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vj.h
1 /*
2  * Definitions for tcp compression routines.
3  *
4  * $Id: vj.h,v 1.7 2010/02/22 17:52:09 goldsimon Exp $
5  *
6  * Copyright (c) 1989 Regents of the University of California.
7  * All rights reserved.
8  *
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.
20  *
21  * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
22  * - Initial distribution.
23  */
24 
25 #include "ppp_opts.h"
26 #if PPP_SUPPORT && VJ_SUPPORT /* don't build if not configured for use in ppp_opts.h */
27 
28 #ifndef VJ_H
29 #define VJ_H
30 
31 #ifdef __cplusplus
32 extern "C" {
33 #endif
34 
35 #define MAX_SLOTS 16 /* must be > 2 and < 256 */
36 #define MAX_HDR 128
37 
38 /*
39  * Compressed packet format:
40  *
41  * The first octet contains the packet type (top 3 bits), TCP
42  * 'push' bit, and flags that indicate which of the 4 TCP sequence
43  * numbers have changed (bottom 5 bits). The next octet is a
44  * conversation number that associates a saved IP/TCP header with
45  * the compressed packet. The next two octets are the TCP checksum
46  * from the original datagram. The next 0 to 15 octets are
47  * sequence number changes, one change per bit set in the header
48  * (there may be no changes and there are two special cases where
49  * the receiver implicitly knows what changed -- see below).
50  *
51  * There are 5 numbers which can change (they are always inserted
52  * in the following order): TCP urgent pointer, window,
53  * acknowlegement, sequence number and IP ID. (The urgent pointer
54  * is different from the others in that its value is sent, not the
55  * change in value.) Since typical use of SLIP links is biased
56  * toward small packets (see comments on MTU/MSS below), changes
57  * use a variable length coding with one octet for numbers in the
58  * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
59  * range 256 - 65535 or 0. (If the change in sequence number or
60  * ack is more than 65535, an uncompressed packet is sent.)
61  */
62 
63 /*
64  * Packet types (must not conflict with IP protocol version)
65  *
66  * The top nibble of the first octet is the packet type. There are
67  * three possible types: IP (not proto TCP or tcp with one of the
68  * control flags set); uncompressed TCP (a normal IP/TCP packet but
69  * with the 8-bit protocol field replaced by an 8-bit connection id --
70  * this type of packet syncs the sender & receiver); and compressed
71  * TCP (described above).
72  *
73  * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
74  * is logically part of the 4-bit "changes" field that follows. Top
75  * three bits are actual packet type. For backward compatibility
76  * and in the interest of conserving bits, numbers are chosen so the
77  * IP protocol version number (4) which normally appears in this nibble
78  * means "IP packet".
79  */
80 
81 /* packet types */
82 #define TYPE_IP 0x40
83 #define TYPE_UNCOMPRESSED_TCP 0x70
84 #define TYPE_COMPRESSED_TCP 0x80
85 #define TYPE_ERROR 0x00
86 
87 /* Bits in first octet of compressed packet */
88 #define NEW_C 0x40 /* flag bits for what changed in a packet */
89 #define NEW_I 0x20
90 #define NEW_S 0x08
91 #define NEW_A 0x04
92 #define NEW_W 0x02
93 #define NEW_U 0x01
94 
95 /* reserved, special-case values of above */
96 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */
97 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */
98 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
99 
100 #define TCP_PUSH_BIT 0x10
101 
102 
103 /*
104  * "state" data for each active tcp conversation on the wire. This is
105  * basically a copy of the entire IP/TCP header from the last packet
106  * we saw from the conversation together with a small identifier
107  * the transmit & receive ends of the line use to locate saved header.
108  */
109 struct cstate {
110  struct cstate *cs_next; /* next most recently used state (xmit only) */
111  u16_t cs_hlen; /* size of hdr (receive only) */
112  u8_t cs_id; /* connection # associated with this state */
113  u8_t cs_filler;
114  union {
115  char csu_hdr[MAX_HDR];
116  struct ip_hdr csu_ip; /* ip/tcp hdr from most recent packet */
117  } vjcs_u;
118 };
119 #define cs_ip vjcs_u.csu_ip
120 #define cs_hdr vjcs_u.csu_hdr
121 
122 
123 struct vjstat {
124  u32_t vjs_packets; /* outbound packets */
125  u32_t vjs_compressed; /* outbound compressed packets */
126  u32_t vjs_searches; /* searches for connection state */
127  u32_t vjs_misses; /* times couldn't find conn. state */
128  u32_t vjs_uncompressedin; /* inbound uncompressed packets */
129  u32_t vjs_compressedin; /* inbound compressed packets */
130  u32_t vjs_errorin; /* inbound unknown type packets */
131  u32_t vjs_tossed; /* inbound packets tossed because of error */
132 };
133 
134 /*
135  * all the state data for one serial line (we need one of these per line).
136  */
137 struct vjcompress {
138  struct cstate *last_cs; /* most recently used tstate */
139  u8_t last_recv; /* last rcvd conn. id */
140  u8_t last_xmit; /* last sent conn. id */
141  u16_t flags;
142  u8_t maxSlotIndex;
143  u8_t compressSlot; /* Flag indicating OK to compress slot ID. */
144 #if LINK_STATS
145  struct vjstat stats;
146 #endif
147  struct cstate tstate[MAX_SLOTS]; /* xmit connection states */
148  struct cstate rstate[MAX_SLOTS]; /* receive connection states */
149 };
150 
151 /* flag values */
152 #define VJF_TOSS 1U /* tossing rcvd frames because of input err */
153 
154 extern void vj_compress_init (struct vjcompress *comp);
155 extern u8_t vj_compress_tcp (struct vjcompress *comp, struct pbuf **pb);
156 extern void vj_uncompress_err (struct vjcompress *comp);
157 extern int vj_uncompress_uncomp(struct pbuf *nb, struct vjcompress *comp);
158 extern int vj_uncompress_tcp (struct pbuf **nb, struct vjcompress *comp);
159 
160 #ifdef __cplusplus
161 }
162 #endif
163 
164 #endif /* VJ_H */
165 
166 #endif /* PPP_SUPPORT && VJ_SUPPORT */
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