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slhc_vj.h
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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 ([email protected]), Dec 31, 1989:
24  * - Initial distribution.
25  *
26  *
27  * modified for KA9Q Internet Software Package by
28  * Katie Stevens ([email protected])
29  * University of California, Davis
30  * Computing Services
31  * - 01-31-90 initial adaptation
32  *
33  * - Feb 1991 [email protected]
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  struct cstate *next; /* next in ring (xmit) */
131  struct iphdr cs_ip; /* ip/tcp hdr from most recent packet */
132  struct tcphdr cs_tcp;
133  unsigned char cs_ipopt[64];
134  unsigned char cs_tcpopt[64];
135  int cs_hsize;
136 };
137 #define NULLSLSTATE (struct cstate *)0
138 
139 /*
140  * all the state data for one serial line (we need one of these per line).
141  */
142 struct slcompress {
143  struct cstate *tstate; /* transmit connection states (array)*/
144  struct cstate *rstate; /* receive connection states (array)*/
145 
146  byte_t tslot_limit; /* highest transmit slot id (0-l)*/
147  byte_t rslot_limit; /* highest receive slot id (0-l)*/
148 
149  byte_t xmit_oldest; /* oldest xmit in ring */
150  byte_t xmit_current; /* most recent xmit id */
151  byte_t recv_current; /* most recent rcvd id */
152 
154 #define SLF_TOSS 0x01 /* tossing rcvd frames until id received */
155 
156  int32 sls_o_nontcp; /* outbound non-TCP packets */
157  int32 sls_o_tcp; /* outbound TCP packets */
158  int32 sls_o_uncompressed; /* outbound uncompressed packets */
159  int32 sls_o_compressed; /* outbound compressed packets */
160  int32 sls_o_searches; /* searches for connection state */
161  int32 sls_o_misses; /* times couldn't find conn. state */
162 
163  int32 sls_i_uncompressed; /* inbound uncompressed packets */
164  int32 sls_i_compressed; /* inbound compressed packets */
165  int32 sls_i_error; /* inbound error packets */
166  int32 sls_i_tossed; /* inbound packets tossed because of error */
167 
170 };
171 #define NULLSLCOMPR (struct slcompress *)0
172 
173 /* In slhc.c: */
174 struct slcompress *slhc_init(int rslots, int tslots);
175 void slhc_free(struct slcompress *comp);
176 
177 int slhc_compress(struct slcompress *comp, unsigned char *icp, int isize,
178  unsigned char *ocp, unsigned char **cpp, int compress_cid);
179 int slhc_uncompress(struct slcompress *comp, unsigned char *icp, int isize);
180 int slhc_remember(struct slcompress *comp, unsigned char *icp, int isize);
181 int slhc_toss(struct slcompress *comp);
182 
183 #endif /* _SLHC_H */