slcompress.h revision 1.10
1/* $OpenBSD: slcompress.h,v 1.10 2017/01/24 10:08:30 krw Exp $ */ 2/* $NetBSD: slcompress.h,v 1.11 1997/05/17 21:12:11 christos Exp $ */ 3 4/* 5 * Copyright (c) 1989, 1993 6 * The Regents of the University of California. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)slcompress.h 8.1 (Berkeley) 6/10/93 33 */ 34 35/* 36 * Definitions for tcp compression routines. 37 * 38 * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989: 39 * - Initial distribution. 40 */ 41 42#ifndef _NET_SLCOMPRESS_H_ 43#define _NET_SLCOMPRESS_H_ 44 45#define MAX_STATES 16 /* must be > 2 and < 256 */ 46#define MAX_HDR MLEN /* XXX 4bsd-ism: should really be 128 */ 47 48/* 49 * Compressed packet format: 50 * 51 * The first octet contains the packet type (top 3 bits), TCP 52 * 'push' bit, and flags that indicate which of the 4 TCP sequence 53 * numbers have changed (bottom 5 bits). The next octet is a 54 * conversation number that associates a saved IP/TCP header with 55 * the compressed packet. The next two octets are the TCP checksum 56 * from the original datagram. The next 0 to 15 octets are 57 * sequence number changes, one change per bit set in the header 58 * (there may be no changes and there are two special cases where 59 * the receiver implicitly knows what changed -- see below). 60 * 61 * There are 5 numbers which can change (they are always inserted 62 * in the following order): TCP urgent pointer, window, 63 * acknowledgement, sequence number and IP ID. (The urgent pointer 64 * is different from the others in that its value is sent, not the 65 * change in value.) Since typical use of SLIP links is biased 66 * toward small packets (see comments on MTU/MSS below), changes 67 * use a variable length coding with one octet for numbers in the 68 * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the 69 * range 256 - 65535 or 0. (If the change in sequence number or 70 * ack is more than 65535, an uncompressed packet is sent.) 71 */ 72 73/* 74 * Packet types (must not conflict with IP protocol version) 75 * 76 * The top nibble of the first octet is the packet type. There are 77 * three possible types: IP (not proto TCP or tcp with one of the 78 * control flags set); uncompressed TCP (a normal IP/TCP packet but 79 * with the 8-bit protocol field replaced by an 8-bit connection id -- 80 * this type of packet syncs the sender & receiver); and compressed 81 * TCP (described above). 82 * 83 * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and 84 * is logically part of the 4-bit "changes" field that follows. Top 85 * three bits are actual packet type. For backward compatibility 86 * and in the interest of conserving bits, numbers are chosen so the 87 * IP protocol version number (4) which normally appears in this nibble 88 * means "IP packet". 89 */ 90 91/* packet types */ 92#define TYPE_IP 0x40 93#define TYPE_UNCOMPRESSED_TCP 0x70 94#define TYPE_COMPRESSED_TCP 0x80 95#define TYPE_ERROR 0x00 96 97/* Bits in first octet of compressed packet */ 98#define NEW_C 0x40 /* flag bits for what changed in a packet */ 99#define NEW_I 0x20 100#define NEW_S 0x08 101#define NEW_A 0x04 102#define NEW_W 0x02 103#define NEW_U 0x01 104 105/* reserved, special-case values of above */ 106#define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */ 107#define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */ 108#define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U) 109 110#define TCP_PUSH_BIT 0x10 111 112#ifdef _KERNEL 113 114/* 115 * "state" data for each active tcp conversation on the wire. This is 116 * basically a copy of the entire IP/TCP header from the last packet 117 * we saw from the conversation together with a small identifier 118 * the transmit & receive ends of the line use to locate saved header. 119 */ 120struct cstate { 121 struct cstate *cs_next; /* next most recently used cstate (xmit only) */ 122 u_int16_t cs_hlen; /* size of hdr (receive only) */ 123 u_char cs_id; /* connection # associated with this state */ 124 u_char cs_filler; 125 union { 126 char csu_hdr[MAX_HDR]; 127 struct ip csu_ip; /* ip/tcp hdr from most recent packet */ 128 } slcs_u; 129}; 130#define cs_ip slcs_u.csu_ip 131#define cs_hdr slcs_u.csu_hdr 132 133/* 134 * all the state data for one serial line (we need one of these 135 * per line). 136 */ 137struct slcompress { 138 struct cstate *last_cs; /* most recently used tstate */ 139 u_char last_recv; /* last rcvd conn. id */ 140 u_char last_xmit; /* last sent conn. id */ 141 u_int16_t flags; 142#ifndef SL_NO_STATS 143 int sls_packets; /* outbound packets */ 144 int sls_compressed; /* outbound compressed packets */ 145 int sls_searches; /* searches for connection state */ 146 int sls_misses; /* times couldn't find conn. state */ 147 int sls_uncompressedin; /* inbound uncompressed packets */ 148 int sls_compressedin; /* inbound compressed packets */ 149 int sls_errorin; /* inbound unknown type packets */ 150 int sls_tossed; /* inbound packets tossed because of error */ 151#endif 152 struct cstate tstate[MAX_STATES]; /* xmit connection states */ 153 struct cstate rstate[MAX_STATES]; /* receive connection states */ 154}; 155/* flag values */ 156#define SLF_TOSS 1 /* tossing rcvd frames because of input err */ 157 158void sl_compress_init(struct slcompress *); 159void sl_compress_setup(struct slcompress *, int); 160u_int sl_compress_tcp(struct mbuf *, 161 struct ip *, struct slcompress *, int); 162int sl_uncompress_tcp(u_char **, int, u_int, struct slcompress *); 163int sl_uncompress_tcp_core(u_char *, int, int, u_int, 164 struct slcompress *, u_char **, u_int *); 165#endif /* _KERNEL */ 166 167#endif /* _NET_SLCOMPRESS_H_ */ 168