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