1 /* 2 * Definitions for tcp compression routines. 3 * 4 * $Id: vj.h,v 1.7 2010/02/22 17:52:09 goldsimon Exp $ 5 * 6 * Copyright (c) 1989 Regents of the University of California. 7 * All rights reserved. 8 * 9 * Redistribution and use in source and binary forms are permitted 10 * provided that the above copyright notice and this paragraph are 11 * duplicated in all such forms and that any documentation, 12 * advertising materials, and other materials related to such 13 * distribution and use acknowledge that the software was developed 14 * by the University of California, Berkeley. The name of the 15 * University may not be used to endorse or promote products derived 16 * from this software without specific prior written permission. 17 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED 19 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. 20 * 21 * Van Jacobson (van (at) helios.ee.lbl.gov), Dec 31, 1989: 22 * - Initial distribution. 23 */ 24 25 #ifndef VJ_H 26 #define VJ_H 27 28 #include "lwip/ip.h" 29 #include "lwip/tcp_impl.h" 30 31 #define MAX_SLOTS 16 /* must be > 2 and < 256 */ 32 #define MAX_HDR 128 33 34 /* 35 * Compressed packet format: 36 * 37 * The first octet contains the packet type (top 3 bits), TCP 38 * 'push' bit, and flags that indicate which of the 4 TCP sequence 39 * numbers have changed (bottom 5 bits). The next octet is a 40 * conversation number that associates a saved IP/TCP header with 41 * the compressed packet. The next two octets are the TCP checksum 42 * from the original datagram. The next 0 to 15 octets are 43 * sequence number changes, one change per bit set in the header 44 * (there may be no changes and there are two special cases where 45 * the receiver implicitly knows what changed -- see below). 46 * 47 * There are 5 numbers which can change (they are always inserted 48 * in the following order): TCP urgent pointer, window, 49 * acknowlegement, sequence number and IP ID. (The urgent pointer 50 * is different from the others in that its value is sent, not the 51 * change in value.) Since typical use of SLIP links is biased 52 * toward small packets (see comments on MTU/MSS below), changes 53 * use a variable length coding with one octet for numbers in the 54 * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the 55 * range 256 - 65535 or 0. (If the change in sequence number or 56 * ack is more than 65535, an uncompressed packet is sent.) 57 */ 58 59 /* 60 * Packet types (must not conflict with IP protocol version) 61 * 62 * The top nibble of the first octet is the packet type. There are 63 * three possible types: IP (not proto TCP or tcp with one of the 64 * control flags set); uncompressed TCP (a normal IP/TCP packet but 65 * with the 8-bit protocol field replaced by an 8-bit connection id -- 66 * this type of packet syncs the sender & receiver); and compressed 67 * TCP (described above). 68 * 69 * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and 70 * is logically part of the 4-bit "changes" field that follows. Top 71 * three bits are actual packet type. For backward compatibility 72 * and in the interest of conserving bits, numbers are chosen so the 73 * IP protocol version number (4) which normally appears in this nibble 74 * means "IP packet". 75 */ 76 77 /* packet types */ 78 #define TYPE_IP 0x40 79 #define TYPE_UNCOMPRESSED_TCP 0x70 80 #define TYPE_COMPRESSED_TCP 0x80 81 #define TYPE_ERROR 0x00 82 83 /* Bits in first octet of compressed packet */ 84 #define NEW_C 0x40 /* flag bits for what changed in a packet */ 85 #define NEW_I 0x20 86 #define NEW_S 0x08 87 #define NEW_A 0x04 88 #define NEW_W 0x02 89 #define NEW_U 0x01 90 91 /* reserved, special-case values of above */ 92 #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */ 93 #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */ 94 #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U) 95 96 #define TCP_PUSH_BIT 0x10 97 98 99 /* 100 * "state" data for each active tcp conversation on the wire. This is 101 * basically a copy of the entire IP/TCP header from the last packet 102 * we saw from the conversation together with a small identifier 103 * the transmit & receive ends of the line use to locate saved header. 104 */ 105 struct cstate { 106 struct cstate *cs_next; /* next most recently used state (xmit only) */ 107 u_short cs_hlen; /* size of hdr (receive only) */ 108 u_char cs_id; /* connection # associated with this state */ 109 u_char cs_filler; 110 union { 111 char csu_hdr[MAX_HDR]; 112 struct ip_hdr csu_ip; /* ip/tcp hdr from most recent packet */ 113 } vjcs_u; 114 }; 115 #define cs_ip vjcs_u.csu_ip 116 #define cs_hdr vjcs_u.csu_hdr 117 118 119 struct vjstat { 120 unsigned long vjs_packets; /* outbound packets */ 121 unsigned long vjs_compressed; /* outbound compressed packets */ 122 unsigned long vjs_searches; /* searches for connection state */ 123 unsigned long vjs_misses; /* times couldn't find conn. state */ 124 unsigned long vjs_uncompressedin; /* inbound uncompressed packets */ 125 unsigned long vjs_compressedin; /* inbound compressed packets */ 126 unsigned long vjs_errorin; /* inbound unknown type packets */ 127 unsigned long vjs_tossed; /* inbound packets tossed because of error */ 128 }; 129 130 /* 131 * all the state data for one serial line (we need one of these per line). 132 */ 133 struct vjcompress { 134 struct cstate *last_cs; /* most recently used tstate */ 135 u_char last_recv; /* last rcvd conn. id */ 136 u_char last_xmit; /* last sent conn. id */ 137 u_short flags; 138 u_char maxSlotIndex; 139 u_char compressSlot; /* Flag indicating OK to compress slot ID. */ 140 #if LINK_STATS 141 struct vjstat stats; 142 #endif 143 struct cstate tstate[MAX_SLOTS]; /* xmit connection states */ 144 struct cstate rstate[MAX_SLOTS]; /* receive connection states */ 145 }; 146 147 /* flag values */ 148 #define VJF_TOSS 1U /* tossing rcvd frames because of input err */ 149 150 extern void vj_compress_init (struct vjcompress *comp); 151 extern u_int vj_compress_tcp (struct vjcompress *comp, struct pbuf *pb); 152 extern void vj_uncompress_err (struct vjcompress *comp); 153 extern int vj_uncompress_uncomp(struct pbuf *nb, struct vjcompress *comp); 154 extern int vj_uncompress_tcp (struct pbuf **nb, struct vjcompress *comp); 155 156 #endif /* VJ_H */ 157
