slcompress.h revision 1.5
1 /* 2 * Definitions for tcp compression routines. 3 * 4 * Copyright (c) 1989 Regents of the University of California. 5 * 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 (at) helios.ee.lbl.gov), Dec 31, 1989: 36 * - Initial distribution. 37 * 38 * Paul Mackerras (paulus (at) cs.anu.edu.au), June 1993: 39 * - added sl_uncompress_tcp_part. 40 * 41 * From: slcompress.h 7.4 90/06/28 42 * $Id: slcompress.h,v 1.5 1994/01/15 20:13:16 deraadt Exp $ 43 */ 44 45 #ifndef _SLCOMPRESS_H_ 46 #define _SLCOMPRESS_H_ 47 48 #define MAX_STATES 16 /* must be > 2 and < 256 */ 49 #define MAX_HDR MLEN /* XXX 4bsd-ism: should really be 128 */ 50 51 /* 52 * Compressed packet format: 53 * 54 * The first octet contains the packet type (top 3 bits), TCP 55 * 'push' bit, and flags that indicate which of the 4 TCP sequence 56 * numbers have changed (bottom 5 bits). The next octet is a 57 * conversation number that associates a saved IP/TCP header with 58 * the compressed packet. The next two octets are the TCP checksum 59 * from the original datagram. The next 0 to 15 octets are 60 * sequence number changes, one change per bit set in the header 61 * (there may be no changes and there are two special cases where 62 * the receiver implicitly knows what changed -- see below). 63 * 64 * There are 5 numbers which can change (they are always inserted 65 * in the following order): TCP urgent pointer, window, 66 * acknowlegement, sequence number and IP ID. (The urgent pointer 67 * is different from the others in that its value is sent, not the 68 * change in value.) Since typical use of SLIP links is biased 69 * toward small packets (see comments on MTU/MSS below), changes 70 * use a variable length coding with one octet for numbers in the 71 * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the 72 * range 256 - 65535 or 0. (If the change in sequence number or 73 * ack is more than 65535, an uncompressed packet is sent.) 74 */ 75 76 /* 77 * Packet types (must not conflict with IP protocol version) 78 * 79 * The top nibble of the first octet is the packet type. There are 80 * three possible types: IP (not proto TCP or tcp with one of the 81 * control flags set); uncompressed TCP (a normal IP/TCP packet but 82 * with the 8-bit protocol field replaced by an 8-bit connection id -- 83 * this type of packet syncs the sender & receiver); and compressed 84 * TCP (described above). 85 * 86 * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and 87 * is logically part of the 4-bit "changes" field that follows. Top 88 * three bits are actual packet type. For backward compatibility 89 * and in the interest of conserving bits, numbers are chosen so the 90 * IP protocol version number (4) which normally appears in this nibble 91 * means "IP packet". 92 */ 93 94 /* packet types */ 95 #define TYPE_IP 0x40 96 #define TYPE_UNCOMPRESSED_TCP 0x70 97 #define TYPE_COMPRESSED_TCP 0x80 98 #define TYPE_ERROR 0x00 99 100 /* Bits in first octet of compressed packet */ 101 #define NEW_C 0x40 /* flag bits for what changed in a packet */ 102 #define NEW_I 0x20 103 #define NEW_S 0x08 104 #define NEW_A 0x04 105 #define NEW_W 0x02 106 #define NEW_U 0x01 107 108 /* reserved, special-case values of above */ 109 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */ 110 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */ 111 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U) 112 113 #define TCP_PUSH_BIT 0x10 114 115 116 /* 117 * "state" data for each active tcp conversation on the wire. This is 118 * basically a copy of the entire IP/TCP header from the last packet 119 * we saw from the conversation together with a small identifier 120 * the transmit & receive ends of the line use to locate saved header. 121 */ 122 struct cstate { 123 struct cstate *cs_next; /* next most recently used cstate (xmit only) */ 124 u_short cs_hlen; /* size of hdr (receive only) */ 125 u_char cs_id; /* connection # associated with this state */ 126 u_char cs_filler; 127 union { 128 char csu_hdr[MAX_HDR]; 129 struct ip csu_ip; /* ip/tcp hdr from most recent packet */ 130 } slcs_u; 131 }; 132 #define cs_ip slcs_u.csu_ip 133 #define cs_hdr slcs_u.csu_hdr 134 135 /* 136 * all the state data for one serial line (we need one of these 137 * per line). 138 */ 139 struct slcompress { 140 struct cstate *last_cs; /* most recently used tstate */ 141 u_char last_recv; /* last rcvd conn. id */ 142 u_char last_xmit; /* last sent conn. id */ 143 u_short flags; 144 #ifndef SL_NO_STATS 145 int sls_packets; /* outbound packets */ 146 int sls_compressed; /* outbound compressed packets */ 147 int sls_searches; /* searches for connection state */ 148 int sls_misses; /* times couldn't find conn. state */ 149 int sls_uncompressedin; /* inbound uncompressed packets */ 150 int sls_compressedin; /* inbound compressed packets */ 151 int sls_errorin; /* inbound unknown type packets */ 152 int sls_tossed; /* inbound packets tossed because of error */ 153 #endif 154 struct cstate tstate[MAX_STATES]; /* xmit connection states */ 155 struct cstate rstate[MAX_STATES]; /* receive connection states */ 156 }; 157 /* flag values */ 158 #define SLF_TOSS 1 /* tossing rcvd frames because of input err */ 159 160 extern void sl_compress_init __P((struct slcompress *)); 161 extern u_char sl_compress_tcp __P((struct mbuf *m, struct ip *ip, 162 struct slcompress *, int comp_cid_flag)); 163 extern int sl_uncompress_tcp __P((u_char **bufp, int len, u_int type, 164 struct slcompress *)); 165 extern int sl_uncompress_tcp_part __P((u_char **bufp, int buflen, 166 int total_len, u_int type, 167 struct slcompress *)); 168 169 #endif /* _SLCOMPRESS_H_ */ 170
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