1 /* 2 * Definitions for tcp compression routines. 3 * 4 * Copyright (c) 1989, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989: 36 * - Initial distribution. 37 * $FreeBSD: src/sys/net/slcompress.h,v 1.14.2.1 2000/05/05 13:37:06 jlemon Exp $ 38 * $DragonFly: src/sys/net/slcompress.h,v 1.3 2003/08/26 20:49:47 rob Exp $ 39 */ 40 41 #ifndef _NET_SLCOMPRESS_H_ 42 #define _NET_SLCOMPRESS_H_ 43 44 #define MAX_STATES 16 /* must be > 2 and < 256 */ 45 #define MAX_HDR 128 46 47 /* 48 * Compressed packet format: 49 * 50 * The first octet contains the packet type (top 3 bits), TCP 51 * 'push' bit, and flags that indicate which of the 4 TCP sequence 52 * numbers have changed (bottom 5 bits). The next octet is a 53 * conversation number that associates a saved IP/TCP header with 54 * the compressed packet. The next two octets are the TCP checksum 55 * from the original datagram. The next 0 to 15 octets are 56 * sequence number changes, one change per bit set in the header 57 * (there may be no changes and there are two special cases where 58 * the receiver implicitly knows what changed -- see below). 59 * 60 * There are 5 numbers which can change (they are always inserted 61 * in the following order): TCP urgent pointer, window, 62 * acknowledgement, sequence number and IP ID. (The urgent pointer 63 * is different from the others in that its value is sent, not the 64 * change in value.) Since typical use of SLIP links is biased 65 * toward small packets (see comments on MTU/MSS below), changes 66 * use a variable length coding with one octet for numbers in the 67 * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the 68 * range 256 - 65535 or 0. (If the change in sequence number or 69 * ack is more than 65535, an uncompressed packet is sent.) 70 */ 71 72 /* 73 * Packet types (must not conflict with IP protocol version) 74 * 75 * The top nibble of the first octet is the packet type. There are 76 * three possible types: IP (not proto TCP or tcp with one of the 77 * control flags set); uncompressed TCP (a normal IP/TCP packet but 78 * with the 8-bit protocol field replaced by an 8-bit connection id -- 79 * this type of packet syncs the sender & receiver); and compressed 80 * TCP (described above). 81 * 82 * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and 83 * is logically part of the 4-bit "changes" field that follows. Top 84 * three bits are actual packet type. For backward compatibility 85 * and in the interest of conserving bits, numbers are chosen so the 86 * IP protocol version number (4) which normally appears in this nibble 87 * means "IP packet". 88 */ 89 90 /* packet types */ 91 #define TYPE_IP 0x40 92 #define TYPE_UNCOMPRESSED_TCP 0x70 93 #define TYPE_COMPRESSED_TCP 0x80 94 #define TYPE_ERROR 0x00 95 96 /* Bits in first octet of compressed packet */ 97 #define NEW_C 0x40 /* flag bits for what changed in a packet */ 98 #define NEW_I 0x20 99 #define NEW_S 0x08 100 #define NEW_A 0x04 101 #define NEW_W 0x02 102 #define NEW_U 0x01 103 104 /* reserved, special-case values of above */ 105 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */ 106 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */ 107 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U) 108 109 #define TCP_PUSH_BIT 0x10 110 111 112 /* 113 * "state" data for each active tcp conversation on the wire. This is 114 * basically a copy of the entire IP/TCP header from the last packet 115 * we saw from the conversation together with a small identifier 116 * the transmit & receive ends of the line use to locate saved header. 117 */ 118 struct cstate { 119 struct cstate *cs_next; /* next most recently used cstate (xmit only) */ 120 u_int16_t cs_hlen; /* size of hdr (receive only) */ 121 u_char cs_id; /* connection # associated with this state */ 122 u_char cs_filler; 123 union { 124 char csu_hdr[MAX_HDR]; 125 struct ip csu_ip; /* ip/tcp hdr from most recent packet */ 126 } slcs_u; 127 }; 128 #define cs_ip slcs_u.csu_ip 129 #define cs_hdr slcs_u.csu_hdr 130 131 /* 132 * all the state data for one serial line (we need one of these 133 * per line). 134 */ 135 struct slcompress { 136 struct cstate *last_cs; /* most recently used tstate */ 137 u_char last_recv; /* last rcvd conn. id */ 138 u_char last_xmit; /* last sent conn. id */ 139 u_int16_t flags; 140 #ifndef SL_NO_STATS 141 int sls_packets; /* outbound packets */ 142 int sls_compressed; /* outbound compressed packets */ 143 int sls_searches; /* searches for connection state */ 144 int sls_misses; /* times couldn't find conn. state */ 145 int sls_uncompressedin; /* inbound uncompressed packets */ 146 int sls_compressedin; /* inbound compressed packets */ 147 int sls_errorin; /* inbound unknown type packets */ 148 int sls_tossed; /* inbound packets tossed because of error */ 149 #endif 150 struct cstate tstate[MAX_STATES]; /* xmit connection states */ 151 struct cstate rstate[MAX_STATES]; /* receive connection states */ 152 }; 153 /* flag values */ 154 #define SLF_TOSS 1 /* tossing rcvd frames because of input err */ 155 156 void sl_compress_init (struct slcompress *, int); 157 u_int sl_compress_tcp (struct mbuf *, 158 struct ip *, struct slcompress *, int); 159 int sl_uncompress_tcp (u_char **, int, u_int, struct slcompress *); 160 int sl_uncompress_tcp_core (u_char *, int, int, u_int, 161 struct slcompress *, u_char **, u_int *); 162 163 #endif /* !_NET_SLCOMPRESS_H_ */ 164