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. 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  *      Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
  36  *      - Initial distribution.
  37  * $FreeBSD: src/sys/net/slcompress.h,v 1.14.2.1 2000/05/05 13:37:06 jlemon Exp $
  38  * $DragonFly: src/sys/net/slcompress.h,v 1.5 2006/05/21 03:43:45 dillon Exp $
  39  */
  40
  41 #ifndef _NET_SLCOMPRESS_H_
  42 #define _NET_SLCOMPRESS_H_
  43
  44 #ifndef _SYS_TYPES_H_
  45 #include <sys/types.h>
  46 #endif
  47 #ifndef _NETINET_IP_H_
  48 #include <netinet/ip.h>
  49 #endif
  50
  51 #define MAX_STATES 16           /* must be > 2 and < 256 */
  52 #define MAX_HDR 128
  53
  54 /*
  55  * Compressed packet format:
  56  *
  57  * The first octet contains the packet type (top 3 bits), TCP
  58  * 'push' bit, and flags that indicate which of the 4 TCP sequence
  59  * numbers have changed (bottom 5 bits).  The next octet is a
  60  * conversation number that associates a saved IP/TCP header with
  61  * the compressed packet.  The next two octets are the TCP checksum
  62  * from the original datagram.  The next 0 to 15 octets are
  63  * sequence number changes, one change per bit set in the header
  64  * (there may be no changes and there are two special cases where
  65  * the receiver implicitly knows what changed -- see below).
  66  *
  67  * There are 5 numbers which can change (they are always inserted
  68  * in the following order): TCP urgent pointer, window,
  69  * acknowledgement, sequence number and IP ID.  (The urgent pointer
  70  * is different from the others in that its value is sent, not the
  71  * change in value.)  Since typical use of SLIP links is biased
  72  * toward small packets (see comments on MTU/MSS below), changes
  73  * use a variable length coding with one octet for numbers in the
  74  * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
  75  * range 256 - 65535 or 0.  (If the change in sequence number or
  76  * ack is more than 65535, an uncompressed packet is sent.)
  77  */
  78
  79 /*
  80  * Packet types (must not conflict with IP protocol version)
  81  *
  82  * The top nibble of the first octet is the packet type.  There are
  83  * three possible types: IP (not proto TCP or tcp with one of the
  84  * control flags set); uncompressed TCP (a normal IP/TCP packet but
  85  * with the 8-bit protocol field replaced by an 8-bit connection id --
  86  * this type of packet syncs the sender & receiver); and compressed
  87  * TCP (described above).
  88  *
  89  * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
  90  * is logically part of the 4-bit "changes" field that follows.  Top
  91  * three bits are actual packet type.  For backward compatibility
  92  * and in the interest of conserving bits, numbers are chosen so the
  93  * IP protocol version number (4) which normally appears in this nibble
  94  * means "IP packet".
  95  */
  96
  97 /* packet types */
  98 #define TYPE_IP 0x40
  99 #define TYPE_UNCOMPRESSED_TCP 0x70
 100 #define TYPE_COMPRESSED_TCP 0x80
 101 #define TYPE_ERROR 0x00
 102
 103 /* Bits in first octet of compressed packet */
 104 #define NEW_C   0x40    /* flag bits for what changed in a packet */
 105 #define NEW_I   0x20
 106 #define NEW_S   0x08
 107 #define NEW_A   0x04
 108 #define NEW_W   0x02
 109 #define NEW_U   0x01
 110
 111 /* reserved, special-case values of above */
 112 #define SPECIAL_I (NEW_S|NEW_W|NEW_U)           /* echoed interactive traffic */
 113 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U)     /* unidirectional data */
 114 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
 115
 116 #define TCP_PUSH_BIT 0x10
 117
 118
 119 /*
 120  * "state" data for each active tcp conversation on the wire.  This is
 121  * basically a copy of the entire IP/TCP header from the last packet
 122  * we saw from the conversation together with a small identifier
 123  * the transmit & receive ends of the line use to locate saved header.
 124  */
 125 struct cstate {
 126         struct cstate *cs_next; /* next most recently used cstate (xmit only) */
 127         u_int16_t cs_hlen;      /* size of hdr (receive only) */
 128         u_char cs_id;           /* connection # associated with this state */
 129         u_char cs_filler;
 130         union {
 131                 char csu_hdr[MAX_HDR];
 132                 struct ip csu_ip;       /* ip/tcp hdr from most recent packet */
 133         } slcs_u;
 134 };
 135 #define cs_ip slcs_u.csu_ip
 136 #define cs_hdr slcs_u.csu_hdr
 137
 138 /*
 139  * all the state data for one serial line (we need one of these
 140  * per line).
 141  */
 142 struct slcompress {
 143         struct cstate *last_cs; /* most recently used tstate */
 144         u_char last_recv;       /* last rcvd conn. id */
 145         u_char last_xmit;       /* last sent conn. id */
 146         u_int16_t flags;
 147 #ifndef SL_NO_STATS
 148         int sls_packets;        /* outbound packets */
 149         int sls_compressed;     /* outbound compressed packets */
 150         int sls_searches;       /* searches for connection state */
 151         int sls_misses;         /* times couldn't find conn. state */
 152         int sls_uncompressedin; /* inbound uncompressed packets */
 153         int sls_compressedin;   /* inbound compressed packets */
 154         int sls_errorin;        /* inbound unknown type packets */
 155         int sls_tossed;         /* inbound packets tossed because of error */
 156 #endif
 157         struct cstate tstate[MAX_STATES];       /* xmit connection states */
 158         struct cstate rstate[MAX_STATES];       /* receive connection states */
 159 };
 160 /* flag values */
 161 #define SLF_TOSS 1              /* tossing rcvd frames because of input err */
 162
 163 struct mbuf;
 164
 165 void     sl_compress_init (struct slcompress *, int);
 166 u_int    sl_compress_tcp (struct mbuf *,
 167             struct ip *, struct slcompress *, int);
 168 int      sl_uncompress_tcp (u_char **, int, u_int, struct slcompress *);
 169 int      sl_uncompress_tcp_core (u_char *, int, int, u_int,
 170             struct slcompress *, u_char **, u_int *);
 171
 172 #endif /* !_NET_SLCOMPRESS_H_ */