diff options
Diffstat (limited to 'mtu.h')
| -rw-r--r-- | mtu.h | 304 |
1 files changed, 0 insertions, 304 deletions
@@ -1,304 +0,0 @@ -/* - * 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 - */ - -#ifndef MTU_H -#define MTU_H - -#include "buffer.h" - -/* - * - * Packet maninipulation routes such as encrypt, decrypt, compress, decompress - * are passed a frame buffer that looks like this: - * - * [extra_frame bytes] [mtu bytes] [extra_frame_bytes] [compression overflow bytes] - * ^ - * Pointer passed to function points here so that routine - * can make use of extra_frame bytes before pointer - * to prepend headers, etc. - * - * extra_frame bytes is large enough for all encryption related overhead. - * - * mtu bytes will be the MTU size set in the ifconfig statement that configures - * the TUN or TAP device such as: - * - * ifconfig $1 10.1.0.2 pointopoint 10.1.0.1 mtu 1450 - * - * Compression overflow bytes is the worst-case size expansion that would be - * expected if we tried to compress mtu + extra_frame bytes of uncompressible data. - */ - -/* - * Standard ethernet MTU - */ -#define ETHERNET_MTU 1500 - -/* - * It is a fatal error if mtu is less than - * this value for tun device. - */ -#define TUN_MTU_MIN 100 - -/* - * Default MTU of network over which tunnel data will pass by TCP/UDP. - */ -#define LINK_MTU_DEFAULT 1500 - -/* - * Default MTU of tunnel device. - */ -#define TUN_MTU_DEFAULT 1500 - -/* - * MTU Defaults for TAP devices - */ -#define TAP_MTU_EXTRA_DEFAULT 32 - -/* - * Default MSSFIX value, used for reducing TCP MTU size - */ -#define MSSFIX_DEFAULT 1450 - -/* - * Alignment of payload data such as IP packet or - * ethernet frame. - */ -#define PAYLOAD_ALIGN 4 - -struct frame { - /* - * Maximum datagram size to be sent over the tunnel TCP/UDP channel. - */ - int link_mtu; - int link_mtu_dynamic; - - /* - * How many extra bytes might each subsystem (crypto, TLS, or, compression) - * add to frame in worst case? - * - * mtu + extra_frame = MTU of TCP/UDP transport - */ - int extra_frame; - - /* - * Worst case size added to internal buffer due to functions - * such as compression which can potentially expand the size of uncompressible - * data. - */ - int extra_buffer; - - /* - * Max number of bytes in excess of tun mtu size that we might read - * or write from TUN/TAP device. - */ - int extra_tun; - - /* - * Max number of bytes in excess of link mtu size that we might read - * or write from UDP/TCP link. - */ - int extra_link; - - /* - * Alignment control - */ -# define FRAME_HEADROOM_MARKER_DECRYPT (1<<0) -# define FRAME_HEADROOM_MARKER_FRAGMENT (1<<1) -# define FRAME_HEADROOM_MARKER_READ_LINK (1<<2) -# define FRAME_HEADROOM_MARKER_READ_STREAM (1<<3) - unsigned int align_flags; - int align_adjust; -}; - -/* Routines which read struct frame should use the macros below */ - -/* - * Overhead added to packet payload due to encapsulation - */ -#define EXTRA_FRAME(f) ((f)->extra_frame) - -/* - * Delta between tun payload size and final TCP/UDP datagram size - * (not including extra_link additions) - */ -#define TUN_LINK_DELTA(f) ((f)->extra_frame + (f)->extra_tun) - -/* - * This is the size to "ifconfig" the tun or tap device. - */ -#define TUN_MTU_SIZE(f) ((f)->link_mtu - TUN_LINK_DELTA(f)) -#define TUN_MTU_SIZE_DYNAMIC(f) ((f)->link_mtu_dynamic - TUN_LINK_DELTA(f)) - -/* - * This is the maximum packet size that we need to be able to - * read from or write to a tun or tap device. For example, - * a tap device ifconfiged to an MTU of 1200 might actually want - * to return a packet size of 1214 on a read(). - */ -#define PAYLOAD_SIZE(f) ((f)->link_mtu - (f)->extra_frame) -#define PAYLOAD_SIZE_DYNAMIC(f) ((f)->link_mtu_dynamic - (f)->extra_frame) - -/* - * Max size of a payload packet after encryption, compression, etc. - * overhead is added. - */ -#define EXPANDED_SIZE(f) ((f)->link_mtu) -#define EXPANDED_SIZE_DYNAMIC(f) ((f)->link_mtu_dynamic) -#define EXPANDED_SIZE_MIN(f) (TUN_MTU_MIN + TUN_LINK_DELTA(f)) - -/* - * These values are used as maximum size constraints - * on read() or write() from TUN/TAP device or TCP/UDP port. - */ -#define MAX_RW_SIZE_TUN(f) (PAYLOAD_SIZE(f)) -#define MAX_RW_SIZE_LINK(f) (EXPANDED_SIZE(f) + (f)->extra_link) - -/* - * Control buffer headroom allocations to allow for efficient prepending. - */ -#define FRAME_HEADROOM_BASE(f) (TUN_LINK_DELTA(f) + (f)->extra_buffer + (f)->extra_link) -#define FRAME_HEADROOM(f) frame_headroom(f, 0) -#define FRAME_HEADROOM_ADJ(f, fm) frame_headroom(f, fm) - -/* - * Max size of a buffer used to build a packet for output to - * the TCP/UDP port. - */ -#define BUF_SIZE(f) (TUN_MTU_SIZE(f) + FRAME_HEADROOM_BASE(f) * 2) - -/* - * Function prototypes. - */ - -void frame_finalize (struct frame *frame, - bool link_mtu_defined, - int link_mtu, - bool tun_mtu_defined, - int tun_mtu); - -void frame_subtract_extra (struct frame *frame, const struct frame *src); - -void frame_print (const struct frame *frame, - int level, - const char *prefix); - -void set_mtu_discover_type (int sd, int mtu_type); -int translate_mtu_discover_type_name (const char *name); - -/* - * frame_set_mtu_dynamic and flags - */ - -#define SET_MTU_TUN (1<<0) /* use tun/tap rather than link sizing */ -#define SET_MTU_UPPER_BOUND (1<<1) /* only decrease dynamic MTU */ - -void frame_set_mtu_dynamic (struct frame *frame, int mtu, unsigned int flags); - -/* - * allocate a buffer for socket or tun layer - */ -void alloc_buf_sock_tun (struct buffer *buf, - const struct frame *frame, - const bool tuntap_buffer, - const unsigned int align_mask); - -/* - * EXTENDED_SOCKET_ERROR_CAPABILITY functions -- print extra error info - * on socket errors, such as PMTU size. As of 2003.05.11, only works - * on Linux 2.4+. - */ - -#if EXTENDED_SOCKET_ERROR_CAPABILITY - -void set_sock_extended_error_passing (int sd); -const char *format_extended_socket_error (int fd, int *mtu, struct gc_arena *gc); - -#endif - -/* - * Calculate a starting offset into a buffer object, dealing with - * headroom and alignment issues. - */ -static inline int -frame_headroom (const struct frame *f, const unsigned int flag_mask) -{ - const int offset = FRAME_HEADROOM_BASE (f); - const int adjust = (flag_mask & f->align_flags) ? f->align_adjust : 0; - const int delta = ((PAYLOAD_ALIGN << 24) - (offset + adjust)) & (PAYLOAD_ALIGN - 1); - return offset + delta; -} - -/* - * frame member adjustment functions - */ - -static inline void -frame_add_to_extra_frame (struct frame *frame, const int increment) -{ - frame->extra_frame += increment; -} - -static inline void -frame_add_to_extra_tun (struct frame *frame, const int increment) -{ - frame->extra_tun += increment; -} - -static inline void -frame_add_to_extra_link (struct frame *frame, const int increment) -{ - frame->extra_link += increment; -} - -static inline void -frame_add_to_extra_buffer (struct frame *frame, const int increment) -{ - frame->extra_buffer += increment; -} - -static inline void -frame_add_to_align_adjust (struct frame *frame, const int increment) -{ - frame->align_adjust += increment; -} - -static inline void -frame_align_to_extra_frame (struct frame *frame) -{ - frame->align_adjust = frame->extra_frame + frame->extra_link; -} - -static inline void -frame_or_align_flags (struct frame *frame, const unsigned int flag_mask) -{ - frame->align_flags |= flag_mask; -} - -static inline bool -frame_defined (const struct frame *frame) -{ - return frame->link_mtu > 0; -} - -#endif |