1/*
2 * Definitions for tcp compression routines.
3 *
4 * $Id: vjcompress.h,v 1.3 1996/05/28 00:55:33 paulus Exp $
5 *
6 * Copyright (c) 2000 by Sun Microsystems, Inc.
7 * All rights reserved.
8 *
9 * Copyright (c) 1989 Regents of the University of California.
10 * All rights reserved.
11 *
12 * Redistribution and use in source and binary forms are permitted
13 * provided that the above copyright notice and this paragraph are
14 * duplicated in all such forms and that any documentation,
15 * advertising materials, and other materials related to such
16 * distribution and use acknowledge that the software was developed
17 * by the University of California, Berkeley.  The name of the
18 * University may not be used to endorse or promote products derived
19 * from this software without specific prior written permission.
20 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
21 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
22 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
23 *
24 *	Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
25 *	- Initial distribution.
26 */
27
28#ifndef _VJCOMPRESS_H_
29#define	_VJCOMPRESS_H_
30
31#pragma ident	"%Z%%M%	%I%	%E% SMI"
32
33#ifdef __cplusplus
34extern "C" {
35#endif
36
37#define	MAX_STATES 16		/* must be > 2 and < 256 */
38#define	MAX_HDR	   128
39
40/*
41 * Compressed packet format:
42 *
43 * The first octet contains the packet type (top 3 bits), TCP
44 * 'push' bit, and flags that indicate which of the 4 TCP sequence
45 * numbers have changed (bottom 5 bits).  The next octet is a
46 * conversation number that associates a saved IP/TCP header with
47 * the compressed packet.  The next two octets are the TCP checksum
48 * from the original datagram.  The next 0 to 15 octets are
49 * sequence number changes, one change per bit set in the header
50 * (there may be no changes and there are two special cases where
51 * the receiver implicitly knows what changed -- see below).
52 *
53 * There are 5 numbers which can change (they are always inserted
54 * in the following order): TCP urgent pointer, window,
55 * acknowlegement, sequence number and IP ID.  (The urgent pointer
56 * is different from the others in that its value is sent, not the
57 * change in value.)  Since typical use of SLIP links is biased
58 * toward small packets (see comments on MTU/MSS below), changes
59 * use a variable length coding with one octet for numbers in the
60 * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
61 * range 256 - 65535 or 0.  (If the change in sequence number or
62 * ack is more than 65535, an uncompressed packet is sent.)
63 */
64
65/*
66 * Packet types (must not conflict with IP protocol version)
67 *
68 * The top nibble of the first octet is the packet type.  There are
69 * three possible types: IP (not proto TCP or tcp with one of the
70 * control flags set); uncompressed TCP (a normal IP/TCP packet but
71 * with the 8-bit protocol field replaced by an 8-bit connection id --
72 * this type of packet syncs the sender & receiver); and compressed
73 * TCP (described above).
74 *
75 * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
76 * is logically part of the 4-bit "changes" field that follows.  Top
77 * three bits are actual packet type.  For backward compatibility
78 * and in the interest of conserving bits, numbers are chosen so the
79 * IP protocol version number (4) which normally appears in this nibble
80 * means "IP packet".
81 */
82
83/* packet types */
84#define	TYPE_IP 0x40
85#define	TYPE_UNCOMPRESSED_TCP 0x70
86#define	TYPE_COMPRESSED_TCP 0x80
87#define	TYPE_ERROR 0x00
88
89/* Bits in first octet of compressed packet */
90#define	NEW_C	0x40	/* flag bits for what changed in a packet */
91#define	NEW_I	0x20
92#define	NEW_S	0x08
93#define	NEW_A	0x04
94#define	NEW_W	0x02
95#define	NEW_U	0x01
96
97/* reserved, special-case values of above */
98#define	SPECIAL_I (NEW_S|NEW_W|NEW_U)		/* echoed interactive traffic */
99#define	SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U)	/* unidirectional data */
100#define	SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
101
102#define	TCP_PUSH_BIT 0x10
103
104
105/*
106 * "state" data for each active tcp conversation on the wire.  This is
107 * basically a copy of the entire IP/TCP header from the last packet
108 * we saw from the conversation together with a small identifier
109 * the transmit & receive ends of the line use to locate saved header.
110 */
111struct cstate {
112	struct cstate *cs_next;	/* next most recently used state (xmit only) */
113	ushort_t cs_hlen;	/* size of hdr (receive only) */
114	uchar_t cs_id;		/* connection # associated with this state */
115	uchar_t cs_filler;
116	union {
117		char csu_hdr[MAX_HDR];
118		struct ip csu_ip; /* ip/tcp hdr from most recent packet */
119	} vjcs_u;
120};
121#define	cs_ip vjcs_u.csu_ip
122#define	cs_hdr vjcs_u.csu_hdr
123
124/*
125 * all the state data for one serial line (we need one of these per line).
126 */
127struct vjcompress {
128	struct cstate *last_cs;	/* most recently used tstate */
129	uchar_t last_recv;		/* last rcvd conn. id */
130	uchar_t last_xmit;		/* last sent conn. id */
131	ushort_t flags;
132#ifndef VJ_NO_STATS
133	struct vjstat stats;
134#endif
135	struct cstate tstate[MAX_STATES];	/* xmit connection states */
136	struct cstate rstate[MAX_STATES];	/* receive connection states */
137};
138
139/* flag values */
140#define	VJF_TOSS 1		/* tossing rcvd frames because of input err */
141
142extern void  vj_compress_init __P((struct vjcompress *comp, int max_state));
143extern uint_t vj_compress_tcp __P((struct ip *ip, uint_t mlen,
144				struct vjcompress *comp, int compress_cid_flag,
145				uchar_t **vjhdrp));
146extern void  vj_uncompress_err __P((struct vjcompress *comp));
147extern int   vj_uncompress_uncomp __P((uchar_t *buf, int buflen,
148				struct vjcompress *comp));
149extern int   vj_uncompress_tcp __P((uchar_t *buf, int buflen, int total_len,
150				struct vjcompress *comp, uchar_t **hdrp,
151				uint_t *hlenp));
152
153#ifdef __cplusplus
154}
155#endif
156
157#endif /* _VJCOMPRESS_H_ */
158