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