sys/net/slcompress.h

   1 /*
   2  * Definitions for tcp compression routines.
   3  *
   4  * Copyright (c) 1989, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  *
  31  *      Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
  32  *      - Initial distribution.
  33  * $FreeBSD: src/sys/net/slcompress.h,v 1.14.2.1 2000/05/05 13:37:06 jlemon Exp $
  34  * $DragonFly: src/sys/net/slcompress.h,v 1.5 2006/05/21 03:43:45 dillon Exp $
  35  */
  36
  37 #ifndef _NET_SLCOMPRESS_H_
  38 #define _NET_SLCOMPRESS_H_
  39
  40 #ifndef _SYS_TYPES_H_
  41 #include <sys/types.h>
  42 #endif
  43 #ifndef _NETINET_IP_H_
  44 #include <netinet/ip.h>
  45 #endif
  46
  47 #define MAX_STATES 16           /* must be > 2 and < 256 */
  48 #define MAX_HDR 128
  49
  50 /*
  51  * Compressed packet format:
  52  *
  53  * The first octet contains the packet type (top 3 bits), TCP
  54  * 'push' bit, and flags that indicate which of the 4 TCP sequence
  55  * numbers have changed (bottom 5 bits).  The next octet is a
  56  * conversation number that associates a saved IP/TCP header with
  57  * the compressed packet.  The next two octets are the TCP checksum
  58  * from the original datagram.  The next 0 to 15 octets are
  59  * sequence number changes, one change per bit set in the header
  60  * (there may be no changes and there are two special cases where
  61  * the receiver implicitly knows what changed -- see below).
  62  *
  63  * There are 5 numbers which can change (they are always inserted
  64  * in the following order): TCP urgent pointer, window,
  65  * acknowledgement, sequence number and IP ID.  (The urgent pointer
  66  * is different from the others in that its value is sent, not the
  67  * change in value.)  Since typical use of SLIP links is biased
  68  * toward small packets (see comments on MTU/MSS below), changes
  69  * use a variable length coding with one octet for numbers in the
  70  * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
  71  * range 256 - 65535 or 0.  (If the change in sequence number or
  72  * ack is more than 65535, an uncompressed packet is sent.)
  73  */
  74
  75 /*
  76  * Packet types (must not conflict with IP protocol version)
  77  *
  78  * The top nibble of the first octet is the packet type.  There are
  79  * three possible types: IP (not proto TCP or tcp with one of the
  80  * control flags set); uncompressed TCP (a normal IP/TCP packet but
  81  * with the 8-bit protocol field replaced by an 8-bit connection id --
  82  * this type of packet syncs the sender & receiver); and compressed
  83  * TCP (described above).
  84  *
  85  * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
  86  * is logically part of the 4-bit "changes" field that follows.  Top
  87  * three bits are actual packet type.  For backward compatibility
  88  * and in the interest of conserving bits, numbers are chosen so the
  89  * IP protocol version number (4) which normally appears in this nibble
  90  * means "IP packet".
  91  */
  92
  93 /* packet types */
  94 #define TYPE_IP 0x40
  95 #define TYPE_UNCOMPRESSED_TCP 0x70
  96 #define TYPE_COMPRESSED_TCP 0x80
  97 #define TYPE_ERROR 0x00
  98
  99 /* Bits in first octet of compressed packet */
 100 #define NEW_C   0x40    /* flag bits for what changed in a packet */
 101 #define NEW_I   0x20
 102 #define NEW_S   0x08
 103 #define NEW_A   0x04
 104 #define NEW_W   0x02
 105 #define NEW_U   0x01
 106
 107 /* reserved, special-case values of above */
 108 #define SPECIAL_I (NEW_S|NEW_W|NEW_U)           /* echoed interactive traffic */
 109 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U)     /* unidirectional data */
 110 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
 111
 112 #define TCP_PUSH_BIT 0x10
 113
 114
 115 /*
 116  * "state" data for each active tcp conversation on the wire.  This is
 117  * basically a copy of the entire IP/TCP header from the last packet
 118  * we saw from the conversation together with a small identifier
 119  * the transmit & receive ends of the line use to locate saved header.
 120  */
 121 struct cstate {
 122         struct cstate *cs_next; /* next most recently used cstate (xmit only) */
 123         u_int16_t cs_hlen;      /* size of hdr (receive only) */
 124         u_char cs_id;           /* connection # associated with this state */
 125         u_char cs_filler;
 126         union {
 127                 char csu_hdr[MAX_HDR];
 128                 struct ip csu_ip;       /* ip/tcp hdr from most recent packet */
 129         } slcs_u;
 130 };
 131 #define cs_ip slcs_u.csu_ip
 132 #define cs_hdr slcs_u.csu_hdr
 133
 134 /*
 135  * all the state data for one serial line (we need one of these
 136  * per line).
 137  */
 138 struct slcompress {
 139         struct cstate *last_cs; /* most recently used tstate */
 140         u_char last_recv;       /* last rcvd conn. id */
 141         u_char last_xmit;       /* last sent conn. id */
 142         u_int16_t flags;
 143 #ifndef SL_NO_STATS
 144         int sls_packets;        /* outbound packets */
 145         int sls_compressed;     /* outbound compressed packets */
 146         int sls_searches;       /* searches for connection state */
 147         int sls_misses;         /* times couldn't find conn. state */
 148         int sls_uncompressedin; /* inbound uncompressed packets */
 149         int sls_compressedin;   /* inbound compressed packets */
 150         int sls_errorin;        /* inbound unknown type packets */
 151         int sls_tossed;         /* inbound packets tossed because of error */
 152 #endif
 153         struct cstate tstate[MAX_STATES];       /* xmit connection states */
 154         struct cstate rstate[MAX_STATES];       /* receive connection states */
 155 };
 156 /* flag values */
 157 #define SLF_TOSS 1              /* tossing rcvd frames because of input err */
 158
 159 struct mbuf;
 160
 161 void     sl_compress_init (struct slcompress *, int);
 162 u_int    sl_compress_tcp (struct mbuf *,
 163             struct ip *, struct slcompress *, int);
 164 int      sl_uncompress_tcp (u_char **, int, u_int, struct slcompress *);
 165 int      sl_uncompress_tcp_core (u_char *, int, int, u_int,
 166             struct slcompress *, u_char **, u_int *);
 167
 168 #endif /* !_NET_SLCOMPRESS_H_ */