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