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 #ifdef __cplusplus 32 extern "C" { 33 #endif 34 35 #define MAX_STATES 16 /* must be > 2 and < 256 */ 36 #define MAX_HDR 128 37 38 /* 39 * Compressed packet format: 40 * 41 * The first octet contains the packet type (top 3 bits), TCP 42 * 'push' bit, and flags that indicate which of the 4 TCP sequence 43 * numbers have changed (bottom 5 bits). The next octet is a 44 * conversation number that associates a saved IP/TCP header with 45 * the compressed packet. The next two octets are the TCP checksum 46 * from the original datagram. The next 0 to 15 octets are 47 * sequence number changes, one change per bit set in the header 48 * (there may be no changes and there are two special cases where 49 * the receiver implicitly knows what changed -- see below). 50 * 51 * There are 5 numbers which can change (they are always inserted 52 * in the following order): TCP urgent pointer, window, 53 * acknowlegement, sequence number and IP ID. (The urgent pointer 54 * is different from the others in that its value is sent, not the 55 * change in value.) Since typical use of SLIP links is biased 56 * toward small packets (see comments on MTU/MSS below), changes 57 * use a variable length coding with one octet for numbers in the 58 * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the 59 * range 256 - 65535 or 0. (If the change in sequence number or 60 * ack is more than 65535, an uncompressed packet is sent.) 61 */ 62 63 /* 64 * Packet types (must not conflict with IP protocol version) 65 * 66 * The top nibble of the first octet is the packet type. There are 67 * three possible types: IP (not proto TCP or tcp with one of the 68 * control flags set); uncompressed TCP (a normal IP/TCP packet but 69 * with the 8-bit protocol field replaced by an 8-bit connection id -- 70 * this type of packet syncs the sender & receiver); and compressed 71 * TCP (described above). 72 * 73 * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and 74 * is logically part of the 4-bit "changes" field that follows. Top 75 * three bits are actual packet type. For backward compatibility 76 * and in the interest of conserving bits, numbers are chosen so the 77 * IP protocol version number (4) which normally appears in this nibble 78 * means "IP packet". 79 */ 80 81 /* packet types */ 82 #define TYPE_IP 0x40 83 #define TYPE_UNCOMPRESSED_TCP 0x70 84 #define TYPE_COMPRESSED_TCP 0x80 85 #define TYPE_ERROR 0x00 86 87 /* Bits in first octet of compressed packet */ 88 #define NEW_C 0x40 /* flag bits for what changed in a packet */ 89 #define NEW_I 0x20 90 #define NEW_S 0x08 91 #define NEW_A 0x04 92 #define NEW_W 0x02 93 #define NEW_U 0x01 94 95 /* reserved, special-case values of above */ 96 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */ 97 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */ 98 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U) 99 100 #define TCP_PUSH_BIT 0x10 101 102 103 /* 104 * "state" data for each active tcp conversation on the wire. This is 105 * basically a copy of the entire IP/TCP header from the last packet 106 * we saw from the conversation together with a small identifier 107 * the transmit & receive ends of the line use to locate saved header. 108 */ 109 struct cstate { 110 struct cstate *cs_next; /* next most recently used state (xmit only) */ 111 ushort_t cs_hlen; /* size of hdr (receive only) */ 112 uchar_t cs_id; /* connection # associated with this state */ 113 uchar_t cs_filler; 114 union { 115 char csu_hdr[MAX_HDR]; 116 struct ip csu_ip; /* ip/tcp hdr from most recent packet */ 117 } vjcs_u; 118 }; 119 #define cs_ip vjcs_u.csu_ip 120 #define cs_hdr vjcs_u.csu_hdr 121 122 /* 123 * all the state data for one serial line (we need one of these per line). 124 */ 125 struct vjcompress { 126 struct cstate *last_cs; /* most recently used tstate */ 127 uchar_t last_recv; /* last rcvd conn. id */ 128 uchar_t last_xmit; /* last sent conn. id */ 129 ushort_t flags; 130 #ifndef VJ_NO_STATS 131 struct vjstat stats; 132 #endif 133 struct cstate tstate[MAX_STATES]; /* xmit connection states */ 134 struct cstate rstate[MAX_STATES]; /* receive connection states */ 135 }; 136 137 /* flag values */ 138 #define VJF_TOSS 1 /* tossing rcvd frames because of input err */ 139 140 extern void vj_compress_init __P((struct vjcompress *comp, int max_state)); 141 extern uint_t vj_compress_tcp __P((struct ip *ip, uint_t mlen, 142 struct vjcompress *comp, int compress_cid_flag, 143 uchar_t **vjhdrp)); 144 extern void vj_uncompress_err __P((struct vjcompress *comp)); 145 extern int vj_uncompress_uncomp __P((uchar_t *buf, int buflen, 146 struct vjcompress *comp)); 147 extern int vj_uncompress_tcp __P((uchar_t *buf, int buflen, int total_len, 148 struct vjcompress *comp, uchar_t **hdrp, 149 uint_t *hlenp)); 150 151 #ifdef __cplusplus 152 } 153 #endif 154 155 #endif /* _VJCOMPRESS_H_ */ 156