bsd/net/slcompress.h

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * Definitions for tcp compression routines.
  24  *
  25  * Copyright (c) 1989, 1993
  26  *      The Regents of the University of California.  All rights reserved.
  27  *
  28  * Redistribution and use in source and binary forms, with or without
  29  * modification, are permitted provided that the following conditions
  30  * are met:
  31  * 1. Redistributions of source code must retain the above copyright
  32  *    notice, this list of conditions and the following disclaimer.
  33  * 2. Redistributions in binary form must reproduce the above copyright
  34  *    notice, this list of conditions and the following disclaimer in the
  35  *    documentation and/or other materials provided with the distribution.
  36  * 3. All advertising materials mentioning features or use of this software
  37  *    must display the following acknowledgement:
  38  *      This product includes software developed by the University of
  39  *      California, Berkeley and its contributors.
  40  * 4. Neither the name of the University nor the names of its contributors
  41  *    may be used to endorse or promote products derived from this software
  42  *    without specific prior written permission.
  43  *
  44  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  45  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  46  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  47  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  48  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  49  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  50  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  51  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  52  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  53  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  54  * SUCH DAMAGE.
  55  *
  56  *      Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
  57  *      - Initial distribution.
  58  */
  59
  60 #ifndef _NET_SLCOMPRESS_H_
  61 #define _NET_SLCOMPRESS_H_
  62
  63 #include <netinet/ip.h>
  64
  65 #define MAX_STATES 16           /* must be > 2 and < 256 */
  66 #define MAX_HDR MLEN            /* XXX 4bsd-ism: should really be 128 */
  67
  68 /*
  69  * Compressed packet format:
  70  *
  71  * The first octet contains the packet type (top 3 bits), TCP
  72  * 'push' bit, and flags that indicate which of the 4 TCP sequence
  73  * numbers have changed (bottom 5 bits).  The next octet is a
  74  * conversation number that associates a saved IP/TCP header with
  75  * the compressed packet.  The next two octets are the TCP checksum
  76  * from the original datagram.  The next 0 to 15 octets are
  77  * sequence number changes, one change per bit set in the header
  78  * (there may be no changes and there are two special cases where
  79  * the receiver implicitly knows what changed -- see below).
  80  *
  81  * There are 5 numbers which can change (they are always inserted
  82  * in the following order): TCP urgent pointer, window,
  83  * acknowledgement, sequence number and IP ID.  (The urgent pointer
  84  * is different from the others in that its value is sent, not the
  85  * change in value.)  Since typical use of SLIP links is biased
  86  * toward small packets (see comments on MTU/MSS below), changes
  87  * use a variable length coding with one octet for numbers in the
  88  * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
  89  * range 256 - 65535 or 0.  (If the change in sequence number or
  90  * ack is more than 65535, an uncompressed packet is sent.)
  91  */
  92
  93 /*
  94  * Packet types (must not conflict with IP protocol version)
  95  *
  96  * The top nibble of the first octet is the packet type.  There are
  97  * three possible types: IP (not proto TCP or tcp with one of the
  98  * control flags set); uncompressed TCP (a normal IP/TCP packet but
  99  * with the 8-bit protocol field replaced by an 8-bit connection id --
 100  * this type of packet syncs the sender & receiver); and compressed
 101  * TCP (described above).
 102  *
 103  * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
 104  * is logically part of the 4-bit "changes" field that follows.  Top
 105  * three bits are actual packet type.  For backward compatibility
 106  * and in the interest of conserving bits, numbers are chosen so the
 107  * IP protocol version number (4) which normally appears in this nibble
 108  * means "IP packet".
 109  */
 110
 111 /* packet types */
 112 #define TYPE_IP 0x40
 113 #define TYPE_UNCOMPRESSED_TCP 0x70
 114 #define TYPE_COMPRESSED_TCP 0x80
 115 #define TYPE_ERROR 0x00
 116
 117 /* Bits in first octet of compressed packet */
 118 #define NEW_C   0x40    /* flag bits for what changed in a packet */
 119 #define NEW_I   0x20
 120 #define NEW_S   0x08
 121 #define NEW_A   0x04
 122 #define NEW_W   0x02
 123 #define NEW_U   0x01
 124
 125 /* reserved, special-case values of above */
 126 #define SPECIAL_I (NEW_S|NEW_W|NEW_U)           /* echoed interactive traffic */
 127 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U)     /* unidirectional data */
 128 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
 129
 130 #define TCP_PUSH_BIT 0x10
 131
 132
 133 /*
 134  * "state" data for each active tcp conversation on the wire.  This is
 135  * basically a copy of the entire IP/TCP header from the last packet
 136  * we saw from the conversation together with a small identifier
 137  * the transmit & receive ends of the line use to locate saved header.
 138  */
 139 struct cstate {
 140         struct cstate *cs_next; /* next most recently used cstate (xmit only) */
 141         u_int16_t cs_hlen;      /* size of hdr (receive only) */
 142         u_char cs_id;           /* connection # associated with this state */
 143         u_char cs_filler;
 144         union {
 145                 char csu_hdr[MAX_HDR];
 146                 struct ip csu_ip;       /* ip/tcp hdr from most recent packet */
 147         } slcs_u;
 148 };
 149 #define cs_ip slcs_u.csu_ip
 150 #define cs_hdr slcs_u.csu_hdr
 151
 152 /*
 153  * all the state data for one serial line (we need one of these
 154  * per line).
 155  */
 156 struct slcompress {
 157         struct cstate *last_cs; /* most recently used tstate */
 158         u_char last_recv;       /* last rcvd conn. id */
 159         u_char last_xmit;       /* last sent conn. id */
 160         u_int16_t flags;
 161 #ifndef SL_NO_STATS
 162         int sls_packets;        /* outbound packets */
 163         int sls_compressed;     /* outbound compressed packets */
 164         int sls_searches;       /* searches for connection state */
 165         int sls_misses;         /* times couldn't find conn. state */
 166         int sls_uncompressedin; /* inbound uncompressed packets */
 167         int sls_compressedin;   /* inbound compressed packets */
 168         int sls_errorin;        /* inbound unknown type packets */
 169         int sls_tossed;         /* inbound packets tossed because of error */
 170 #endif
 171         struct cstate tstate[MAX_STATES];       /* xmit connection states */
 172         struct cstate rstate[MAX_STATES];       /* receive connection states */
 173 };
 174 /* flag values */
 175 #define SLF_TOSS 1              /* tossing rcvd frames because of input err */
 176
 177 void     sl_compress_init __P((struct slcompress *, int));
 178 u_int    sl_compress_tcp __P((struct mbuf *,
 179             struct ip *, struct slcompress *, int));
 180 int      sl_uncompress_tcp __P((u_char **, int, u_int, struct slcompress *));
 181 int      sl_uncompress_tcp_core __P((u_char *, int, int, u_int,
 182             struct slcompress *, u_char **, u_int *));
 183
 184 #endif /* !_NET_SLCOMPRESS_H_ */