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