1 /* 2 * Definitions for tcp compression routines. 3 * 4 * $Id: vjcompress.h,v 1.3 1996/05/28 00:55:33 paulus Exp $ 5 * 6 * Copyright (c) 2000 by Sun Microsystems, Inc. 7 * All rights reserved. 8 * 9 * Copyright (c) 1989 Regents of the University of California. 10 * All rights reserved. 11 * 12 * Redistribution and use in source and binary forms are permitted 13 * provided that the above copyright notice and this paragraph are 14 * duplicated in all such forms and that any documentation, 15 * advertising materials, and other materials related to such 16 * distribution and use acknowledge that the software was developed 17 * by the University of California, Berkeley. The name of the 18 * University may not be used to endorse or promote products derived 19 * from this software without specific prior written permission. 20 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR 21 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED 22 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. 23 * 24 * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989: 25 * - Initial distribution. 26 */ 27 28 #ifndef _VJCOMPRESS_H_ 29 #define _VJCOMPRESS_H_ 30 31 #pragma ident "%Z%%M% %I% %E% SMI" 32 33 #ifdef __cplusplus 34 extern "C" { 35 #endif 36 37 #define MAX_STATES 16 /* must be > 2 and < 256 */ 38 #define MAX_HDR 128 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 * acknowlegement, 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 /* packet types */ 84 #define TYPE_IP 0x40 85 #define TYPE_UNCOMPRESSED_TCP 0x70 86 #define TYPE_COMPRESSED_TCP 0x80 87 #define TYPE_ERROR 0x00 88 89 /* Bits in first octet of compressed packet */ 90 #define NEW_C 0x40 /* flag bits for what changed in a packet */ 91 #define NEW_I 0x20 92 #define NEW_S 0x08 93 #define NEW_A 0x04 94 #define NEW_W 0x02 95 #define NEW_U 0x01 96 97 /* reserved, special-case values of above */ 98 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */ 99 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */ 100 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U) 101 102 #define TCP_PUSH_BIT 0x10 103 104 105 /* 106 * "state" data for each active tcp conversation on the wire. This is 107 * basically a copy of the entire IP/TCP header from the last packet 108 * we saw from the conversation together with a small identifier 109 * the transmit & receive ends of the line use to locate saved header. 110 */ 111 struct cstate { 112 struct cstate *cs_next; /* next most recently used state (xmit only) */ 113 ushort_t cs_hlen; /* size of hdr (receive only) */ 114 uchar_t cs_id; /* connection # associated with this state */ 115 uchar_t cs_filler; 116 union { 117 char csu_hdr[MAX_HDR]; 118 struct ip csu_ip; /* ip/tcp hdr from most recent packet */ 119 } vjcs_u; 120 }; 121 #define cs_ip vjcs_u.csu_ip 122 #define cs_hdr vjcs_u.csu_hdr 123 124 /* 125 * all the state data for one serial line (we need one of these per line). 126 */ 127 struct vjcompress { 128 struct cstate *last_cs; /* most recently used tstate */ 129 uchar_t last_recv; /* last rcvd conn. id */ 130 uchar_t last_xmit; /* last sent conn. id */ 131 ushort_t flags; 132 #ifndef VJ_NO_STATS 133 struct vjstat stats; 134 #endif 135 struct cstate tstate[MAX_STATES]; /* xmit connection states */ 136 struct cstate rstate[MAX_STATES]; /* receive connection states */ 137 }; 138 139 /* flag values */ 140 #define VJF_TOSS 1 /* tossing rcvd frames because of input err */ 141 142 extern void vj_compress_init __P((struct vjcompress *comp, int max_state)); 143 extern uint_t vj_compress_tcp __P((struct ip *ip, uint_t mlen, 144 struct vjcompress *comp, int compress_cid_flag, 145 uchar_t **vjhdrp)); 146 extern void vj_uncompress_err __P((struct vjcompress *comp)); 147 extern int vj_uncompress_uncomp __P((uchar_t *buf, int buflen, 148 struct vjcompress *comp)); 149 extern int vj_uncompress_tcp __P((uchar_t *buf, int buflen, int total_len, 150 struct vjcompress *comp, uchar_t **hdrp, 151 uint_t *hlenp)); 152 153 #ifdef __cplusplus 154 } 155 #endif 156 157 #endif /* _VJCOMPRESS_H_ */ 158