slcompress.h (6538B) - Raw
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 */ 37 38 #ifndef _NET_SLCOMPRESS_H_ 39 #define _NET_SLCOMPRESS_H_ 40 41 #define MAX_STATES 16 /* must be > 2 and < 256 */ 42 #define MAX_HDR 128 43 44 /* 45 * Compressed packet format: 46 * 47 * The first octet contains the packet type (top 3 bits), TCP 48 * 'push' bit, and flags that indicate which of the 4 TCP sequence 49 * numbers have changed (bottom 5 bits). The next octet is a 50 * conversation number that associates a saved IP/TCP header with 51 * the compressed packet. The next two octets are the TCP checksum 52 * from the original datagram. The next 0 to 15 octets are 53 * sequence number changes, one change per bit set in the header 54 * (there may be no changes and there are two special cases where 55 * the receiver implicitly knows what changed -- see below). 56 * 57 * There are 5 numbers which can change (they are always inserted 58 * in the following order): TCP urgent pointer, window, 59 * acknowledgement, sequence number and IP ID. (The urgent pointer 60 * is different from the others in that its value is sent, not the 61 * change in value.) Since typical use of SLIP links is biased 62 * toward small packets (see comments on MTU/MSS below), changes 63 * use a variable length coding with one octet for numbers in the 64 * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the 65 * range 256 - 65535 or 0. (If the change in sequence number or 66 * ack is more than 65535, an uncompressed packet is sent.) 67 */ 68 69 /* 70 * Packet types (must not conflict with IP protocol version) 71 * 72 * The top nibble of the first octet is the packet type. There are 73 * three possible types: IP (not proto TCP or tcp with one of the 74 * control flags set); uncompressed TCP (a normal IP/TCP packet but 75 * with the 8-bit protocol field replaced by an 8-bit connection id -- 76 * this type of packet syncs the sender & receiver); and compressed 77 * TCP (described above). 78 * 79 * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and 80 * is logically part of the 4-bit "changes" field that follows. Top 81 * three bits are actual packet type. For backward compatibility 82 * and in the interest of conserving bits, numbers are chosen so the 83 * IP protocol version number (4) which normally appears in this nibble 84 * means "IP packet". 85 */ 86 87 /* packet types */ 88 #define TYPE_IP 0x40 89 #define TYPE_UNCOMPRESSED_TCP 0x70 90 #define TYPE_COMPRESSED_TCP 0x80 91 #define TYPE_ERROR 0x00 92 93 /* Bits in first octet of compressed packet */ 94 #define NEW_C 0x40 /* flag bits for what changed in a packet */ 95 #define NEW_I 0x20 96 #define NEW_S 0x08 97 #define NEW_A 0x04 98 #define NEW_W 0x02 99 #define NEW_U 0x01 100 101 /* reserved, special-case values of above */ 102 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */ 103 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */ 104 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U) 105 106 #define TCP_PUSH_BIT 0x10 107 108 /* 109 * "state" data for each active tcp conversation on the wire. This is 110 * basically a copy of the entire IP/TCP header from the last packet 111 * we saw from the conversation together with a small identifier 112 * the transmit & receive ends of the line use to locate saved header. 113 */ 114 struct cstate { 115 struct cstate *cs_next; /* next most recently used cstate (xmit only) */ 116 u_int16_t cs_hlen; /* size of hdr (receive only) */ 117 u_char cs_id; /* connection # associated with this state */ 118 u_char cs_filler; 119 union { 120 char csu_hdr[MAX_HDR]; 121 struct ip csu_ip; /* ip/tcp hdr from most recent packet */ 122 } slcs_u; 123 }; 124 #define cs_ip slcs_u.csu_ip 125 #define cs_hdr slcs_u.csu_hdr 126 127 /* 128 * all the state data for one serial line (we need one of these 129 * per line). 130 */ 131 struct slcompress { 132 struct cstate *last_cs; /* most recently used tstate */ 133 u_char last_recv; /* last rcvd conn. id */ 134 u_char last_xmit; /* last sent conn. id */ 135 u_int16_t flags; 136 #ifndef SL_NO_STATS 137 int sls_packets; /* outbound packets */ 138 int sls_compressed; /* outbound compressed packets */ 139 int sls_searches; /* searches for connection state */ 140 int sls_misses; /* times couldn't find conn. state */ 141 int sls_uncompressedin; /* inbound uncompressed packets */ 142 int sls_compressedin; /* inbound compressed packets */ 143 int sls_errorin; /* inbound unknown type packets */ 144 int sls_tossed; /* inbound packets tossed because of error */ 145 #endif 146 struct cstate tstate[MAX_STATES]; /* xmit connection states */ 147 struct cstate rstate[MAX_STATES]; /* receive connection states */ 148 }; 149 /* flag values */ 150 #define SLF_TOSS 1 /* tossing rcvd frames because of input err */ 151 152 void sl_compress_init(struct slcompress *, int); 153 u_int sl_compress_tcp(struct mbuf *, struct ip *, struct slcompress *, int); 154 int sl_uncompress_tcp(u_char **, int, u_int, struct slcompress *); 155 int sl_uncompress_tcp_core(u_char *, int, int, u_int, 156 struct slcompress *, u_char **, u_int *); 157 158 #endif /* !_NET_SLCOMPRESS_H_ */