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1.1 root 1: /* slcompress.h 7.4 90/06/28 */
2: /*
3: * Definitions for tcp compression routines.
4: *
5: * $Header: slcompress.h,v 1.10 89/12/31 08:53:02 van Exp $
6: *
7: * Copyright (c) 1989 Regents of the University of California.
8: * All rights reserved.
9: *
10: * Redistribution and use in source and binary forms, with or without
11: * modification, are permitted provided that the following conditions
12: * are met:
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. All advertising materials mentioning features or use of this software
19: * must display the following acknowledgement:
20: * This product includes software developed by the University of
21: * California, Berkeley and its contributors.
22: * 4. Neither the name of the University nor the names of its contributors
23: * may be used to endorse or promote products derived from this software
24: * without specific prior written permission.
25: *
26: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
27: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
28: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
29: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
30: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
31: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36: * SUCH DAMAGE.
37: *
38: * Van Jacobson ([email protected]), Dec 31, 1989:
39: * - Initial distribution.
40: */
41:
42: #define MAX_STATES 16 /* must be > 2 and < 256 */
43: #define MAX_HDR MLEN /* XXX 4bsd-ism: should really be 128 */
44:
45: /*
46: * Compressed packet format:
47: *
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).
57: *
58: * There are 5 numbers which can change (they are always inserted
59: * in the following order): TCP urgent pointer, window,
60: * acknowlegement, 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.)
68: */
69:
70: /*
71: * Packet types (must not conflict with IP protocol version)
72: *
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).
79: *
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
85: * means "IP packet".
86: */
87:
88: /* packet types */
89: #define TYPE_IP 0x40
90: #define TYPE_UNCOMPRESSED_TCP 0x70
91: #define TYPE_COMPRESSED_TCP 0x80
92: #define TYPE_ERROR 0x00
93:
94: /* Bits in first octet of compressed packet */
95: #define NEW_C 0x40 /* flag bits for what changed in a packet */
96: #define NEW_I 0x20
97: #define NEW_S 0x08
98: #define NEW_A 0x04
99: #define NEW_W 0x02
100: #define NEW_U 0x01
101:
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)
106:
107: #define TCP_PUSH_BIT 0x10
108:
109:
110: /*
111: * "state" data for each active tcp conversation on the wire. This is
112: * basically a copy of the entire IP/TCP header from the last packet
113: * we saw from the conversation together with a small identifier
114: * the transmit & receive ends of the line use to locate saved header.
115: */
116: struct cstate {
117: struct cstate *cs_next; /* next most recently used cstate (xmit only) */
118: u_short cs_hlen; /* size of hdr (receive only) */
119: u_char cs_id; /* connection # associated with this state */
120: u_char cs_filler;
121: union {
122: char csu_hdr[MAX_HDR];
123: struct ip csu_ip; /* ip/tcp hdr from most recent packet */
124: } slcs_u;
125: };
126: #define cs_ip slcs_u.csu_ip
127: #define cs_hdr slcs_u.csu_hdr
128:
129: /*
130: * all the state data for one serial line (we need one of these
131: * per line).
132: */
133: struct slcompress {
134: struct cstate *last_cs; /* most recently used tstate */
135: u_char last_recv; /* last rcvd conn. id */
136: u_char last_xmit; /* last sent conn. id */
137: u_short flags;
138: #ifndef SL_NO_STATS
139: int sls_packets; /* outbound packets */
140: int sls_compressed; /* outbound compressed packets */
141: int sls_searches; /* searches for connection state */
142: int sls_misses; /* times couldn't find conn. state */
143: int sls_uncompressedin; /* inbound uncompressed packets */
144: int sls_compressedin; /* inbound compressed packets */
145: int sls_errorin; /* inbound unknown type packets */
146: int sls_tossed; /* inbound packets tossed because of error */
147: #endif
148: struct cstate tstate[MAX_STATES]; /* xmit connection states */
149: struct cstate rstate[MAX_STATES]; /* receive connection states */
150: };
151: /* flag values */
152: #define SLF_TOSS 1 /* tossing rcvd frames because of input err */
153:
154: extern void sl_compress_init(/* struct slcompress * */);
155: extern u_char sl_compress_tcp(/* struct mbuf *, struct ip *,
156: struct slcompress *, int compress_cid_flag */);
157: extern int sl_uncompress_tcp(/* u_char **, int, u_char, struct slcompress * */);
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