1 #ifndef _SLHC_H
2 #define _SLHC_H
3 /*
4 * Definitions for tcp compression routines.
5 *
6 * $Header: slcompress.h,v 1.10 89/12/31 08:53:02 van Exp $
7 *
8 * Copyright (c) 1989 Regents of the University of California.
9 * All rights reserved.
10 *
11 * Redistribution and use in source and binary forms are permitted
12 * provided that the above copyright notice and this paragraph are
13 * duplicated in all such forms and that any documentation,
14 * advertising materials, and other materials related to such
15 * distribution and use acknowledge that the software was developed
16 * by the University of California, Berkeley. The name of the
17 * University may not be used to endorse or promote products derived
18 * from this software without specific prior written permission.
19 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
20 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
21 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
22 *
23 * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
24 * - Initial distribution.
25 *
26 *
27 * modified for KA9Q Internet Software Package by
28 * Katie Stevens (dkstevens@ucdavis.edu)
29 * University of California, Davis
30 * Computing Services
31 * - 01-31-90 initial adaptation
32 *
33 * - Feb 1991 Bill_Simpson@um.cc.umich.edu
34 * variable number of conversation slots
35 * allow zero or one slots
36 * separate routines
37 * status display
38 */
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 * acknowledgment, 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
84 #include <linux/ip.h>
85 #include <linux/tcp.h>
86
87 /* SLIP compression masks for len/vers byte */
88 #define SL_TYPE_IP 0x40
89 #define SL_TYPE_UNCOMPRESSED_TCP 0x70
90 #define SL_TYPE_COMPRESSED_TCP 0x80
91 #define SL_TYPE_ERROR 0x00
92
93 /* Bits in first octet of compressed packet */
94 #define NEW_C 0x40 /* flag bits for what changed in a packet */
95 #define NEW_I 0x20
96 #define NEW_S 0x08
97 #define NEW_A 0x04
98 #define NEW_W 0x02
99 #define NEW_U 0x01
100
101 /* reserved, special-case values of above */
102 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */
103 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */
104 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
105
106 #define TCP_PUSH_BIT 0x10
107
108 /*
109 * data type and sizes conversion assumptions:
110 *
111 * VJ code KA9Q style generic
112 * u_char byte_t unsigned char 8 bits
113 * u_short int16 unsigned short 16 bits
114 * u_int int16 unsigned short 16 bits
115 * u_long unsigned long unsigned long 32 bits
116 * int int32 long 32 bits
117 */
118
119 typedef __u8 byte_t;
120 typedef __u32 int32;
121
122 /*
123 * "state" data for each active tcp conversation on the wire. This is
124 * basically a copy of the entire IP/TCP header from the last packet
125 * we saw from the conversation together with a small identifier
126 * the transmit & receive ends of the line use to locate saved header.
127 */
128 struct cstate {
129 byte_t cs_this; /* connection id number (xmit) */
130 bool initialized; /* true if initialized */
131 struct cstate *next; /* next in ring (xmit) */
132 struct iphdr cs_ip; /* ip/tcp hdr from most recent packet */
133 struct tcphdr cs_tcp;
134 unsigned char cs_ipopt[64];
135 unsigned char cs_tcpopt[64];
136 int cs_hsize;
137 };
138 #define NULLSLSTATE (struct cstate *)0
139
140 /*
141 * all the state data for one serial line (we need one of these per line).
142 */
143 struct slcompress {
144 struct cstate *tstate; /* transmit connection states (array)*/
145 struct cstate *rstate; /* receive connection states (array)*/
146
147 byte_t tslot_limit; /* highest transmit slot id (0-l)*/
148 byte_t rslot_limit; /* highest receive slot id (0-l)*/
149
150 byte_t xmit_oldest; /* oldest xmit in ring */
151 byte_t xmit_current; /* most recent xmit id */
152 byte_t recv_current; /* most recent rcvd id */
153
154 byte_t flags;
155 #define SLF_TOSS 0x01 /* tossing rcvd frames until id received */
156
157 int32 sls_o_nontcp; /* outbound non-TCP packets */
158 int32 sls_o_tcp; /* outbound TCP packets */
159 int32 sls_o_uncompressed; /* outbound uncompressed packets */
160 int32 sls_o_compressed; /* outbound compressed packets */
161 int32 sls_o_searches; /* searches for connection state */
162 int32 sls_o_misses; /* times couldn't find conn. state */
163
164 int32 sls_i_uncompressed; /* inbound uncompressed packets */
165 int32 sls_i_compressed; /* inbound compressed packets */
166 int32 sls_i_error; /* inbound error packets */
167 int32 sls_i_tossed; /* inbound packets tossed because of error */
168
169 int32 sls_i_runt;
170 int32 sls_i_badcheck;
171 };
172 #define NULLSLCOMPR (struct slcompress *)0
173
174 /* In slhc.c: */
175 struct slcompress *slhc_init(int rslots, int tslots);
176 void slhc_free(struct slcompress *comp);
177
178 int slhc_compress(struct slcompress *comp, unsigned char *icp, int isize,
179 unsigned char *ocp, unsigned char **cpp, int compress_cid);
180 int slhc_uncompress(struct slcompress *comp, unsigned char *icp, int isize);
181 int slhc_remember(struct slcompress *comp, unsigned char *icp, int isize);
182 int slhc_toss(struct slcompress *comp);
183
184 #endif /* _SLHC_H */