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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 (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 | 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 | |
153 | byte_t flags; |
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 | |
168 | int32 sls_i_runt; |
169 | int32 sls_i_badcheck; |
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 */ |
184 |
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