2 * Definitions for tcp compression routines.
4 * $Id: vj.h,v 1.5 2007/12/19 20:47:23 fbernon Exp $
6 * Copyright (c) 1989 Regents of the University of California.
9 * Redistribution and use in source and binary forms are permitted
10 * provided that the above copyright notice and this paragraph are
11 * duplicated in all such forms and that any documentation,
12 * advertising materials, and other materials related to such
13 * distribution and use acknowledge that the software was developed
14 * by the University of California, Berkeley. The name of the
15 * University may not be used to endorse or promote products derived
16 * from this software without specific prior written permission.
17 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
19 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
21 * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
22 * - Initial distribution.
30 #define MAX_SLOTS 16 /* must be > 2 and < 256 */
34 * Compressed packet format:
36 * The first octet contains the packet type (top 3 bits), TCP
37 * 'push' bit, and flags that indicate which of the 4 TCP sequence
38 * numbers have changed (bottom 5 bits). The next octet is a
39 * conversation number that associates a saved IP/TCP header with
40 * the compressed packet. The next two octets are the TCP checksum
41 * from the original datagram. The next 0 to 15 octets are
42 * sequence number changes, one change per bit set in the header
43 * (there may be no changes and there are two special cases where
44 * the receiver implicitly knows what changed -- see below).
46 * There are 5 numbers which can change (they are always inserted
47 * in the following order): TCP urgent pointer, window,
48 * acknowlegement, sequence number and IP ID. (The urgent pointer
49 * is different from the others in that its value is sent, not the
50 * change in value.) Since typical use of SLIP links is biased
51 * toward small packets (see comments on MTU/MSS below), changes
52 * use a variable length coding with one octet for numbers in the
53 * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
54 * range 256 - 65535 or 0. (If the change in sequence number or
55 * ack is more than 65535, an uncompressed packet is sent.)
59 * Packet types (must not conflict with IP protocol version)
61 * The top nibble of the first octet is the packet type. There are
62 * three possible types: IP (not proto TCP or tcp with one of the
63 * control flags set); uncompressed TCP (a normal IP/TCP packet but
64 * with the 8-bit protocol field replaced by an 8-bit connection id --
65 * this type of packet syncs the sender & receiver); and compressed
66 * TCP (described above).
68 * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
69 * is logically part of the 4-bit "changes" field that follows. Top
70 * three bits are actual packet type. For backward compatibility
71 * and in the interest of conserving bits, numbers are chosen so the
72 * IP protocol version number (4) which normally appears in this nibble
78 #define TYPE_UNCOMPRESSED_TCP 0x70
79 #define TYPE_COMPRESSED_TCP 0x80
80 #define TYPE_ERROR 0x00
82 /* Bits in first octet of compressed packet */
83 #define NEW_C 0x40 /* flag bits for what changed in a packet */
90 /* reserved, special-case values of above */
91 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */
92 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */
93 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
95 #define TCP_PUSH_BIT 0x10
99 * "state" data for each active tcp conversation on the wire. This is
100 * basically a copy of the entire IP/TCP header from the last packet
101 * we saw from the conversation together with a small identifier
102 * the transmit & receive ends of the line use to locate saved header.
105 struct cstate *cs_next; /* next most recently used state (xmit only) */
106 u_short cs_hlen; /* size of hdr (receive only) */
107 u_char cs_id; /* connection # associated with this state */
110 char csu_hdr[MAX_HDR];
111 struct ip csu_ip; /* ip/tcp hdr from most recent packet */
114 #define cs_ip vjcs_u.csu_ip
115 #define cs_hdr vjcs_u.csu_hdr
119 unsigned long vjs_packets; /* outbound packets */
120 unsigned long vjs_compressed; /* outbound compressed packets */
121 unsigned long vjs_searches; /* searches for connection state */
122 unsigned long vjs_misses; /* times couldn't find conn. state */
123 unsigned long vjs_uncompressedin; /* inbound uncompressed packets */
124 unsigned long vjs_compressedin; /* inbound compressed packets */
125 unsigned long vjs_errorin; /* inbound unknown type packets */
126 unsigned long vjs_tossed; /* inbound packets tossed because of error */
130 * all the state data for one serial line (we need one of these per line).
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 u_char compressSlot; /* Flag indicating OK to compress slot ID. */
142 struct cstate tstate[MAX_SLOTS]; /* xmit connection states */
143 struct cstate rstate[MAX_SLOTS]; /* receive connection states */
147 #define VJF_TOSS 1U /* tossing rcvd frames because of input err */
149 extern void vj_compress_init (struct vjcompress *comp);
150 extern u_int vj_compress_tcp (struct vjcompress *comp, struct pbuf *pb);
151 extern void vj_uncompress_err (struct vjcompress *comp);
152 extern int vj_uncompress_uncomp(struct pbuf *nb, struct vjcompress *comp);
153 extern int vj_uncompress_tcp (struct pbuf **nb, struct vjcompress *comp);
git.joshuawise.com / netwatch.git / blob