1 /* slcompress.h 7.4 90/06/28 */ 2 /* 3 * Definitions for tcp compression routines. 4 * 5 * $Header: /cvsroot/src/sys/net/slcompress.h,v 1.3 1993/05/20 03:06:13 cgd Exp $ 6 * 7 * Copyright (c) 1989 Regents of the University of California. 8 * All rights reserved. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989: 39 * - Initial distribution. 40 * 41 * $Id: slcompress.h,v 1.3 1993/05/20 03:06:13 cgd Exp $ 42 */ 43 44 #ifndef _NET_SLCOMPRESS_H_ 45 #define _NET_SLCOMPRESS_H_ 46 47 #define MAX_STATES 16 /* must be > 2 and < 256 */ 48 #define MAX_HDR MLEN /* XXX 4bsd-ism: should really be 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 * acknowlegement, 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_short 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_short 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 extern void sl_compress_init(/* struct slcompress * */); 160 extern u_char sl_compress_tcp(/* struct mbuf *, struct ip *, 161 struct slcompress *, int compress_cid_flag */); 162 extern int sl_uncompress_tcp(/* u_char **, int, u_char, struct slcompress * */); 163 164 #endif /* !_NET_SLCOMPRESS_H_ */ 165