Travis Geiselbrecht | 1d0df69 | 2008-09-01 02:26:09 -0700 | [diff] [blame^] | 1 | /* |
| 2 | * Definitions for tcp compression routines. |
| 3 | * |
| 4 | * $Id: vj.h,v 1.4 2004/02/07 00:30:03 likewise 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@helios.ee.lbl.gov), Dec 31, 1989: |
| 22 | * - Initial distribution. |
| 23 | */ |
| 24 | |
| 25 | #ifndef VJ_H |
| 26 | #define VJ_H |
| 27 | |
| 28 | #include "vjbsdhdr.h" |
| 29 | |
| 30 | #define MAX_SLOTS 16 /* must be > 2 and < 256 */ |
| 31 | #define MAX_HDR 128 |
| 32 | |
| 33 | /* |
| 34 | * Compressed packet format: |
| 35 | * |
| 36 | * The first octet contains the packet type (top 3 bits), TCP |
| 37 | * 'push' bit, and flags that indicate which of the 4 TCP sequence |
| 38 | * numbers have changed (bottom 5 bits). The next octet is a |
| 39 | * conversation number that associates a saved IP/TCP header with |
| 40 | * the compressed packet. The next two octets are the TCP checksum |
| 41 | * from the original datagram. The next 0 to 15 octets are |
| 42 | * sequence number changes, one change per bit set in the header |
| 43 | * (there may be no changes and there are two special cases where |
| 44 | * the receiver implicitly knows what changed -- see below). |
| 45 | * |
| 46 | * There are 5 numbers which can change (they are always inserted |
| 47 | * in the following order): TCP urgent pointer, window, |
| 48 | * acknowlegement, sequence number and IP ID. (The urgent pointer |
| 49 | * is different from the others in that its value is sent, not the |
| 50 | * change in value.) Since typical use of SLIP links is biased |
| 51 | * toward small packets (see comments on MTU/MSS below), changes |
| 52 | * use a variable length coding with one octet for numbers in the |
| 53 | * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the |
| 54 | * range 256 - 65535 or 0. (If the change in sequence number or |
| 55 | * ack is more than 65535, an uncompressed packet is sent.) |
| 56 | */ |
| 57 | |
| 58 | /* |
| 59 | * Packet types (must not conflict with IP protocol version) |
| 60 | * |
| 61 | * The top nibble of the first octet is the packet type. There are |
| 62 | * three possible types: IP (not proto TCP or tcp with one of the |
| 63 | * control flags set); uncompressed TCP (a normal IP/TCP packet but |
| 64 | * with the 8-bit protocol field replaced by an 8-bit connection id -- |
| 65 | * this type of packet syncs the sender & receiver); and compressed |
| 66 | * TCP (described above). |
| 67 | * |
| 68 | * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and |
| 69 | * is logically part of the 4-bit "changes" field that follows. Top |
| 70 | * three bits are actual packet type. For backward compatibility |
| 71 | * and in the interest of conserving bits, numbers are chosen so the |
| 72 | * IP protocol version number (4) which normally appears in this nibble |
| 73 | * means "IP packet". |
| 74 | */ |
| 75 | |
| 76 | /* packet types */ |
| 77 | #define TYPE_IP 0x40 |
| 78 | #define TYPE_UNCOMPRESSED_TCP 0x70 |
| 79 | #define TYPE_COMPRESSED_TCP 0x80 |
| 80 | #define TYPE_ERROR 0x00 |
| 81 | |
| 82 | /* Bits in first octet of compressed packet */ |
| 83 | #define NEW_C 0x40 /* flag bits for what changed in a packet */ |
| 84 | #define NEW_I 0x20 |
| 85 | #define NEW_S 0x08 |
| 86 | #define NEW_A 0x04 |
| 87 | #define NEW_W 0x02 |
| 88 | #define NEW_U 0x01 |
| 89 | |
| 90 | /* reserved, special-case values of above */ |
| 91 | #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */ |
| 92 | #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */ |
| 93 | #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U) |
| 94 | |
| 95 | #define TCP_PUSH_BIT 0x10 |
| 96 | |
| 97 | |
| 98 | /* |
| 99 | * "state" data for each active tcp conversation on the wire. This is |
| 100 | * basically a copy of the entire IP/TCP header from the last packet |
| 101 | * we saw from the conversation together with a small identifier |
| 102 | * the transmit & receive ends of the line use to locate saved header. |
| 103 | */ |
| 104 | struct cstate { |
| 105 | struct cstate *cs_next; /* next most recently used state (xmit only) */ |
| 106 | u_short cs_hlen; /* size of hdr (receive only) */ |
| 107 | u_char cs_id; /* connection # associated with this state */ |
| 108 | u_char cs_filler; |
| 109 | union { |
| 110 | char csu_hdr[MAX_HDR]; |
| 111 | struct ip csu_ip; /* ip/tcp hdr from most recent packet */ |
| 112 | } vjcs_u; |
| 113 | }; |
| 114 | #define cs_ip vjcs_u.csu_ip |
| 115 | #define cs_hdr vjcs_u.csu_hdr |
| 116 | |
| 117 | |
| 118 | struct vjstat { |
| 119 | unsigned long vjs_packets; /* outbound packets */ |
| 120 | unsigned long vjs_compressed; /* outbound compressed packets */ |
| 121 | unsigned long vjs_searches; /* searches for connection state */ |
| 122 | unsigned long vjs_misses; /* times couldn't find conn. state */ |
| 123 | unsigned long vjs_uncompressedin; /* inbound uncompressed packets */ |
| 124 | unsigned long vjs_compressedin; /* inbound compressed packets */ |
| 125 | unsigned long vjs_errorin; /* inbound unknown type packets */ |
| 126 | unsigned long vjs_tossed; /* inbound packets tossed because of error */ |
| 127 | }; |
| 128 | |
| 129 | /* |
| 130 | * all the state data for one serial line (we need one of these per line). |
| 131 | */ |
| 132 | struct vjcompress { |
| 133 | struct cstate *last_cs; /* most recently used tstate */ |
| 134 | u_char last_recv; /* last rcvd conn. id */ |
| 135 | u_char last_xmit; /* last sent conn. id */ |
| 136 | u_short flags; |
| 137 | u_char maxSlotIndex; |
| 138 | u_char compressSlot; /* Flag indicating OK to compress slot ID. */ |
| 139 | #if LINK_STATS |
| 140 | struct vjstat stats; |
| 141 | #endif |
| 142 | struct cstate tstate[MAX_SLOTS]; /* xmit connection states */ |
| 143 | struct cstate rstate[MAX_SLOTS]; /* receive connection states */ |
| 144 | }; |
| 145 | |
| 146 | /* flag values */ |
| 147 | #define VJF_TOSS 1U /* tossing rcvd frames because of input err */ |
| 148 | |
| 149 | extern void vj_compress_init (struct vjcompress *comp); |
| 150 | extern u_int vj_compress_tcp (struct vjcompress *comp, struct pbuf *pb); |
| 151 | extern void vj_uncompress_err (struct vjcompress *comp); |
| 152 | extern int vj_uncompress_uncomp(struct pbuf *nb, struct vjcompress *comp); |
| 153 | extern int vj_uncompress_tcp(struct pbuf **nb, struct vjcompress *comp); |
| 154 | |
| 155 | #endif /* VJ_H */ |