1 /* $NetBSD: slcompress.h,v 1.20 2020/03/05 07:46:36 riastradh Exp $ */ 2 /* Id: slcompress.h,v 1.4 1994/09/21 06:50:08 paulus 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 #ifdef _KERNEL_OPT 46 #include "opt_inet.h" 47 #endif 48 49 #define MAX_STATES 16 /* must be > 2 and < 256 */ 50 #define MAX_HDR MLEN /* XXX 4bsd-ism: should really be 128 */ 51 52 /* 53 * Compressed packet format: 54 * 55 * The first octet contains the packet type (top 3 bits), TCP 56 * 'push' bit, and flags that indicate which of the 4 TCP sequence 57 * numbers have changed (bottom 5 bits). The next octet is a 58 * conversation number that associates a saved IP/TCP header with 59 * the compressed packet. The next two octets are the TCP checksum 60 * from the original datagram. The next 0 to 15 octets are 61 * sequence number changes, one change per bit set in the header 62 * (there may be no changes and there are two special cases where 63 * the receiver implicitly knows what changed -- see below). 64 * 65 * There are 5 numbers which can change (they are always inserted 66 * in the following order): TCP urgent pointer, window, 67 * acknowledgement, sequence number and IP ID. (The urgent pointer 68 * is different from the others in that its value is sent, not the 69 * change in value.) Since typical use of SLIP links is biased 70 * toward small packets (see comments on MTU/MSS below), changes 71 * use a variable length coding with one octet for numbers in the 72 * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the 73 * range 256 - 65535 or 0. (If the change in sequence number or 74 * ack is more than 65535, an uncompressed packet is sent.) 75 */ 76 77 /* 78 * Packet types (must not conflict with IP protocol version) 79 * 80 * The top nibble of the first octet is the packet type. There are 81 * three possible types: IP (not proto TCP or tcp with one of the 82 * control flags set); uncompressed TCP (a normal IP/TCP packet but 83 * with the 8-bit protocol field replaced by an 8-bit connection id -- 84 * this type of packet syncs the sender & receiver); and compressed 85 * TCP (described above). 86 * 87 * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and 88 * is logically part of the 4-bit "changes" field that follows. Top 89 * three bits are actual packet type. For backward compatibility 90 * and in the interest of conserving bits, numbers are chosen so the 91 * IP protocol version number (4) which normally appears in this nibble 92 * means "IP packet". 93 */ 94 95 /* packet types */ 96 #define TYPE_IP 0x40 97 #define TYPE_UNCOMPRESSED_TCP 0x70 98 #define TYPE_COMPRESSED_TCP 0x80 99 #define TYPE_ERROR 0x00 100 101 /* Bits in first octet of compressed packet */ 102 #define NEW_C 0x40 /* flag bits for what changed in a packet */ 103 #define NEW_I 0x20 104 #define NEW_S 0x08 105 #define NEW_A 0x04 106 #define NEW_W 0x02 107 #define NEW_U 0x01 108 109 /* reserved, special-case values of above */ 110 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */ 111 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */ 112 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U) 113 114 #define TCP_PUSH_BIT 0x10 115 116 117 /* 118 * "state" data for each active tcp conversation on the wire. This is 119 * basically a copy of the entire IP/TCP header from the last packet 120 * we saw from the conversation together with a small identifier 121 * the transmit & receive ends of the line use to locate saved header. 122 */ 123 struct cstate { 124 struct cstate *cs_next; /* next most recently used cstate (xmit only) */ 125 uint16_t cs_hlen; /* size of hdr (receive only) */ 126 u_char cs_id; /* connection # associated with this state */ 127 u_char cs_filler; 128 union { 129 char csu_hdr[MAX_HDR]; 130 #ifdef INET 131 struct ip csu_ip; /* ip/tcp hdr from most recent packet */ 132 #endif 133 } slcs_u; 134 }; 135 #define cs_ip slcs_u.csu_ip 136 #define cs_hdr slcs_u.csu_hdr 137 138 /* 139 * all the state data for one serial line (we need one of these 140 * per line). 141 */ 142 struct slcompress { 143 struct cstate *last_cs; /* most recently used tstate */ 144 u_char last_recv; /* last rcvd conn. id */ 145 u_char last_xmit; /* last sent conn. id */ 146 uint16_t flags; 147 #ifndef SL_NO_STATS 148 int sls_packets; /* outbound packets */ 149 int sls_compressed; /* outbound compressed packets */ 150 int sls_searches; /* searches for connection state */ 151 int sls_misses; /* times couldn't find conn. state */ 152 int sls_uncompressedin; /* inbound uncompressed packets */ 153 int sls_compressedin; /* inbound compressed packets */ 154 int sls_errorin; /* inbound unknown type packets */ 155 int sls_tossed; /* inbound packets tossed because of error */ 156 #endif 157 struct cstate tstate[MAX_STATES]; /* xmit connection states */ 158 struct cstate rstate[MAX_STATES]; /* receive connection states */ 159 }; 160 /* flag values */ 161 #define SLF_TOSS 1 /* tossing rcvd frames because of input err */ 162 163 void sl_compress_init(struct slcompress *); 164 void sl_compress_setup(struct slcompress *, int); 165 #ifdef INET 166 u_int sl_compress_tcp(struct mbuf *, 167 struct ip *, struct slcompress *, int); 168 #endif 169 int sl_uncompress_tcp(u_char **, int, u_int, struct slcompress *); 170 int sl_uncompress_tcp_core(u_char *, int, int, u_int, 171 struct slcompress *, u_char **, u_int *); 172 173 #endif /* !_NET_SLCOMPRESS_H_ */ 174