netbsd-1.1/slcompress.h

   1 /*      $Id: slcompress.h,v 1.1 1995/12/11 05:17:12 paulus Exp $        */
   2
   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. All advertising materials mentioning features or use of this software
  16  *    must display the following acknowledgement:
  17  *      This product includes software developed by the University of
  18  *      California, Berkeley and its contributors.
  19  * 4. Neither the name of the University nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  *
  35  *      @(#)slcompress.h        8.1 (Berkeley) 6/10/93
  36  */
  37
  38 /*
  39  * Definitions for tcp compression routines.
  40  *
  41  * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
  42  *      - Initial distribution.
  43  */
  44
  45 #define MAX_STATES 16           /* must be > 2 and < 256 */
  46 #define MAX_HDR MLEN            /* XXX 4bsd-ism: should really be 128 */
  47
  48 /*
  49  * Compressed packet format:
  50  *
  51  * The first octet contains the packet type (top 3 bits), TCP
  52  * 'push' bit, and flags that indicate which of the 4 TCP sequence
  53  * numbers have changed (bottom 5 bits).  The next octet is a
  54  * conversation number that associates a saved IP/TCP header with
  55  * the compressed packet.  The next two octets are the TCP checksum
  56  * from the original datagram.  The next 0 to 15 octets are
  57  * sequence number changes, one change per bit set in the header
  58  * (there may be no changes and there are two special cases where
  59  * the receiver implicitly knows what changed -- see below).
  60  *
  61  * There are 5 numbers which can change (they are always inserted
  62  * in the following order): TCP urgent pointer, window,
  63  * acknowlegement, sequence number and IP ID.  (The urgent pointer
  64  * is different from the others in that its value is sent, not the
  65  * change in value.)  Since typical use of SLIP links is biased
  66  * toward small packets (see comments on MTU/MSS below), changes
  67  * use a variable length coding with one octet for numbers in the
  68  * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
  69  * range 256 - 65535 or 0.  (If the change in sequence number or
  70  * ack is more than 65535, an uncompressed packet is sent.)
  71  */
  72
  73 /*
  74  * Packet types (must not conflict with IP protocol version)
  75  *
  76  * The top nibble of the first octet is the packet type.  There are
  77  * three possible types: IP (not proto TCP or tcp with one of the
  78  * control flags set); uncompressed TCP (a normal IP/TCP packet but
  79  * with the 8-bit protocol field replaced by an 8-bit connection id --
  80  * this type of packet syncs the sender & receiver); and compressed
  81  * TCP (described above).
  82  *
  83  * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
  84  * is logically part of the 4-bit "changes" field that follows.  Top
  85  * three bits are actual packet type.  For backward compatibility
  86  * and in the interest of conserving bits, numbers are chosen so the
  87  * IP protocol version number (4) which normally appears in this nibble
  88  * means "IP packet".
  89  */
  90
  91 /* packet types */
  92 #define TYPE_IP 0x40
  93 #define TYPE_UNCOMPRESSED_TCP 0x70
  94 #define TYPE_COMPRESSED_TCP 0x80
  95 #define TYPE_ERROR 0x00
  96
  97 /* Bits in first octet of compressed packet */
  98 #define NEW_C   0x40    /* flag bits for what changed in a packet */
  99 #define NEW_I   0x20
 100 #define NEW_S   0x08
 101 #define NEW_A   0x04
 102 #define NEW_W   0x02
 103 #define NEW_U   0x01
 104
 105 /* reserved, special-case values of above */
 106 #define SPECIAL_I (NEW_S|NEW_W|NEW_U)           /* echoed interactive traffic */
 107 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U)     /* unidirectional data */
 108 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
 109
 110 #define TCP_PUSH_BIT 0x10
 111
 112
 113 /*
 114  * "state" data for each active tcp conversation on the wire.  This is
 115  * basically a copy of the entire IP/TCP header from the last packet
 116  * we saw from the conversation together with a small identifier
 117  * the transmit & receive ends of the line use to locate saved header.
 118  */
 119 struct cstate {
 120         struct cstate *cs_next; /* next most recently used cstate (xmit only) */
 121         u_int16_t cs_hlen;      /* size of hdr (receive only) */
 122         u_char cs_id;           /* connection # associated with this state */
 123         u_char cs_filler;
 124         union {
 125                 char csu_hdr[MAX_HDR];
 126                 struct ip csu_ip;       /* ip/tcp hdr from most recent packet */
 127         } slcs_u;
 128 };
 129 #define cs_ip slcs_u.csu_ip
 130 #define cs_hdr slcs_u.csu_hdr
 131
 132 /*
 133  * all the state data for one serial line (we need one of these
 134  * per line).
 135  */
 136 struct slcompress {
 137         struct cstate *last_cs; /* most recently used tstate */
 138         u_char last_recv;       /* last rcvd conn. id */
 139         u_char last_xmit;       /* last sent conn. id */
 140         u_int16_t flags;
 141 #ifndef SL_NO_STATS
 142         int sls_packets;        /* outbound packets */
 143         int sls_compressed;     /* outbound compressed packets */
 144         int sls_searches;       /* searches for connection state */
 145         int sls_misses;         /* times couldn't find conn. state */
 146         int sls_uncompressedin; /* inbound uncompressed packets */
 147         int sls_compressedin;   /* inbound compressed packets */
 148         int sls_errorin;        /* inbound unknown type packets */
 149         int sls_tossed;         /* inbound packets tossed because of error */
 150 #endif
 151         struct cstate tstate[MAX_STATES];       /* xmit connection states */
 152         struct cstate rstate[MAX_STATES];       /* receive connection states */
 153 };
 154 /* flag values */
 155 #define SLF_TOSS 1              /* tossing rcvd frames because of input err */
 156
 157 void     sl_compress_init __P((struct slcompress *, int));
 158 u_int    sl_compress_tcp __P((struct mbuf *,
 159             struct ip *, struct slcompress *, int));
 160 int      sl_uncompress_tcp __P((u_char **, int, u_int, struct slcompress *));
 161 int      sl_uncompress_tcp_core __P((u_char *, int, int, u_int,
 162             struct slcompress *, u_char **, u_int *));