netbsd-1.2/slcompress.h

   1 /*      $NetBSD: slcompress.h,v 1.12 1998/02/09 17:43:56 perry Exp $    */
   2 /*      Id: slcompress.h,v 1.4 1994/09/21 06:50:08 paulus Exp   */
   3
   4 /*
   5  * Copyright (c) 1989, 1993
   6  *      The Regents of the University of California.  All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  *      @(#)slcompress.h        8.1 (Berkeley) 6/10/93
  37  */
  38
  39 /*
  40  * Definitions for tcp compression routines.
  41  *
  42  * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
  43  *      - Initial distribution.
  44  */
  45
  46 #ifndef _NET_SLCOMPRESS_H_
  47 #define _NET_SLCOMPRESS_H_
  48
  49 #define MAX_STATES 16           /* must be > 2 and < 256 */
  50 #define MAX_HDR MLEN            /* XXX 4bsd-ism: should really be 128 */
  51
  52 /*
  53  * Compressed packet format:
  54  *
  55  * The first octet contains the packet type (top 3 bits), TCP
  56  * 'push' bit, and flags that indicate which of the 4 TCP sequence
  57  * numbers have changed (bottom 5 bits).  The next octet is a
  58  * conversation number that associates a saved IP/TCP header with
  59  * the compressed packet.  The next two octets are the TCP checksum
  60  * from the original datagram.  The next 0 to 15 octets are
  61  * sequence number changes, one change per bit set in the header
  62  * (there may be no changes and there are two special cases where
  63  * the receiver implicitly knows what changed -- see below).
  64  *
  65  * There are 5 numbers which can change (they are always inserted
  66  * in the following order): TCP urgent pointer, window,
  67  * acknowlegement, sequence number and IP ID.  (The urgent pointer
  68  * is different from the others in that its value is sent, not the
  69  * change in value.)  Since typical use of SLIP links is biased
  70  * toward small packets (see comments on MTU/MSS below), changes
  71  * use a variable length coding with one octet for numbers in the
  72  * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
  73  * range 256 - 65535 or 0.  (If the change in sequence number or
  74  * ack is more than 65535, an uncompressed packet is sent.)
  75  */
  76
  77 /*
  78  * Packet types (must not conflict with IP protocol version)
  79  *
  80  * The top nibble of the first octet is the packet type.  There are
  81  * three possible types: IP (not proto TCP or tcp with one of the
  82  * control flags set); uncompressed TCP (a normal IP/TCP packet but
  83  * with the 8-bit protocol field replaced by an 8-bit connection id --
  84  * this type of packet syncs the sender & receiver); and compressed
  85  * TCP (described above).
  86  *
  87  * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
  88  * is logically part of the 4-bit "changes" field that follows.  Top
  89  * three bits are actual packet type.  For backward compatibility
  90  * and in the interest of conserving bits, numbers are chosen so the
  91  * IP protocol version number (4) which normally appears in this nibble
  92  * means "IP packet".
  93  */
  94
  95 /* packet types */
  96 #define TYPE_IP 0x40
  97 #define TYPE_UNCOMPRESSED_TCP 0x70
  98 #define TYPE_COMPRESSED_TCP 0x80
  99 #define TYPE_ERROR 0x00
 100
 101 /* Bits in first octet of compressed packet */
 102 #define NEW_C   0x40    /* flag bits for what changed in a packet */
 103 #define NEW_I   0x20
 104 #define NEW_S   0x08
 105 #define NEW_A   0x04
 106 #define NEW_W   0x02
 107 #define NEW_U   0x01
 108
 109 /* reserved, special-case values of above */
 110 #define SPECIAL_I (NEW_S|NEW_W|NEW_U)           /* echoed interactive traffic */
 111 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U)     /* unidirectional data */
 112 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
 113
 114 #define TCP_PUSH_BIT 0x10
 115
 116
 117 /*
 118  * "state" data for each active tcp conversation on the wire.  This is
 119  * basically a copy of the entire IP/TCP header from the last packet
 120  * we saw from the conversation together with a small identifier
 121  * the transmit & receive ends of the line use to locate saved header.
 122  */
 123 struct cstate {
 124         struct cstate *cs_next; /* next most recently used cstate (xmit only) */
 125         u_int16_t cs_hlen;      /* size of hdr (receive only) */
 126         u_char cs_id;           /* connection # associated with this state */
 127         u_char cs_filler;
 128         union {
 129                 char csu_hdr[MAX_HDR];
 130                 struct ip csu_ip;       /* ip/tcp hdr from most recent packet */
 131         } slcs_u;
 132 };
 133 #define cs_ip slcs_u.csu_ip
 134 #define cs_hdr slcs_u.csu_hdr
 135
 136 /*
 137  * all the state data for one serial line (we need one of these
 138  * per line).
 139  */
 140 struct slcompress {
 141         struct cstate *last_cs; /* most recently used tstate */
 142         u_char last_recv;       /* last rcvd conn. id */
 143         u_char last_xmit;       /* last sent conn. id */
 144         u_int16_t flags;
 145 #ifndef SL_NO_STATS
 146         int sls_packets;        /* outbound packets */
 147         int sls_compressed;     /* outbound compressed packets */
 148         int sls_searches;       /* searches for connection state */
 149         int sls_misses;         /* times couldn't find conn. state */
 150         int sls_uncompressedin; /* inbound uncompressed packets */
 151         int sls_compressedin;   /* inbound compressed packets */
 152         int sls_errorin;        /* inbound unknown type packets */
 153         int sls_tossed;         /* inbound packets tossed because of error */
 154 #endif
 155         struct cstate tstate[MAX_STATES];       /* xmit connection states */
 156         struct cstate rstate[MAX_STATES];       /* receive connection states */
 157 };
 158 /* flag values */
 159 #define SLF_TOSS 1              /* tossing rcvd frames because of input err */
 160
 161 void    sl_compress_init __P((struct slcompress *));
 162 void    sl_compress_setup __P((struct slcompress *, int));
 163 u_int   sl_compress_tcp __P((struct mbuf *,
 164             struct ip *, struct slcompress *, int));
 165 int     sl_uncompress_tcp __P((u_char **, int, u_int, struct slcompress *));
 166 int     sl_uncompress_tcp_core __P((u_char *, int, int, u_int,
 167             struct slcompress *, u_char **, u_int *));
 168
 169 #endif /* _NET_SLCOMPRESS_H_ */