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 1.17 2002/03/19 21:54:18 alfred Exp $ 38 */ 39 40 #ifndef _NET_SLCOMPRESS_H_ 41 #define _NET_SLCOMPRESS_H_ 42 43 #define MAX_STATES 16 /* must be > 2 and < 256 */ 44 #define MAX_HDR 128 45 46 /* 47 * Compressed packet format: 48 * 49 * The first octet contains the packet type (top 3 bits), TCP 50 * 'push' bit, and flags that indicate which of the 4 TCP sequence 51 * numbers have changed (bottom 5 bits). The next octet is a 52 * conversation number that associates a saved IP/TCP header with 53 * the compressed packet. The next two octets are the TCP checksum 54 * from the original datagram. The next 0 to 15 octets are 55 * sequence number changes, one change per bit set in the header 56 * (there may be no changes and there are two special cases where 57 * the receiver implicitly knows what changed -- see below). 58 * 59 * There are 5 numbers which can change (they are always inserted 60 * in the following order): TCP urgent pointer, window, 61 * acknowledgement, sequence number and IP ID. (The urgent pointer 62 * is different from the others in that its value is sent, not the 63 * change in value.) Since typical use of SLIP links is biased 64 * toward small packets (see comments on MTU/MSS below), changes 65 * use a variable length coding with one octet for numbers in the 66 * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the 67 * range 256 - 65535 or 0. (If the change in sequence number or 68 * ack is more than 65535, an uncompressed packet is sent.) 69 */ 70 71 /* 72 * Packet types (must not conflict with IP protocol version) 73 * 74 * The top nibble of the first octet is the packet type. There are 75 * three possible types: IP (not proto TCP or tcp with one of the 76 * control flags set); uncompressed TCP (a normal IP/TCP packet but 77 * with the 8-bit protocol field replaced by an 8-bit connection id -- 78 * this type of packet syncs the sender & receiver); and compressed 79 * TCP (described above). 80 * 81 * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and 82 * is logically part of the 4-bit "changes" field that follows. Top 83 * three bits are actual packet type. For backward compatibility 84 * and in the interest of conserving bits, numbers are chosen so the 85 * IP protocol version number (4) which normally appears in this nibble 86 * means "IP packet". 87 */ 88 89 /* packet types */ 90 #define TYPE_IP 0x40 91 #define TYPE_UNCOMPRESSED_TCP 0x70 92 #define TYPE_COMPRESSED_TCP 0x80 93 #define TYPE_ERROR 0x00 94 95 /* Bits in first octet of compressed packet */ 96 #define NEW_C 0x40 /* flag bits for what changed in a packet */ 97 #define NEW_I 0x20 98 #define NEW_S 0x08 99 #define NEW_A 0x04 100 #define NEW_W 0x02 101 #define NEW_U 0x01 102 103 /* reserved, special-case values of above */ 104 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */ 105 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */ 106 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U) 107 108 #define TCP_PUSH_BIT 0x10 109 110 111 /* 112 * "state" data for each active tcp conversation on the wire. This is 113 * basically a copy of the entire IP/TCP header from the last packet 114 * we saw from the conversation together with a small identifier 115 * the transmit & receive ends of the line use to locate saved header. 116 */ 117 struct cstate { 118 struct cstate *cs_next; /* next most recently used cstate (xmit only) */ 119 u_int16_t cs_hlen; /* size of hdr (receive only) */ 120 u_char cs_id; /* connection # associated with this state */ 121 u_char cs_filler; 122 union { 123 char csu_hdr[MAX_HDR]; 124 struct ip csu_ip; /* ip/tcp hdr from most recent packet */ 125 } slcs_u; 126 }; 127 #define cs_ip slcs_u.csu_ip 128 #define cs_hdr slcs_u.csu_hdr 129 130 /* 131 * all the state data for one serial line (we need one of these 132 * per line). 133 */ 134 struct slcompress { 135 struct cstate *last_cs; /* most recently used tstate */ 136 u_char last_recv; /* last rcvd conn. id */ 137 u_char last_xmit; /* last sent conn. id */ 138 u_int16_t flags; 139 #ifndef SL_NO_STATS 140 int sls_packets; /* outbound packets */ 141 int sls_compressed; /* outbound compressed packets */ 142 int sls_searches; /* searches for connection state */ 143 int sls_misses; /* times couldn't find conn. state */ 144 int sls_uncompressedin; /* inbound uncompressed packets */ 145 int sls_compressedin; /* inbound compressed packets */ 146 int sls_errorin; /* inbound unknown type packets */ 147 int sls_tossed; /* inbound packets tossed because of error */ 148 #endif 149 struct cstate tstate[MAX_STATES]; /* xmit connection states */ 150 struct cstate rstate[MAX_STATES]; /* receive connection states */ 151 }; 152 /* flag values */ 153 #define SLF_TOSS 1 /* tossing rcvd frames because of input err */ 154 155 void sl_compress_init(struct slcompress *, int); 156 u_int sl_compress_tcp(struct mbuf *, struct ip *, struct slcompress *, int); 157 int sl_uncompress_tcp(u_char **, int, u_int, struct slcompress *); 158 int sl_uncompress_tcp_core(u_char *, int, int, u_int, 159 struct slcompress *, u_char **, u_int *); 160 161 #endif /* !_NET_SLCOMPRESS_H_ */ 162