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Diffstat (limited to 'src/openvpn/fragment.h')
| -rw-r--r-- | src/openvpn/fragment.h | 479 |
1 files changed, 479 insertions, 0 deletions
diff --git a/src/openvpn/fragment.h b/src/openvpn/fragment.h new file mode 100644 index 0000000..866573b --- /dev/null +++ b/src/openvpn/fragment.h @@ -0,0 +1,479 @@ +/* + * OpenVPN -- An application to securely tunnel IP networks + * over a single 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 FRAGMENT_H +#define FRAGMENT_H + +/** + * @file + * Data Channel Fragmentation module header file. + */ + + +#ifdef ENABLE_FRAGMENT + +/** + * @addtogroup fragmentation + * @{ + */ + + +#include "common.h" +#include "buffer.h" +#include "interval.h" +#include "mtu.h" +#include "shaper.h" +#include "error.h" + + +#define N_FRAG_BUF 25 + /**< Number of packet buffers for + * reassembling incoming fragmented + * packets. */ + +#define FRAG_TTL_SEC 10 + /**< Time-to-live in seconds for a %fragment. */ + +#define FRAG_WAKEUP_INTERVAL 5 + /**< Interval in seconds between calls to + * wakeup code. */ + +/**************************************************************************/ +/** + * Structure for reassembling one incoming fragmented packet. + */ +struct fragment { + bool defined; /**< Whether reassembly is currently + * taking place in this structure. */ + + int max_frag_size; /**< Maximum size of each %fragment. */ + +# define FRAG_MAP_MASK 0xFFFFFFFF + /**< Mask for reassembly map. */ +# define MAX_FRAGS 32 /**< Maximum number of fragments per packet. */ + unsigned int map; + /**< Reassembly map for recording which + * fragments have been received. + * + * A bit array where each bit + * corresponds to a %fragment. A 1 bit + * in element n means that the %fragment + * n has been received. Needs to have + * at least \c MAX_FRAGS bits. */ + + time_t timestamp; /**< Timestamp for time-to-live purposes. */ + + struct buffer buf; /**< Buffer in which received datagrams + * are reassembled. */ +}; + + +/** + * List of fragment structures for reassembling multiple incoming packets + * concurrently. + */ +struct fragment_list { + int seq_id; /**< Highest fragmentation sequence ID of + * the packets currently being + * reassembled. */ + int index; /**< Index of the packet being reassembled + * with the highest fragmentation + * sequence ID into the \c + * fragment_list.fragments array. */ + +/** Array of reassembly structures, each can contain one whole packet. + * + * The fragmentation sequence IDs of the packets being reassembled in + * this array are linearly increasing. \c + * fragment_list.fragments[fragment_list.index] has an ID of \c + * fragment_list.seq_id. This means that one of these \c fragment_list + * structures can at any one time contain at most packets with the + * fragmentation sequence IDs in the range \c fragment_list.seq_id \c - + * \c N_FRAG_BUF \c + \c 1 to \c fragment_list.seq_id, inclusive. + */ + struct fragment fragments[N_FRAG_BUF]; +}; + + +/** + * Fragmentation and reassembly state for one VPN tunnel instance. + * + * This structure contains all the state necessary for sending and + * receiving fragmented data channel packets associated with one VPN + * tunnel. + * + * The fragmented packet currently being sent to a remote OpenVPN peer is + * stored in \c fragment_master.outgoing. It is copied into that buffer + * by the \c fragment_outgoing() function and the remaining parts to be + * sent can be retrieved by successive calls to \c + * fragment_ready_to_send(). + * + * The received packets currently being reassembled are stored in the \c + * fragment_master.incoming array of \c fragment structures. The \c + * fragment_incoming() function adds newly received parts into this array + * and returns the whole packets once reassembly is complete. + */ +struct fragment_master { + struct event_timeout wakeup; /**< Timeout structure used by the main + * event loop to know when to do + * fragmentation housekeeping. */ + bool received_os_mtu_hint; /**< Whether the operating system has + * explicitly recommended an MTU value. */ +# define N_SEQ_ID 256 + /**< One more than the maximum fragment + * sequence ID, above which the IDs wrap + * to zero. Should be a power of 2. */ + int outgoing_seq_id; /**< Fragment sequence ID of the current + * fragmented packet waiting to be sent. + * + * All parts of a fragmented packet + * share the same sequence ID, so that + * the remote OpenVPN peer can determine + * which parts belong to which original + * packet. */ +# define MAX_FRAG_PKT_SIZE 65536 + /**< (Not used) Maximum packet size before + * fragmenting. */ + int outgoing_frag_size; /**< Size in bytes of each part to be + * sent, except for the last part which + * may be smaller. + * + * This value is computed by the \c + * optimal_fragment_size() function. Its + * value is sent to the remote peer in + * the fragmentation header of the last + * part (i.e. with %fragment type \c + * FRAG_YES_LAST) using the \c + * FRAG_SIZE_MASK and \c FRAG_SIZE_SHIFT + * bits. */ + int outgoing_frag_id; /**< The fragment ID of the next part to + * be sent. Must have a value between 0 + * and \c MAX_FRAGS-1. */ + struct buffer outgoing; /**< Buffer containing the remaining parts + * of the fragmented packet being sent. */ + struct buffer outgoing_return; + /**< Buffer used by \c + * fragment_ready_to_send() to return a + * part to send. */ + + struct fragment_list incoming; + /**< List of structures for reassembling + * incoming packets. */ +}; + + +/**************************************************************************/ +/** @name Fragment header + * @todo Add description of %fragment header format. + *//** @{ *//*************************************/ + +typedef uint32_t fragment_header_type; + /**< Fragmentation information is stored in + * a 32-bit packet header. */ + +#define hton_fragment_header_type(x) htonl(x) + /**< Convert a fragment_header_type from + * host to network order. */ + +#define ntoh_fragment_header_type(x) ntohl(x) + /**< Convert a \c fragment_header_type + * from network to host order. */ + +#define FRAG_TYPE_MASK 0x00000003 + /**< Bit mask for %fragment type info. */ +#define FRAG_TYPE_SHIFT 0 /**< Bit shift for %fragment type info. */ + +#define FRAG_WHOLE 0 /**< Fragment type indicating packet is + * whole. */ +#define FRAG_YES_NOTLAST 1 /**< Fragment type indicating packet is + * part of a fragmented packet, but not + * the last part in the sequence. */ +#define FRAG_YES_LAST 2 /**< Fragment type indicating packet is + * the last part in the sequence of + * parts. */ +#define FRAG_TEST 3 /**< Fragment type not implemented yet. + * In the future might be used as a + * control packet for establishing MTU + * size. */ + +#define FRAG_SEQ_ID_MASK 0x000000ff + /**< Bit mask for %fragment sequence ID. */ +#define FRAG_SEQ_ID_SHIFT 2 /**< Bit shift for %fragment sequence ID. */ + +#define FRAG_ID_MASK 0x0000001f + /**< Bit mask for %fragment ID. */ +#define FRAG_ID_SHIFT 10 + /**< Bit shift for %fragment ID. */ + +/* + * FRAG_SIZE 14 bits + * + * IF FRAG_YES_LAST (FRAG_SIZE): + * The max size of a %fragment. If a %fragment is not the last %fragment in the packet, + * then the %fragment size is guaranteed to be equal to the max %fragment size. Therefore, + * max_frag_size is only sent over the wire if FRAG_LAST is set. Otherwise it is assumed + * to be the actual %fragment size received. + */ +#define FRAG_SIZE_MASK 0x00003fff + /**< Bit mask for %fragment size. */ +#define FRAG_SIZE_SHIFT 15 + /**< Bit shift for %fragment size. */ +#define FRAG_SIZE_ROUND_SHIFT 2 /**< Bit shift for %fragment size rounding. */ +#define FRAG_SIZE_ROUND_MASK ((1 << FRAG_SIZE_ROUND_SHIFT) - 1) + /**< Bit mask for %fragment size rounding. */ + +/* + * FRAG_EXTRA 16 bits + * + * IF FRAG_WHOLE or FRAG_YES_NOTLAST, these 16 bits are available (not currently used) + */ +#define FRAG_EXTRA_MASK 0x0000ffff + /**< Bit mask for extra bits. */ +#define FRAG_EXTRA_SHIFT 15 + /**< Bit shift for extra bits. */ + +/** @} name Fragment header *//********************************************/ + + +/**************************************************************************/ +/** @name Functions for initialization and cleanup *//** @{ *//************/ + +/** + * Allocate and initialize a \c fragment_master structure. + * + * This function also modifies the \a frame packet geometry parameters to + * include space for the fragmentation header. + * + * @param frame - The packet geometry parameters for this VPN + * tunnel, modified by this function to include the + * fragmentation header. + * + * @return A pointer to the new \c fragment_master structure. + */ +struct fragment_master *fragment_init (struct frame *frame); + + +/** + * Allocate internal packet buffers for a \c fragment_master structure. + * + * @param f - The \c fragment_master structure for which to + * allocate the internal buffers. + * @param frame - The packet geometry parameters for this VPN + * tunnel, used to determine how much memory to + * allocate for each packet buffer. + */ +void fragment_frame_init (struct fragment_master *f, const struct frame *frame); + + +/** + * Free a \c fragment_master structure and its internal packet buffers. + * + * @param f - The \c fragment_master structure to free. + */ +void fragment_free (struct fragment_master *f); + +/** @} name Functions for initialization and cleanup *//*******************/ + + +/**************************************************************************/ +/** @name Functions for processing packets received from a remote OpenVPN peer */ +/** @{ */ + +/** + * Process an incoming packet, which may or may not be fragmented. + * + * This function inspects the fragmentation header of the incoming packet + * and processes the packet accordingly. Depending on the %fragment type + * bits (\c FRAG_TYPE_MASK and \c FRAG_TYPE_SHIFT) the packet is processed + * in the following ways: + * - \c FRAG_WHOLE: the packet is not fragmented, and this function does + * not modify its contents, except for removing the fragmentation + * header. + * - \c FRAG_YES_NOTLAST or \c FRAG_YES_LAST: the packet is part of a + * fragmented packet. This function copies the packet into an internal + * reassembly buffer. If the incoming part completes the packet being + * reassembled, the \a buf argument is modified to point to the fully + * reassembled packet. If, on the other hand, reassembly is not yet + * complete, then the the \a buf buffer is set to empty. + * - Any other value: error. + * + * If an error occurs during processing, an error message is logged and + * the length of \a buf is set to zero. + * + * @param f - The \c fragment_master structure for this VPN + * tunnel. + * @param buf - A pointer to the buffer structure containing the + * incoming packet. This pointer will have been + * modified on return either to point to a + * completely reassembled packet, or to have length + * set to zero if reassembly is not yet complete. + * @param frame - The packet geometry parameters for this VPN + * tunnel. + * + * @return Void.\n On return, the \a buf argument will point to a buffer. + * The buffer will have nonzero length if the incoming packet passed + * to this function was whole and unfragmented, or if it was the final + * part of a fragmented packet thereby completing reassembly. On the + * other hand, the buffer will have a length of zero if the incoming + * packet was part of a fragmented packet and reassembly is not yet + * complete. If an error occurs during processing, the buffer length + * is also set to zero. + */ +void fragment_incoming (struct fragment_master *f, struct buffer *buf, + const struct frame* frame); + +/** @} name Functions for processing packets received from a VPN tunnel */ + + +/**************************************************************************/ +/** @name Functions for processing packets to be sent to a remote OpenVPN peer */ +/** @{ */ + +/** + * Process an outgoing packet, which may or may not need to be fragmented. + * + * This function inspects the outgoing packet, determines whether it needs + * to be fragmented, and processes it accordingly. + * + * Depending on the size of the outgoing packet and the packet geometry + * parameters for the VPN tunnel, the packet will or will not be + * fragmented. + * @li Packet size is less than or equal to the maximum packet size for + * this VPN tunnel: fragmentation is not necessary. The \a buf + * argument points to a buffer containing the unmodified outgoing + * packet with a fragmentation header indicating the packet is whole + * (FRAG_WHOLE) prepended. + * @li Packet size is greater than the maximum packet size for this VPN + * tunnel: fragmentation is necessary. The original outgoing packet + * is copied into an internal buffer for fragmentation. The \a buf + * argument is modified to point to the first part of the fragmented + * packet. The remaining parts remain stored in the internal buffer, + * and can be retrieved using the \c fragment_ready_to_send() + * function. + * + * If an error occurs during processing, an error message is logged and + * the length of \a buf is set to zero. + * + * @param f - The \c fragment_master structure for this VPN + * tunnel. + * @param buf - A pointer to the buffer structure containing the + * outgoing packet. This pointer will be modified + * to point to a whole unfragmented packet or to the + * first part of a fragmented packet on return. + * @param frame - The packet geometry parameters for this VPN + * tunnel. + * + * @return Void.\n On return, the \a buf argument will point to a buffer. + * This buffer contains either the whole original outgoing packet if + * fragmentation was not necessary, or the first part of the + * fragmented outgoing packet if fragmentation was necessary. In both + * cases a fragmentation header will have been prepended to inform the + * remote peer how to handle the packet. + */ +void fragment_outgoing (struct fragment_master *f, struct buffer *buf, + const struct frame* frame); + +/** + * Check whether outgoing fragments are ready to be send, and if so make + * one available. + * + * This function checks whether the internal buffer for fragmenting + * outgoing packets contains any unsent parts. If it does not, meaning + * there is nothing waiting to be sent, it returns false. Otherwise there + * are parts ready to be sent, and it returns true. In that case it also + * modifies the \a buf argument to point to a buffer containing the next + * part to be sent. + * + * @param f - The \a fragment_master structure for this VPN + * tunnel. + * @param buf - A pointer to a buffer structure which on return, + * if there are parts waiting to be sent, will point + * to the next part to be sent. + * @param frame - The packet geometry parameters for this VPN + * tunnel. + * + * @return + * @li True, if an outgoing packet has been fragmented and not all parts + * have been sent yet. In this case this function will modify the \a + * buf argument to point to a buffer containing the next part to be + * sent. + * @li False, if there are no outgoing fragmented parts waiting to be + * sent. + */ +bool fragment_ready_to_send (struct fragment_master *f, struct buffer *buf, + const struct frame* frame); + +/** + * Check whether a \c fragment_master structure contains fragments ready + * to be sent. + * + * @param f - The \c fragment_master structure for this VPN + * tunnel. + * + * @return + * @li True, if there are one or more fragments ready to be sent. + * @li False, otherwise. + */ +static inline bool +fragment_outgoing_defined (struct fragment_master *f) +{ + return f->outgoing.len > 0; +} + +/** @} name Functions for processing packets going out through a VPN tunnel */ + + +void fragment_wakeup (struct fragment_master *f, struct frame *frame); + + +/**************************************************************************/ +/** @name Functions for regular housekeeping *//** @{ *//******************/ + +/** + * Perform housekeeping of a \c fragment_master structure. + * + * Housekeeping includes scanning incoming packet reassembly buffers for + * packets which have not yet been reassembled completely but are already + * older than their time-to-live. + * + * @param f - The \c fragment_master structure for this VPN + * tunnel. + * @param frame - The packet geometry parameters for this VPN + * tunnel. + */ +static inline void +fragment_housekeeping (struct fragment_master *f, struct frame *frame, struct timeval *tv) +{ + if (event_timeout_trigger (&f->wakeup, tv, ETT_DEFAULT)) + fragment_wakeup (f, frame); +} + +/** @} name Functions for regular housekeeping *//*************************/ + + +/** @} addtogroup fragmentation *//****************************************/ + + +#endif +#endif |