FreeBSD/Linux Kernel Cross Reference
sys/net/slcompress.h
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: releng/5.1/sys/net/slcompress.h 92725 2002-03-19 21:54:18Z alfred $
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_ */
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