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