OpenVPN and the OpenSSL library to the packets
-it is sending.  Most successful network attacks today seek
-to either exploit bugs in programs (such as buffer overflow attacks) or
-force a program to consume so many resources that it becomes unusable.
-Of course the first line of defense is always to produce clean,
-well-audited code.  OpenVPN has been written with buffer overflow
-attack prevention as a top priority.
-But as history has shown, many of the most widely used
-network applications have, from time to time,
-fallen to buffer overflow attacks.
-
-So as a second line of defense, OpenVPN offers
-this special layer of authentication on top of the TLS control channel so that
-every packet on the control channel is authenticated by an
-HMAC signature and a unique ID for replay protection.
-This signature will also help protect against DoS (Denial of Service) attacks.
-An important rule of thumb in reducing vulnerability to DoS attacks is to
-minimize the amount of resources a potential, but as yet unauthenticated,
-client is able to consume.
-
-.B \-\-tls-auth
-does this by signing every TLS control channel packet with an HMAC signature,
-including packets which are sent before the TLS level has had a chance
-to authenticate the peer.
-The result is that packets without
-the correct signature can be dropped immediately upon reception,
-before they have a chance to consume additional system resources
-such as by initiating a TLS handshake.
-.B \-\-tls-auth
-can be strengthened by adding the
-.B \-\-replay-persist
-option which will keep OpenVPN's replay protection state
-in a file so that it is not lost across restarts.
-
-It should be emphasized that this feature is optional and that the
-passphrase/key file used with
-.B \-\-tls-auth
-gives a peer nothing more than the power to initiate a TLS
-handshake.  It is not used to encrypt or authenticate any tunnel data.
-.\"*********************************************************
-.TP
-.B \-\-askpass [file]
-Get certificate password from console or
-.B file
-before we daemonize.
-
-For the extremely
-security conscious, it is possible to protect your private key with
-a password.  Of course this means that every time the OpenVPN
-daemon is started you must be there to type the password.  The
-.B \-\-askpass
-option allows you to start OpenVPN from the command line.  It will
-query you for a password before it daemonizes.  To protect a private
-key with a password you should omit the
-.B -nodes
-option when you use the
-.B openssl
-command line tool to manage certificates and private keys.
-
-If
-.B file
-is specified, read the password from the first line of
-.B file.
-Keep in mind that storing your password in a file
-to a certain extent invalidates the extra security provided by
-using an encrypted key (Note: OpenVPN
-will only read passwords from a file if it has been built
-with the \-\-enable-password-save configure option, or on Windows
-by defining ENABLE_PASSWORD_SAVE in win/settings.in).
-.\"*********************************************************
-.TP
-.B \-\-auth-nocache
-Don't cache
-.B \-\-askpass
-or
-.B \-\-auth-user-pass
-username/passwords in virtual memory.
-
-If specified, this directive will cause OpenVPN to immediately
-forget username/password inputs after they are used.  As a result,
-when OpenVPN needs a username/password, it will prompt for input
-from stdin, which may be multiple times during the duration of an
-OpenVPN session.
-
-This directive does not affect the
-.B \-\-http-proxy
-username/password.  It is always cached.
-.\"*********************************************************
-.TP
-.B \-\-tls-verify cmd
-Execute shell command
-.B cmd
-to verify the X509 name of a
-pending TLS connection that has otherwise passed all other
-tests of certification (except for revocation via
-.B \-\-crl-verify
-directive; the revocation test occurs after the
-.B \-\-tls-verify
-test).
-
-.B cmd
-should return 0 to allow the TLS handshake to proceed, or 1 to fail.
-
-Note that
-.B cmd
-is a command line and as such may (if enclosed in quotes) contain
-whitespace separated arguments.  The first word of
-.B cmd
-is the shell command to execute and the remaining words are its
-arguments.
-When
-.B cmd
-is executed two arguments are appended, as follows:
-
-.B cmd certificate_depth X509_NAME_oneline
-
-These arguments are, respectively, the current certificate depth and
-the X509 common name (cn) of the peer.
-
-This feature is useful if the peer you want to trust has a certificate
-which was signed by a certificate authority who also signed many
-other certificates, where you don't necessarily want to trust all of them,
-but rather be selective about which
-peer certificate you will accept.  This feature allows you to write a script
-which will test the X509 name on a certificate and decide whether or
-not it should be accepted.  For a simple perl script which will test
-the common name field on the certificate, see the file
-.B verify-cn
-in the OpenVPN distribution.
-
-See the "Environmental Variables" section below for
-additional parameters passed as environmental variables.
-.\"*********************************************************
-.TP
-.B \-\-tls-export-cert directory
-Store the certificates the clients uses upon connection to this
-directory. This will be done before --tls-verify is called.  The
-certificates will use a temporary name and will be deleted when
-the tls-verify script returns.  The file name used for the certificate
-is available via the peer_cert environment variable.
-.\"*********************************************************
-.TP
-.B \-\-x509-username-field fieldname
-Field in x509 certificate subject to be used as username (default=CN).
-.B Fieldname
-will be uppercased before matching. When this option is used, the
---tls-remote option will match against the chosen fieldname instead
-of the CN.
-.\"*********************************************************
-.TP
-.B \-\-tls-remote name
-Accept connections only from a host with X509 name
-or common name equal to
-.B name.
-The remote host must also pass all other tests
-of verification.
-
-.B NOTE:
-Because tls-remote may test against a common name prefix,
-only use this option when you are using OpenVPN with a custom CA
-certificate that is under your control.
-Never use this option when your client certificates are signed by
-a third party, such as a commercial web CA.
-
-Name can also be a common name prefix, for example if you
-want a client to only accept connections to "Server-1",
-"Server-2", etc., you can simply use
-.B \-\-tls-remote Server
-
-Using a common name prefix is a useful alternative to managing
-a CRL (Certificate Revocation List) on the client, since it allows the client
-to refuse all certificates except for those associated
-with designated servers.
-
-.B \-\-tls-remote
-is a useful replacement for the
-.B \-\-tls-verify
-option to verify the remote host, because
-.B \-\-tls-remote
-works in a
-.B \-\-chroot
-environment too.
-.\"*********************************************************
-.TP
-.B \-\-ns-cert-type client|server
-Require that peer certificate was signed with an explicit
-.B nsCertType
-designation of "client" or "server".
-
-This is a useful security option for clients, to ensure that
-the host they connect with is a designated server.
-
-See the easy-rsa/build-key-server script for an example
-of how to generate a certificate with the
-.B nsCertType
-field set to "server".
-
-If the server certificate's nsCertType field is set
-to "server", then the clients can verify this with
-.B \-\-ns-cert-type server.
-
-This is an important security precaution to protect against
-a man-in-the-middle attack where an authorized client
-attempts to connect to another client by impersonating the server.
-The attack is easily prevented by having clients verify
-the server certificate using any one of
-.B \-\-ns-cert-type, \-\-tls-remote,
-or
-.B \-\-tls-verify.
-.\"*********************************************************
-.TP
-.B \-\-remote-cert-ku v...
-Require that peer certificate was signed with an explicit
-.B key usage.
-
-This is a useful security option for clients, to ensure that
-the host they connect to is a designated server.
-
-The key usage should be encoded in hex, more than one key
-usage can be specified.
-.\"*********************************************************
-.TP
-.B \-\-remote-cert-eku oid
-Require that peer certificate was signed with an explicit
-.B extended key usage.
-
-This is a useful security option for clients, to ensure that
-the host they connect to is a designated server.
-
-The extended key usage should be encoded in oid notation, or
-OpenSSL symbolic representation.
-.\"*********************************************************
-.TP
-.B \-\-remote-cert-tls client|server
-Require that peer certificate was signed with an explicit
-.B key usage
-and
-.B extended key usage
-based on RFC3280 TLS rules.
-
-This is a useful security option for clients, to ensure that
-the host they connect to is a designated server.
-
-The
-.B \-\-remote-cert-tls client
-option is equivalent to
-.B
-\-\-remote-cert-ku 80 08 88 \-\-remote-cert-eku "TLS Web Client Authentication"
-
-The key usage is digitalSignature and/or keyAgreement.
-
-The
-.B \-\-remote-cert-tls server
-option is equivalent to
-.B
-\-\-remote-cert-ku a0 88 \-\-remote-cert-eku "TLS Web Server Authentication"
-
-The key usage is digitalSignature and ( keyEncipherment or keyAgreement ).
-
-This is an important security precaution to protect against
-a man-in-the-middle attack where an authorized client
-attempts to connect to another client by impersonating the server.
-The attack is easily prevented by having clients verify
-the server certificate using any one of
-.B \-\-remote-cert-tls, \-\-tls-remote,
-or
-.B \-\-tls-verify.
-.\"*********************************************************
-.TP
-.B \-\-crl-verify crl
-Check peer certificate against the file
-.B crl
-in PEM format.
-
-A CRL (certificate revocation list) is used when a particular key is
-compromised but when the overall PKI is still intact.
-
-Suppose you had a PKI consisting of a CA, root certificate, and a number of
-client certificates.  Suppose a laptop computer containing a client key and
-certificate was stolen.  By adding the stolen certificate to the CRL file,
-you could reject any connection which attempts to use it, while preserving the
-overall integrity of the PKI.
-
-The only time when it would be necessary to rebuild the entire PKI from scratch would be
-if the root certificate key itself was compromised.
-.\"*********************************************************
-.SS SSL Library information:
-.\"*********************************************************
-.TP
-.B \-\-show-ciphers
-(Standalone)
-Show all cipher algorithms to use with the
-.B \-\-cipher
-option.
-.\"*********************************************************
-.TP
-.B \-\-show-digests
-(Standalone)
-Show all message digest algorithms to use with the
-.B \-\-auth
-option.
-.\"*********************************************************
-.TP
-.B \-\-show-tls
-(Standalone)
-Show all TLS ciphers (TLS used only as a control channel).  The TLS
-ciphers will be sorted from highest preference (most secure) to
-lowest.
-.\"*********************************************************
-.TP
-.B \-\-show-engines
-(Standalone)
-Show currently available hardware-based crypto acceleration
-engines supported by the OpenSSL library.
-.\"*********************************************************
-.SS Generate a random key:
-Used only for non-TLS static key encryption mode.
-.\"*********************************************************
-.TP
-.B \-\-genkey
-(Standalone)
-Generate a random key to be used as a shared secret,
-for use with the
-.B \-\-secret
-option.  This file must be shared with the
-peer over a pre-existing secure channel such as
-.BR scp (1)
-.
-.\"*********************************************************
-.TP
-.B \-\-secret file
-Write key to
-.B file.
-.\"*********************************************************
-.SS TUN/TAP persistent tunnel config mode:
-Available with linux 2.4.7+.  These options comprise a standalone mode
-of OpenVPN which can be used to create and delete persistent tunnels.
-.\"*********************************************************
-.TP
-.B \-\-mktun
-(Standalone)
-Create a persistent tunnel on platforms which support them such
-as Linux.  Normally TUN/TAP tunnels exist only for
-the period of time that an application has them open.  This option
-takes advantage of the TUN/TAP driver's ability to build persistent
-tunnels that live through multiple instantiations of OpenVPN and die
-only when they are deleted or the machine is rebooted.
-
-One of the advantages of persistent tunnels is that they eliminate the
-need for separate
-.B \-\-up
-and
-.B \-\-down
-scripts to run the appropriate
-.BR ifconfig (8)
-and
-.BR route (8)
-commands.  These commands can be placed in the the same shell script
-which starts or terminates an OpenVPN session.
-
-Another advantage is that open connections through the TUN/TAP-based tunnel
-will not be reset if the OpenVPN peer restarts.  This can be useful to
-provide uninterrupted connectivity through the tunnel in the event of a DHCP
-reset of the peer's public IP address (see the
-.B \-\-ipchange
-option above).
-
-One disadvantage of persistent tunnels is that it is harder to automatically
-configure their MTU value (see
-.B \-\-link-mtu
-and
-.B \-\-tun-mtu
-above).
-
-On some platforms such as Windows, TAP-Win32 tunnels are persistent by
-default.
-.\"*********************************************************
-.TP
-.B \-\-rmtun
-(Standalone)
-Remove a persistent tunnel.
-.\"*********************************************************
-.TP
-.B \-\-dev tunX | tapX
-TUN/TAP device
-.\"*********************************************************
-.TP
-.B \-\-user user
-Optional user to be owner of this tunnel.
-.\"*********************************************************
-.TP
-.B \-\-group group
-Optional group to be owner of this tunnel.
-.\"*********************************************************
-.SS Windows-Specific Options:
-.\"*********************************************************
-.TP
-.B \-\-win-sys path|'env'
-Set the Windows system directory pathname to use when looking for system
-executables such as
-.B route.exe
-and
-.B netsh.exe.
-By default, if this directive is
-not specified, the pathname will be set to "C:\\WINDOWS"
-
-The special string
-.B 'env'
-indicates that the pathname should be read from the
-.B SystemRoot
-environmental variable.
-.\"*********************************************************
-.TP
-.B \-\-ip-win32 method
-When using
-.B \-\-ifconfig
-on Windows, set the TAP-Win32 adapter
-IP address and netmask using
-.B method.
-Don't use this option unless you are also using
-.B \-\-ifconfig.
-
-.B manual \-\-
-Don't set the IP address or netmask automatically.
-Instead output a message
-to the console telling the user to configure the
-adapter manually and indicating the IP/netmask which
-OpenVPN expects the adapter to be set to.
-
-.B dynamic [offset] [lease-time] \-\-
-Automatically set the IP address and netmask by replying to
-DHCP query messages generated by the kernel.  This mode is
-probably the "cleanest" solution
-for setting the TCP/IP properties since it uses the well-known
-DHCP protocol.  There are, however, two prerequisites for using
-this mode: (1) The TCP/IP properties for the TAP-Win32
-adapter must be set to "Obtain an IP address automatically," and
-(2) OpenVPN needs to claim an IP address in the subnet for use
-as the virtual DHCP server address.  By default in
-.B \-\-dev tap
-mode, OpenVPN will
-take the normally unused first address in the subnet.  For example,
-if your subnet is 192.168.4.0 netmask 255.255.255.0, then
-OpenVPN will take the IP address 192.168.4.0 to use as the
-virtual DHCP server address.  In
-.B \-\-dev tun
-mode, OpenVPN will cause the DHCP server to masquerade as if it were
-coming from the remote endpoint.  The optional offset parameter is
-an integer which is > -256 and < 256 and which defaults to 0.
-If offset is positive, the DHCP server will masquerade as the IP
-address at network address + offset.
-If offset is negative, the DHCP server will masquerade as the IP
-address at broadcast address + offset.  The Windows
-.B ipconfig /all
-command can be used to show what Windows thinks the DHCP server
-address is.  OpenVPN will "claim" this address, so make sure to
-use a free address.  Having said that, different OpenVPN instantiations,
-including different ends of the same connection, can share the same
-virtual DHCP server address.  The
-.B lease-time
-parameter controls the lease time of the DHCP assignment given to
-the TAP-Win32 adapter, and is denoted in seconds.
-Normally a very long lease time is preferred
-because it prevents routes involving the TAP-Win32 adapter from
-being lost when the system goes to sleep.  The default
-lease time is one year.
-
-.B netsh \-\-
-Automatically set the IP address and netmask using
-the Windows command-line "netsh"
-command.  This method appears to work correctly on
-Windows XP but not Windows 2000.
-
-.B ipapi \-\-
-Automatically set the IP address and netmask using the
-Windows IP Helper API.  This approach
-does not have ideal semantics, though testing has indicated
-that it works okay in practice.  If you use this option,
-it is best to leave the TCP/IP properties for the TAP-Win32
-adapter in their default state, i.e. "Obtain an IP address
-automatically."
-
-.B adaptive \-\-
-(Default) Try
-.B dynamic
-method initially and fail over to
-.B netsh
-if the DHCP negotiation with the TAP-Win32 adapter does
-not succeed in 20 seconds.  Such failures have been known
-to occur when certain third-party firewall packages installed
-on the client machine block the DHCP negotiation used by
-the TAP-Win32 adapter.
-Note that if the
-.B netsh
-failover occurs, the TAP-Win32 adapter
-TCP/IP properties will be reset from DHCP to static, and this
-will cause future OpenVPN startups using the
-.B adaptive
-mode to use
-.B netsh
-immediately, rather than trying
-.B dynamic
-first.  To "unstick" the
-.B adaptive
-mode from using
-.B netsh,
-run OpenVPN at least once using the
-.B dynamic
-mode to restore the TAP-Win32 adapter TCP/IP properties
-to a DHCP configuration.
-.\"*********************************************************
-.TP
-.B \-\-route-method m
-Which method
-.B m
-to use for adding routes on Windows?
-
-.B adaptive
-(default) \-\- Try IP helper API first.  If that fails, fall
-back to the route.exe shell command.
-.br
-.B ipapi
-\-\- Use IP helper API.
-.br
-.B exe
-\-\- Call the route.exe shell command.
-.\"*********************************************************
-.TP
-.B \-\-dhcp-option type [parm]
-Set extended TAP-Win32 TCP/IP properties, must
-be used with
-.B \-\-ip-win32 dynamic
-or
-.B \-\-ip-win32 adaptive.
-This option can be used to set additional TCP/IP properties
-on the TAP-Win32 adapter, and is particularly useful for
-configuring an OpenVPN client to access a Samba server
-across the VPN.
-
-.B DOMAIN name \-\-
-Set Connection-specific DNS Suffix.
-
-.B DNS addr \-\-
-Set primary domain name server address.  Repeat
-this option to set secondary DNS server addresses.
-
-.B WINS addr \-\-
-Set primary WINS server address (NetBIOS over TCP/IP Name Server).
-Repeat this option to set secondary WINS server addresses.
-
-.B NBDD addr \-\-
-Set primary NBDD server address (NetBIOS over TCP/IP Datagram Distribution Server)
-Repeat this option
-to set secondary NBDD server addresses.
-
-.B NTP addr \-\-
-Set primary NTP server address (Network Time Protocol).
-Repeat this option
-to set secondary NTP server addresses.
-
-.B NBT type \-\-
-Set NetBIOS over TCP/IP Node type.  Possible options:
-.B 1
-= b-node (broadcasts),
-.B 2
-= p-node (point-to-point
-name queries to a WINS server),
-.B 4
-= m-node (broadcast
-then query name server), and
-.B 8
-= h-node (query name server, then broadcast).
-
-.B NBS scope-id \-\-
-Set NetBIOS over TCP/IP Scope. A NetBIOS Scope ID provides an extended
-naming service for the NetBIOS over TCP/IP (Known as NBT) module. The
-primary purpose of a NetBIOS scope ID is to isolate NetBIOS traffic on
-a single network to only those nodes with the same NetBIOS scope ID.
-The NetBIOS scope ID is a character string that is appended to the NetBIOS
-name. The NetBIOS scope ID on two hosts must match, or the two hosts
-will not be able to communicate. The NetBIOS Scope ID also allows
-computers to use the same computer name, as they have different
-scope IDs. The Scope ID becomes a part of the NetBIOS name, making the name unique.
-(This description of NetBIOS scopes courtesy of NeonSurge@abyss.com)
-
-.B DISABLE-NBT \-\-
-Disable Netbios-over-TCP/IP.
-
-Note that if
-.B \-\-dhcp-option
-is pushed via
-.B \-\-push
-to a non-windows client, the option will be saved in the client's
-environment before the up script is called, under
-the name "foreign_option_{n}".
-.\"*********************************************************
-.TP
-.B \-\-tap-sleep n
-Cause OpenVPN to sleep for
-.B n
-seconds immediately after the TAP-Win32 adapter state
-is set to "connected".
-
-This option is intended to be used to troubleshoot problems
-with the
-.B \-\-ifconfig
-and
-.B \-\-ip-win32
-options, and is used to give
-the TAP-Win32 adapter time to come up before
-Windows IP Helper API operations are applied to it.
-.\"*********************************************************
-.TP
-.B \-\-show-net-up
-Output OpenVPN's view of the system routing table and network
-adapter list to the syslog or log file after the TUN/TAP adapter
-has been brought up and any routes have been added.
-.\"*********************************************************
-.TP
-.B \-\-dhcp-renew
-Ask Windows to renew the TAP adapter lease on startup.
-This option is normally unnecessary, as Windows automatically
-triggers a DHCP renegotiation on the TAP adapter when it
-comes up, however if you set the TAP-Win32 adapter
-Media Status property to "Always Connected", you may need this
-flag.
-.\"*********************************************************
-.TP
-.B \-\-dhcp-release
-Ask Windows to release the TAP adapter lease on shutdown.
-This option has the same caveats as
-.B \-\-dhcp-renew
-above.
-.\"*********************************************************
-.TP
-.B \-\-register-dns
-Run net stop dnscache, net start dnscache, ipconfig /flushdns
-and ipconfig /registerdns on connection initiation.
-This is known to kick Windows into
-recognizing pushed DNS servers.
-.\"*********************************************************
-.TP
-.B \-\-pause-exit
-Put up a "press any key to continue" message on the console prior
-to OpenVPN program exit.  This option is automatically used by the
-Windows explorer when OpenVPN is run on a configuration
-file using the right-click explorer menu.
-.\"*********************************************************
-.TP
-.B \-\-service exit-event [0|1]
-Should be used when OpenVPN is being automatically executed by another
-program in such
-a context that no interaction with the user via display or keyboard
-is possible.  In general, end-users should never need to explicitly
-use this option, as it is automatically added by the OpenVPN service wrapper
-when a given OpenVPN configuration is being run as a service.
-
-.B exit-event
-is the name of a Windows global event object, and OpenVPN will continuously
-monitor the state of this event object and exit when it becomes signaled.
-
-The second parameter indicates the initial state of
-.B exit-event
-and normally defaults to 0.
-
-Multiple OpenVPN processes can be simultaneously executed with the same
-.B exit-event
-parameter.  In any case, the controlling process can signal
-.B exit-event,
-causing all such OpenVPN processes to exit.
-
-When executing an OpenVPN process using the
-.B \-\-service
-directive, OpenVPN will probably not have a console
-window to output status/error
-messages, therefore it is useful to use
-.B \-\-log
-or
-.B \-\-log-append
-to write these messages to a file.
-.\"*********************************************************
-.TP
-.B \-\-show-adapters
-(Standalone)
-Show available TAP-Win32 adapters which can be selected using the
-.B \-\-dev-node
-option.  On non-Windows systems, the
-.BR ifconfig (8)
-command provides similar functionality.
-.\"*********************************************************
-.TP
-.B \-\-allow-nonadmin [TAP-adapter]
-(Standalone)
-Set
-.B TAP-adapter
-to allow access from non-administrative accounts.  If
-.B TAP-adapter
-is omitted, all TAP adapters on the system will be configured to allow
-non-admin access.
-The non-admin access setting will only persist for the length of time that
-the TAP-Win32 device object and driver remain loaded, and will need
-to be re-enabled after a reboot, or if the driver is unloaded
-and reloaded.
-This directive can only be used by an administrator.
-.\"*********************************************************
-.TP
-.B \-\-show-valid-subnets
-(Standalone)
-Show valid subnets for
-.B \-\-dev tun
-emulation.  Since the TAP-Win32 driver
-exports an ethernet interface to Windows, and since TUN devices are
-point-to-point in nature, it is necessary for the TAP-Win32 driver
-to impose certain constraints on TUN endpoint address selection.
-
-Namely, the point-to-point endpoints used in TUN device emulation
-must be the middle two addresses of a /30 subnet (netmask 255.255.255.252).
-.\"*********************************************************
-.TP
-.B \-\-show-net
-(Standalone)
-Show OpenVPN's view of the system routing table and network
-adapter list.
-.\"*********************************************************
-.SS PKCS#11 Standalone Options:
-.\"*********************************************************
-.TP
-.B \-\-show-pkcs11-ids provider [cert_private]
-(Standalone)
-Show PKCS#11 token object list. Specify cert_private as 1
-if certificates are stored as private objects.
-
-.B \-\-verb
-option can be used BEFORE this option to produce debugging information.
-.\"*********************************************************
-.SH SCRIPTING AND ENVIRONMENTAL VARIABLES
-OpenVPN exports a series
-of environmental variables for use by user-defined scripts.
-.\"*********************************************************
-.SS Script Order of Execution
-.\"*********************************************************
-.TP
-.B \-\-up
-Executed after TCP/UDP socket bind and TUN/TAP open.
-.\"*********************************************************
-.TP
-.B \-\-tls-verify
-Executed when we have a still untrusted remote peer.
-.\"*********************************************************
-.TP
-.B \-\-ipchange
-Executed after connection authentication, or remote IP address change.
-.\"*********************************************************
-.TP
-.B \-\-client-connect
-Executed in
-.B \-\-mode server
-mode immediately after client authentication.
-.\"*********************************************************
-.TP
-.B \-\-route-up
-Executed after connection authentication, either
-immediately after, or some number of seconds after
-as defined by the
-.B \-\-route-delay
-option.
-.\"*********************************************************
-.TP
-.B \-\-client-disconnect
-Executed in
-.B \-\-mode server
-mode on client instance shutdown.
-.\"*********************************************************
-.TP
-.B \-\-down
-Executed after TCP/UDP and TUN/TAP close.
-.\"*********************************************************
-.TP
-.B \-\-learn-address
-Executed in
-.B \-\-mode server
-mode whenever an IPv4 address/route or MAC address is added to OpenVPN's
-internal routing table.
-.\"*********************************************************
-.TP
-.B \-\-auth-user-pass-verify
-Executed in
-.B \-\-mode server
-mode on new client connections, when the client is
-still untrusted.
-.\"*********************************************************
-.SS String Types and Remapping
-In certain cases, OpenVPN will perform remapping of characters
-in strings.  Essentially, any characters outside the set of
-permitted characters for each string type will be converted
-to underbar ('_').
-
-.B Q:
-Why is string remapping necessary?
-
-.B A:
-It's an important security feature to prevent the malicious coding of
-strings from untrusted sources to be passed as parameters to scripts,
-saved in the environment, used as a common name, translated to a filename,
-etc.
-
-.B Q:
-Can string remapping be disabled?
-
-.B A:
-Yes, by using the
-.B \-\-no-name-remapping
-option, however this should be considered an advanced option.
-
-Here is a brief rundown of OpenVPN's current string types and the 
-permitted character class for each string:
-
-.B X509 Names:
-Alphanumeric, underbar ('_'), dash ('-'), dot ('.'), at 
-('@'), colon (':'), slash ('/'), and equal ('=').  Alphanumeric is defined 
-as a character which will cause the C library isalnum() function to return 
-true.
-
-.B Common Names:
-Alphanumeric, underbar ('_'), dash ('-'), dot ('.'), and at                
-('@').
-
-.B \-\-auth-user-pass username:
-Same as Common Name, with one exception: starting with OpenVPN 2.0.1,
-the username is passed to the OPENVPN_PLUGIN_AUTH_USER_PASS_VERIFY plugin in its raw form,
-without string remapping.
-
-.B \-\-auth-user-pass password:
-Any "printable" character except CR or LF.  
-Printable is defined to be a character which will cause the C library 
-isprint() function to return true.
-
-.B \-\-client-config-dir filename as derived from common name or username:
-Alphanumeric, underbar ('_'), dash ('-'), and dot ('.') except for "." or 
-".." as standalone strings.  As of 2.0.1-rc6, the at ('@') character has
-been added as well for compatibility with the common name character class.
-
-.B Environmental variable names:
-Alphanumeric or underbar ('_').
-
-.B Environmental variable values:
-Any printable character.
-
-For all cases, characters in a string which are not members of the legal 
-character class for that string type will be remapped to underbar ('_').
-.\"*********************************************************
-.SS Environmental Variables
-Once set, a variable is persisted
-indefinitely until it is reset by a new value or a restart,
-
-As of OpenVPN 2.0-beta12, in server mode, environmental
-variables set by OpenVPN
-are scoped according to the client objects
-they are
-associated with, so there should not be any issues with
-scripts having access to stale, previously set variables
-which refer to different client instances.
-.\"*********************************************************
-.TP
-.B bytes_received
-Total number of bytes received from client during VPN session.
-Set prior to execution of the
-.B \-\-client-disconnect
-script.
-.\"*********************************************************
-.TP
-.B bytes_sent
-Total number of bytes sent to client during VPN session.
-Set prior to execution of the
-.B \-\-client-disconnect
-script.
-.\"*********************************************************
-.TP
-.B common_name
-The X509 common name of an authenticated client.
-Set prior to execution of
-.B \-\-client-connect, \-\-client-disconnect,
-and
-.B \-\-auth-user-pass-verify
-scripts.
-.\"*********************************************************
-.TP
-.B config
-Name of first
-.B \-\-config
-file.
-Set on program initiation and reset on SIGHUP.
-.\"*********************************************************
-.TP
-.B daemon
-Set to "1" if the
-.B \-\-daemon
-directive is specified, or "0" otherwise.
-Set on program initiation and reset on SIGHUP.
-.\"*********************************************************
-.TP
-.B daemon_log_redirect
-Set to "1" if the
-.B \-\-log
-or
-.B \-\-log-append
-directives are specified, or "0" otherwise.
-Set on program initiation and reset on SIGHUP.
-.\"*********************************************************
-.TP
-.B dev
-The actual name of the TUN/TAP device, including
-a unit number if it exists.
-Set prior to
-.B \-\-up
-or
-.B \-\-down
-script execution.
-.\"*********************************************************
-.TP
-.B foreign_option_{n}
-An option pushed via
-.B \-\-push
-to a client which does not natively support it,
-such as
-.B \-\-dhcp-option
-on a non-Windows system, will be recorded to this
-environmental variable sequence prior to
-.B \-\-up
-script execution.
-.\"*********************************************************
-.TP
-.B ifconfig_broadcast
-The broadcast address for the virtual
-ethernet segment which is derived from the
-.B \-\-ifconfig
-option when
-.B \-\-dev tap
-is used.
-Set prior to OpenVPN calling the
-.I ifconfig
-or
-.I netsh
-(windows version of ifconfig) commands which
-normally occurs prior to
-.B \-\-up
-script execution.
-.\"*********************************************************
-.TP
-.B ifconfig_local
-The local VPN endpoint IP address specified in the
-.B \-\-ifconfig
-option (first parameter).
-Set prior to OpenVPN calling the
-.I ifconfig
-or
-.I netsh
-(windows version of ifconfig) commands which
-normally occurs prior to
-.B \-\-up
-script execution.
-.\"*********************************************************
-.TP
-.B ifconfig_remote
-The remote VPN endpoint IP address specified in the
-.B \-\-ifconfig
-option (second parameter) when
-.B \-\-dev tun
-is used.
-Set prior to OpenVPN calling the
-.I ifconfig
-or
-.I netsh
-(windows version of ifconfig) commands which
-normally occurs prior to
-.B \-\-up
-script execution.
-.\"*********************************************************
-.TP
-.B ifconfig_netmask
-The subnet mask of the virtual ethernet segment
-that is specified as the second parameter to
-.B \-\-ifconfig
-when
-.B \-\-dev tap
-is being used.
-Set prior to OpenVPN calling the
-.I ifconfig
-or
-.I netsh
-(windows version of ifconfig) commands which
-normally occurs prior to
-.B \-\-up
-script execution.
-.\"*********************************************************
-.TP
-.B ifconfig_pool_local_ip
-The local
-virtual IP address for the TUN/TAP tunnel taken from an
-.B \-\-ifconfig-push
-directive if specified, or otherwise from
-the ifconfig pool (controlled by the
-.B \-\-ifconfig-pool
-config file directive).
-Only set for
-.B \-\-dev tun
-tunnels.
-This option is set on the server prior to execution
-of the
-.B \-\-client-connect
-and
-.B \-\-client-disconnect
-scripts.
-.\"*********************************************************
-.TP
-.B ifconfig_pool_netmask
-The
-virtual IP netmask for the TUN/TAP tunnel taken from an
-.B \-\-ifconfig-push
-directive if specified, or otherwise from
-the ifconfig pool (controlled by the
-.B \-\-ifconfig-pool
-config file directive).
-Only set for
-.B \-\-dev tap
-tunnels.
-This option is set on the server prior to execution
-of the
-.B \-\-client-connect
-and
-.B \-\-client-disconnect
-scripts.
-.\"*********************************************************
-.TP
-.B ifconfig_pool_remote_ip
-The remote
-virtual IP address for the TUN/TAP tunnel taken from an
-.B \-\-ifconfig-push
-directive if specified, or otherwise from
-the ifconfig pool (controlled by the
-.B \-\-ifconfig-pool
-config file directive).
-This option is set on the server prior to execution
-of the
-.B \-\-client-connect
-and
-.B \-\-client-disconnect
-scripts.
-.\"*********************************************************
-.TP
-.B link_mtu
-The maximum packet size (not including the IP header)
-of tunnel data in UDP tunnel transport mode.
-Set prior to
-.B \-\-up
-or
-.B \-\-down
-script execution.
-.\"*********************************************************
-.TP
-.B local
-The
-.B \-\-local
-parameter.
-Set on program initiation and reset on SIGHUP.
-.\"*********************************************************
-.TP
-.B local_port
-The local port number, specified by
-.B \-\-port
-or
-.B \-\-lport.
-Set on program initiation and reset on SIGHUP.
-.\"*********************************************************
-.TP
-.B password
-The password provided by a connecting client.
-Set prior to
-.B \-\-auth-user-pass-verify
-script execution only when the
-.B via-env
-modifier is specified, and deleted from the environment
-after the script returns.
-.\"*********************************************************
-.TP
-.B proto
-The
-.B \-\-proto
-parameter.
-Set on program initiation and reset on SIGHUP.
-.\"*********************************************************
-.TP
-.B remote_{n}
-The
-.B \-\-remote
-parameter.
-Set on program initiation and reset on SIGHUP.
-.\"*********************************************************
-.TP
-.B remote_port_{n}
-The remote port number, specified by
-.B \-\-port
-or
-.B \-\-rport.
-Set on program initiation and reset on SIGHUP.
-.\"*********************************************************
-.TP
-.B route_net_gateway
-The pre-existing default IP gateway in the system routing
-table.
-Set prior to
-.B \-\-up
-script execution.
-.\"*********************************************************
-.TP
-.B route_vpn_gateway
-The default gateway used by
-.B \-\-route
-options, as specified in either the
-.B \-\-route-gateway
-option or the second parameter to
-.B \-\-ifconfig
-when
-.B \-\-dev tun
-is specified.
-Set prior to
-.B \-\-up
-script execution.
-.\"*********************************************************
-.TP
-.B route_{parm}_{n}
-A set of variables which define each route to be added, and
-are set prior to
-.B \-\-up
-script execution.
-
-.B parm
-will be one of "network", "netmask", "gateway", or "metric".
-
-.B n
-is the OpenVPN route number, starting from 1.
-
-If the network or gateway are resolvable DNS names,
-their IP address translations will be recorded rather
-than their names as denoted on the command line
-or configuration file.
-.\"*********************************************************
-.TP
-.B peer_cert
-Temporary file name containing the client certificate upon
-connection.  Useful in conjunction with --tls-verify
-.\"*********************************************************
-.TP
-.B script_context
-Set to "init" or "restart" prior to up/down script execution.
-For more information, see
-documentation for
-.B \-\-up.
-.\"*********************************************************
-.TP
-.B script_type
-Prior to execution of any script, this variable is set to the type of
-script being run.  It can be one of the following:
-.B up, down, ipchange, route-up, tls-verify, auth-user-pass-verify,
-.B client-connect, client-disconnect, 
-or
-.B learn-address.
-.\"*********************************************************
-.TP
-.B signal
-The reason for exit or restart.  Can be one of
-.B sigusr1, sighup, sigterm, sigint, inactive
-(controlled by
-.B \-\-inactive
-option),
-.B ping-exit
-(controlled by
-.B \-\-ping-exit
-option),
-.B ping-restart
-(controlled by
-.B \-\-ping-restart
-option),
-.B connection-reset
-(triggered on TCP connection reset),
-.B error,
-or
-.B unknown
-(unknown signal).  This variable is set just prior to down script execution.
-.\"*********************************************************
-.TP
-.B time_ascii
-Client connection timestamp, formatted as a human-readable
-time string.
-Set prior to execution of the
-.B \-\-client-connect
-script.
-.\"*********************************************************
-.TP
-.B time_duration
-The duration (in seconds) of the client session which is now
-disconnecting.
-Set prior to execution of the
-.B \-\-client-disconnect
-script.
-.\"*********************************************************
-.TP
-.B time_unix
-Client connection timestamp, formatted as a unix integer
-date/time value.
-Set prior to execution of the
-.B \-\-client-connect
-script.
-.\"*********************************************************
-.TP
-.B tls_id_{n}
-A series of certificate fields from the remote peer,
-where
-.B n
-is the verification level.  Only set for TLS connections.  Set prior
-to execution of
-.B \-\-tls-verify
-script.
-.\"*********************************************************
-.TP
-.B tls_serial_{n}
-The serial number of the certificate from the remote peer,
-where
-.B n
-is the verification level.  Only set for TLS connections.  Set prior
-to execution of
-.B \-\-tls-verify
-script. This is in the form of a hex string like "37AB46E0", which is
-suitable for doing serial-based OCSP queries (with OpenSSL, you have
-to prepend "0x" to the string). If something goes wrong while reading
-the value from the certificate it will be an empty string, so your
-code should check that.
-See the contrib/OCSP_check/OCSP_check.sh script for an example.
-.\"*********************************************************
-.TP
-.B tun_mtu
-The MTU of the TUN/TAP device.
-Set prior to
-.B \-\-up
-or
-.B \-\-down
-script execution.
-.\"*********************************************************
-.TP
-.B trusted_ip
-Actual IP address of connecting client or peer which has been authenticated.
-Set prior to execution of
-.B \-\-ipchange, \-\-client-connect,
-and
-.B \-\-client-disconnect
-scripts.
-.\"*********************************************************
-.TP
-.B trusted_port
-Actual port number of connecting client or peer which has been authenticated.
-Set prior to execution of
-.B \-\-ipchange, \-\-client-connect,
-and
-.B \-\-client-disconnect
-scripts.
-.\"*********************************************************
-.TP
-.B untrusted_ip
-Actual IP address of connecting client or peer which has not been authenticated
-yet.  Sometimes used to
-.B nmap
-the connecting host in a
-.B \-\-tls-verify
-script to ensure it is firewalled properly.
-Set prior to execution of
-.B \-\-tls-verify
-and
-.B \-\-auth-user-pass-verify
-scripts.
-.\"*********************************************************
-.TP
-.B untrusted_port
-Actual port number of connecting client or peer which has not been authenticated
-yet.
-Set prior to execution of
-.B \-\-tls-verify
-and
-.B \-\-auth-user-pass-verify
-scripts.
-.\"*********************************************************
-.TP
-.B username
-The username provided by a connecting client.
-Set prior to
-.B \-\-auth-user-pass-verify
-script execution only when the
-.B via-env
-modifier is specified.
-.\"*********************************************************
-.TP
-.B X509_{n}_{subject_field}
-An X509 subject field from the remote peer certificate,
-where
-.B n
-is the verification level.  Only set for TLS connections.  Set prior
-to execution of
-.B \-\-tls-verify
-script.  This variable is similar to
-.B tls_id_{n}
-except the component X509 subject fields are broken out, and
-no string remapping occurs on these field values (except for remapping
-of control characters to "_").
-For example, the following variables would be set on the
-OpenVPN server using the sample client certificate
-in sample-keys (client.crt).
-Note that the verification level is 0 for the client certificate
-and 1 for the CA certificate.
-
-.nf
-.ft 3
-.in +4
-X509_0_emailAddress=me@myhost.mydomain
-X509_0_CN=Test-Client
-X509_0_O=OpenVPN-TEST
-X509_0_ST=NA
-X509_0_C=KG
-X509_1_emailAddress=me@myhost.mydomain
-X509_1_O=OpenVPN-TEST
-X509_1_L=BISHKEK
-X509_1_ST=NA
-X509_1_C=KG
-.in -4
-.ft
-.fi
-.\"*********************************************************
-.SH SIGNALS
-.TP
-.B SIGHUP
-Cause OpenVPN to close all TUN/TAP and
-network connections,
-restart, re-read the configuration file (if any),
-and reopen TUN/TAP and network connections.
-.\"*********************************************************
-.TP
-.B SIGUSR1
-Like 
-.B SIGHUP,
-except don't re-read configuration file, and possibly don't close and reopen TUN/TAP
-device, re-read key files, preserve local IP address/port, or preserve most recently authenticated
-remote IP address/port based on
-.B \-\-persist-tun, \-\-persist-key, \-\-persist-local-ip,
-and
-.B \-\-persist-remote-ip
-options respectively (see above).
-
-This signal may also be internally generated by a timeout condition, governed
-by the
-.B \-\-ping-restart
-option.
-
-This signal, when combined with
-.B \-\-persist-remote-ip,
-may be
-sent when the underlying parameters of the host's network interface change
-such as when the host is a DHCP client and is assigned a new IP address.
-See
-.B \-\-ipchange
-above for more information.
-.\"*********************************************************
-.TP
-.B SIGUSR2
-Causes OpenVPN to display its current statistics (to the syslog
-file if
-.B \-\-daemon
-is used, or stdout otherwise).
-.\"*********************************************************
-.TP
-.B SIGINT, SIGTERM
-Causes OpenVPN to exit gracefully.
-.\"*********************************************************
-.SH TUN/TAP DRIVER SETUP
-If you are running Linux 2.4.7 or higher, you probably have the TUN/TAP driver
-already installed.  If so, there are still a few things you need to do:
-
-Make device:
-.B mknod /dev/net/tun c 10 200
-
-Load driver:
-.B modprobe tun
-.\"*********************************************************
-.SH EXAMPLES
-Prior to running these examples, you should have OpenVPN installed on two
-machines with network connectivity between them.  If you have not
-yet installed OpenVPN, consult the INSTALL file included in the OpenVPN
-distribution.
-.\"*********************************************************
-.SS TUN/TAP Setup:
-If you are using Linux 2.4 or higher,
-make the tun device node and load the tun module:
-.IP
-.B mknod /dev/net/tun c 10 200
-.LP
-.IP
-.B modprobe tun
-.LP
-If you installed from RPM, the
-.B mknod
-step may be omitted, because the RPM install does that for you.
-
-Only Linux 2.4 and newer are supported.
-
-For other platforms, consult the INSTALL file at
-.I http://openvpn.net/install.html
-for more information.
-.\"*********************************************************
-.SS Firewall Setup:
-If firewalls exist between
-the two machines, they should be set to forward UDP port 1194
-in both directions.  If you do not have control over the firewalls
-between the two machines, you may still be able to use OpenVPN by adding
-.B \-\-ping 15
-to each of the
-.B openvpn
-commands used below in the examples (this will cause each peer to send out
-a UDP ping to its remote peer once every 15 seconds which will cause many
-stateful firewalls to forward packets in both directions
-without an explicit firewall rule).
-
-If you are using a Linux iptables-based firewall, you may need to enter
-the following command to allow incoming packets on the TUN device:
-.IP
-.B iptables -A INPUT -i tun+ -j ACCEPT
-.LP
-See the firewalls section below for more information on configuring firewalls
-for use with OpenVPN.
-.\"*********************************************************
-.SS VPN Address Setup:
-For purposes
-of our example, our two machines will be called
-.B may.kg
-and
-.B june.kg.
-If you are constructing a VPN over the internet, then replace
-.B may.kg
-and
-.B june.kg
-with the internet hostname or IP address that each machine will use
-to contact the other over the internet.
-
-Now we will choose the tunnel endpoints.  Tunnel endpoints are
-private IP addresses that only have meaning in the context of
-the VPN.  Each machine will use the tunnel endpoint of the other
-machine to access it over the VPN.  In our example,
-the tunnel endpoint for may.kg
-will be 10.4.0.1 and for june.kg, 10.4.0.2.
-
-Once the VPN is established, you have essentially
-created a secure alternate path between the two hosts
-which is addressed by using the tunnel endpoints.  You can
-control which network
-traffic passes between the hosts 
-(a) over the VPN or (b) independently of the VPN, by choosing whether to use
-(a) the VPN endpoint address or (b) the public internet address,
-to access the remote host. For example if you are on may.kg and you wish to connect to june.kg
-via
-.B ssh
-without using the VPN (since
-.B ssh
-has its own built-in security) you would use the command
-.B ssh june.kg.
-However in the same scenario, you could also use the command
-.B telnet 10.4.0.2
-to create a telnet session with june.kg over the VPN, that would
-use the VPN to secure the session rather than
-.B ssh.
-
-You can use any address you wish for the
-tunnel endpoints
-but make sure that they are private addresses
-(such as those that begin with 10 or 192.168) and that they are
-not part of any existing subnet on the networks of
-either peer, unless you are bridging.  If you use an address that is part of
-your local subnet for either of the tunnel endpoints,
-you will get a weird feedback loop.
-.\"*********************************************************
-.SS Example 1: A simple tunnel without security
-.LP
-On may:
-.IP
-.B openvpn \-\-remote june.kg \-\-dev tun1 \-\-ifconfig 10.4.0.1 10.4.0.2 \-\-verb 9
-.LP
-On june:
-.IP
-.B openvpn \-\-remote may.kg \-\-dev tun1 \-\-ifconfig 10.4.0.2 10.4.0.1 \-\-verb 9
-.LP
-Now verify the tunnel is working by pinging across the tunnel.
-.LP
-On may:
-.IP
-.B ping 10.4.0.2
-.LP
-On june:
-.IP
-.B ping 10.4.0.1
-.LP
-The
-.B \-\-verb 9
-option will produce verbose output, similar to the
-.BR tcpdump (8)
-program.  Omit the
-.B \-\-verb 9
-option to have OpenVPN run quietly.
-.\"*********************************************************
-.SS Example 2: A tunnel with static-key security (i.e. using a pre-shared secret)
-First build a static key on may.
-.IP
-.B openvpn \-\-genkey \-\-secret key
-.LP
-This command will build a random key file called
-.B key
-(in ascii format).
-Now copy
-.B key
-to june over a secure medium such as by
-using the
-.BR scp (1)
-program.
-.LP
-On may:
-.IP
-.B openvpn \-\-remote june.kg \-\-dev tun1 \-\-ifconfig 10.4.0.1 10.4.0.2 \-\-verb 5 \-\-secret key
-.LP
-On june:
-.IP
-.B openvpn \-\-remote may.kg \-\-dev tun1 \-\-ifconfig 10.4.0.2 10.4.0.1 \-\-verb 5 \-\-secret key
-.LP
-Now verify the tunnel is working by pinging across the tunnel.
-.LP
-On may:
-.IP
-.B ping 10.4.0.2
-.LP
-On june:
-.IP
-.B ping 10.4.0.1
-.\"*********************************************************
-.SS Example 3: A tunnel with full TLS-based security
-For this test, we will designate
-.B may
-as the TLS client and
-.B june
-as the TLS server.
-.I Note that client or server designation only has meaning for the TLS subsystem.  It has no bearing on OpenVPN's peer-to-peer, UDP-based communication model.
-
-First, build a separate certificate/key pair
-for both may and june (see above where
-.B \-\-cert
-is discussed for more info).  Then construct
-Diffie Hellman parameters (see above where
-.B \-\-dh
-is discussed for more info).  You can also use the
-included test files client.crt, client.key,
-server.crt, server.key and ca.crt.
-The .crt files are certificates/public-keys, the .key
-files are private keys, and ca.crt is a certification
-authority who has signed both
-client.crt and server.crt.  For Diffie Hellman
-parameters you can use the included file dh1024.pem.
-.I Note that all client, server, and certificate authority certificates and keys included in the OpenVPN distribution are totally insecure and should be used for testing only.
-.LP
-On may:
-.IP
-.B openvpn \-\-remote june.kg \-\-dev tun1 \-\-ifconfig 10.4.0.1 10.4.0.2 \-\-tls-client \-\-ca ca.crt \-\-cert client.crt \-\-key client.key \-\-reneg-sec 60 \-\-verb 5
-.LP
-On june:
-.IP
-.B openvpn \-\-remote may.kg \-\-dev tun1 \-\-ifconfig 10.4.0.2 10.4.0.1 \-\-tls-server \-\-dh dh1024.pem \-\-ca ca.crt \-\-cert server.crt \-\-key server.key \-\-reneg-sec 60 \-\-verb 5
-.LP
-Now verify the tunnel is working by pinging across the tunnel.
-.LP
-On may:
-.IP
-.B ping 10.4.0.2
-.LP
-On june:
-.IP
-.B ping 10.4.0.1
-.LP
-Notice the
-.B \-\-reneg-sec 60
-option we used above.  That tells OpenVPN to renegotiate
-the data channel keys every minute.
-Since we used
-.B \-\-verb 5
-above, you will see status information on each new key negotiation.
-
-For production operations, a key renegotiation interval of 60 seconds
-is probably too frequent.  Omit the
-.B \-\-reneg-sec 60
-option to use OpenVPN's default key renegotiation interval of one hour.
-.\"*********************************************************
-.SS Routing:
-Assuming you can ping across the tunnel,
-the next step is to route a real subnet over
-the secure tunnel.  Suppose that may and june have two network
-interfaces each, one connected
-to the internet, and the other to a private
-network.  Our goal is to securely connect
-both private networks.  We will assume that may's private subnet
-is 10.0.0.0/24 and june's is 10.0.1.0/24.
-.LP
-First, ensure that IP forwarding is enabled on both peers.
-On Linux, enable routing:
-.IP
-.B echo 1 > /proc/sys/net/ipv4/ip_forward
-.LP
-and enable TUN packet forwarding through the firewall:
-.IP
-.B iptables -A FORWARD -i tun+ -j ACCEPT
-.LP
-On may:
-.IP
-.B route add -net 10.0.1.0 netmask 255.255.255.0 gw 10.4.0.2
-.LP
-On june:
-.IP
-.B route add -net 10.0.0.0 netmask 255.255.255.0 gw 10.4.0.1
-.LP
-Now any machine on the 10.0.0.0/24 subnet can
-access any machine on the 10.0.1.0/24 subnet
-over the secure tunnel (or vice versa).
-
-In a production environment, you could put the route command(s)
-in a shell script and execute with the
-.B \-\-up
-option.
-.\"*********************************************************
-.SH FIREWALLS
-OpenVPN's usage of a single UDP port makes it fairly firewall-friendly.
-You should add an entry to your firewall rules to allow incoming OpenVPN
-packets.  On Linux 2.4+:
-.IP
-.B iptables -A INPUT -p udp -s 1.2.3.4 \-\-dport 1194 -j ACCEPT
-.LP
-This will allow incoming packets on UDP port 1194 (OpenVPN's default UDP port)
-from an OpenVPN peer at 1.2.3.4.
-
-If you are using HMAC-based packet authentication (the default in any of
-OpenVPN's secure modes), having the firewall filter on source
-address can be considered optional, since HMAC packet authentication
-is a much more secure method of verifying the authenticity of
-a packet source.  In that case:
-.IP
-.B iptables -A INPUT -p udp \-\-dport 1194 -j ACCEPT
-.LP
-would be adequate and would not render the host inflexible with
-respect to its peer having a dynamic IP address.
-
-OpenVPN also works well on stateful firewalls.  In some cases, you may
-not need to add any static rules to the firewall list if you are
-using a stateful firewall that knows how to track UDP connections.
-If you specify
-.B \-\-ping n,
-OpenVPN will be guaranteed
-to send a packet to its peer at least once every
-.B n
-seconds.  If
-.B n
-is less than the stateful firewall connection timeout, you can
-maintain an OpenVPN connection indefinitely without explicit
-firewall rules.
-
-You should also add firewall rules to allow incoming IP traffic on
-TUN or TAP devices such as:
-.IP
-.B iptables -A INPUT -i tun+ -j ACCEPT
-.LP
-to allow input packets from tun devices,
-.IP
-.B iptables -A FORWARD -i tun+ -j ACCEPT
-.LP
-to allow input packets from tun devices to be forwarded to
-other hosts on the local network,
-.IP
-.B iptables -A INPUT -i tap+ -j ACCEPT
-.LP
-to allow input packets from tap devices, and
-.IP
-.B iptables -A FORWARD -i tap+ -j ACCEPT
-.LP
-to allow input packets from tap devices to be forwarded to
-other hosts on the local network.
-
-These rules are secure if you use packet authentication,
-since no incoming packets will arrive on a TUN or TAP
-virtual device
-unless they first pass an HMAC authentication test.
-.\"*********************************************************
-.SH FAQ
-.I http://openvpn.net/faq.html
-.\"*********************************************************
-.SH HOWTO
-For a more comprehensive guide to setting up OpenVPN
-in a production setting, see the OpenVPN HOWTO at
-.I http://openvpn.net/howto.html
-.\"*********************************************************
-.SH PROTOCOL
-For a description of OpenVPN's underlying protocol,
-see 
-.I http://openvpn.net/security.html
-.\"*********************************************************
-.SH WEB
-OpenVPN's web site is at
-.I http://openvpn.net/
-
-Go here to download the latest version of OpenVPN, subscribe
-to the mailing lists, read the mailing list
-archives, or browse the SVN repository.
-.\"*********************************************************
-.SH BUGS
-Report all bugs to the OpenVPN team <info@openvpn.net>.
-.\"*********************************************************
-.SH "SEE ALSO"
-.BR dhcpcd (8),
-.BR ifconfig (8),
-.BR openssl (1),
-.BR route (8),
-.BR scp (1)
-.BR ssh (1)
-.\"*********************************************************
-.SH NOTES 
-.LP
-This product includes software developed by the
-OpenSSL Project (
-.I http://www.openssl.org/
-)
-
-For more information on the TLS protocol, see
-.I http://www.ietf.org/rfc/rfc2246.txt
-
-For more information on the LZO real-time compression library see
-.I http://www.oberhumer.com/opensource/lzo/
-.\"*********************************************************
-.SH COPYRIGHT
-Copyright (C) 2002-2010 OpenVPN Technologies, Inc. This program is free software;
-you can redistribute it and/or modify
-it under the terms of the GNU General Public License version 2
-as published by the Free Software Foundation.
-.\"*********************************************************
-.SH AUTHORS
-James Yonan <jim@yonan.net>