1 /*!\file net/slcompre.h
2 * SLIP/PPP compression.
5 /* $NetBSD: slcompress.h,v 1.11 1997/05/17 21:12:11 christos Exp $ */
6 /* Id: slcompress.h,v 1.4 1994/09/21 06:50:08 paulus Exp */
9 * Copyright (c) 1989, 1993
10 * The Regents of the University of California. All rights reserved.
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. All advertising materials mentioning features or use of this software
21 * must display the following acknowledgement:
22 * This product includes software developed by the University of
23 * California, Berkeley and its contributors.
24 * 4. Neither the name of the University nor the names of its contributors
25 * may be used to endorse or promote products derived from this software
26 * without specific prior written permission.
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
40 * @(#)slcompress.h 8.1 (Berkeley) 6/10/93
44 * Definitions for tcp compression routines.
46 * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
47 * - Initial distribution.
50 #ifndef __NET_SLCOMPRESS_H
51 #define __NET_SLCOMPRESS_H
57 #define MAX_STATES 16 /* must be > 2 and < 256 */
58 #define MAX_HDR MLEN /* XXX 4bsd-ism: should really be 128 */
61 * Compressed packet format:
63 * The first octet contains the packet type (top 3 bits), TCP
64 * 'push' bit, and flags that indicate which of the 4 TCP sequence
65 * numbers have changed (bottom 5 bits). The next octet is a
66 * conversation number that associates a saved IP/TCP header with
67 * the compressed packet. The next two octets are the TCP checksum
68 * from the original datagram. The next 0 to 15 octets are
69 * sequence number changes, one change per bit set in the header
70 * (there may be no changes and there are two special cases where
71 * the receiver implicitly knows what changed -- see below).
73 * There are 5 numbers which can change (they are always inserted
74 * in the following order): TCP urgent pointer, window,
75 * acknowlegement, sequence number and IP ID. (The urgent pointer
76 * is different from the others in that its value is sent, not the
77 * change in value.) Since typical use of SLIP links is biased
78 * toward small packets (see comments on MTU/MSS below), changes
79 * use a variable length coding with one octet for numbers in the
80 * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
81 * range 256 - 65535 or 0. (If the change in sequence number or
82 * ack is more than 65535, an uncompressed packet is sent.)
86 * Packet types (must not conflict with IP protocol version)
88 * The top nibble of the first octet is the packet type. There are
89 * three possible types: IP (not proto TCP or tcp with one of the
90 * control flags set); uncompressed TCP (a normal IP/TCP packet but
91 * with the 8-bit protocol field replaced by an 8-bit connection id --
92 * this type of packet syncs the sender & receiver); and compressed
93 * TCP (described above).
95 * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
96 * is logically part of the 4-bit "changes" field that follows. Top
97 * three bits are actual packet type. For backward compatibility
98 * and in the interest of conserving bits, numbers are chosen so the
99 * IP protocol version number (4) which normally appears in this nibble
105 #define TYPE_UNCOMPRESSED_TCP 0x70
106 #define TYPE_COMPRESSED_TCP 0x80
107 #define TYPE_ERROR 0x00
109 /* Bits in first octet of compressed packet */
110 #define NEW_C 0x40 /* flag bits for what changed in a packet */
117 /* reserved, special-case values of above */
118 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */
119 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */
120 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
122 #define TCP_PUSH_BIT 0x10
126 * "state" data for each active tcp conversation on the wire. This is
127 * basically a copy of the entire IP/TCP header from the last packet
128 * we saw from the conversation together with a small identifier
129 * the transmit & receive ends of the line use to locate saved header.
132 struct cstate *cs_next; /* next most recently used cstate (xmit only) */
133 u_int16_t cs_hlen; /* size of hdr (receive only) */
134 u_char cs_id; /* connection # associated with this state */
137 char csu_hdr[MAX_HDR];
138 struct ip csu_ip; /* ip/tcp hdr from most recent packet */
141 #define cs_ip slcs_u.csu_ip
142 #define cs_hdr slcs_u.csu_hdr
145 * all the state data for one serial line (we need one of these
149 struct cstate *last_cs; /* most recently used tstate */
150 u_char last_recv; /* last rcvd conn. id */
151 u_char last_xmit; /* last sent conn. id */
154 int sls_packets; /* outbound packets */
155 int sls_compressed; /* outbound compressed packets */
156 int sls_searches; /* searches for connection state */
157 int sls_misses; /* times couldn't find conn. state */
158 int sls_uncompressedin; /* inbound uncompressed packets */
159 int sls_compressedin; /* inbound compressed packets */
160 int sls_errorin; /* inbound unknown type packets */
161 int sls_tossed; /* inbound packets tossed because of error */
163 struct cstate tstate[MAX_STATES]; /* xmit connection states */
164 struct cstate rstate[MAX_STATES]; /* receive connection states */
167 #define SLF_TOSS 1 /* tossing rcvd frames because of input err */
169 void sl_compress_init (struct slcompress *);
170 void sl_compress_setup (struct slcompress *, int);
171 u_int sl_compress_tcp (struct mbuf *, struct ip *, struct slcompress *, int);
172 int sl_uncompress_tcp (u_char **, int, u_int, struct slcompress *);
173 int sl_uncompress_tcp_core (u_char *, int, int, u_int, struct slcompress *, u_char **, u_int *);