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 119typedef __u8 byte_t; 120typedef __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 */ 128struct 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 */ 142struct 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: */ 174struct slcompress *slhc_init(int rslots, int tslots); 175void slhc_free(struct slcompress *comp); 176 177int slhc_compress(struct slcompress *comp, unsigned char *icp, int isize, 178 unsigned char *ocp, unsigned char **cpp, int compress_cid); 179int slhc_uncompress(struct slcompress *comp, unsigned char *icp, int isize); 180int slhc_remember(struct slcompress *comp, unsigned char *icp, int isize); 181int slhc_toss(struct slcompress *comp); 182 183#endif /* _SLHC_H */ 184