[164] | 1 | /*
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| 2 | * Definitions for tcp compression routines.
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| 3 | *
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| 4 | * $Id: vj.h 164 2016-03-07 11:33:50Z coas-nagasima $
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| 5 | *
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| 6 | * Copyright (c) 1989 Regents of the University of California.
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| 7 | * All rights reserved.
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| 8 | *
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| 9 | * Redistribution and use in source and binary forms are permitted
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| 10 | * provided that the above copyright notice and this paragraph are
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| 11 | * duplicated in all such forms and that any documentation,
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| 12 | * advertising materials, and other materials related to such
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| 13 | * distribution and use acknowledge that the software was developed
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| 14 | * by the University of California, Berkeley. The name of the
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| 15 | * University may not be used to endorse or promote products derived
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| 16 | * from this software without specific prior written permission.
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| 17 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
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| 18 | * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
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| 19 | * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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| 20 | *
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| 21 | * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
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| 22 | * - Initial distribution.
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| 23 | */
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| 24 |
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| 25 | #ifndef VJ_H
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| 26 | #define VJ_H
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| 27 |
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| 28 | #include "lwip/ip.h"
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| 29 | #include "lwip/tcp_impl.h"
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| 30 |
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| 31 | #define MAX_SLOTS 16 /* must be > 2 and < 256 */
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| 32 | #define MAX_HDR 128
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| 33 |
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| 34 | /*
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| 35 | * Compressed packet format:
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| 36 | *
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| 37 | * The first octet contains the packet type (top 3 bits), TCP
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| 38 | * 'push' bit, and flags that indicate which of the 4 TCP sequence
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| 39 | * numbers have changed (bottom 5 bits). The next octet is a
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| 40 | * conversation number that associates a saved IP/TCP header with
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| 41 | * the compressed packet. The next two octets are the TCP checksum
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| 42 | * from the original datagram. The next 0 to 15 octets are
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| 43 | * sequence number changes, one change per bit set in the header
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| 44 | * (there may be no changes and there are two special cases where
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| 45 | * the receiver implicitly knows what changed -- see below).
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| 46 | *
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| 47 | * There are 5 numbers which can change (they are always inserted
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| 48 | * in the following order): TCP urgent pointer, window,
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| 49 | * acknowlegement, sequence number and IP ID. (The urgent pointer
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| 50 | * is different from the others in that its value is sent, not the
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| 51 | * change in value.) Since typical use of SLIP links is biased
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| 52 | * toward small packets (see comments on MTU/MSS below), changes
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| 53 | * use a variable length coding with one octet for numbers in the
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| 54 | * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
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| 55 | * range 256 - 65535 or 0. (If the change in sequence number or
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| 56 | * ack is more than 65535, an uncompressed packet is sent.)
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| 57 | */
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| 58 |
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| 59 | /*
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| 60 | * Packet types (must not conflict with IP protocol version)
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| 61 | *
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| 62 | * The top nibble of the first octet is the packet type. There are
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| 63 | * three possible types: IP (not proto TCP or tcp with one of the
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| 64 | * control flags set); uncompressed TCP (a normal IP/TCP packet but
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| 65 | * with the 8-bit protocol field replaced by an 8-bit connection id --
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| 66 | * this type of packet syncs the sender & receiver); and compressed
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| 67 | * TCP (described above).
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| 68 | *
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| 69 | * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
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| 70 | * is logically part of the 4-bit "changes" field that follows. Top
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| 71 | * three bits are actual packet type. For backward compatibility
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| 72 | * and in the interest of conserving bits, numbers are chosen so the
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| 73 | * IP protocol version number (4) which normally appears in this nibble
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| 74 | * means "IP packet".
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| 75 | */
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| 76 |
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| 77 | /* packet types */
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| 78 | #define TYPE_IP 0x40
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| 79 | #define TYPE_UNCOMPRESSED_TCP 0x70
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| 80 | #define TYPE_COMPRESSED_TCP 0x80
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| 81 | #define TYPE_ERROR 0x00
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| 82 |
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| 83 | /* Bits in first octet of compressed packet */
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| 84 | #define NEW_C 0x40 /* flag bits for what changed in a packet */
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| 85 | #define NEW_I 0x20
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| 86 | #define NEW_S 0x08
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| 87 | #define NEW_A 0x04
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| 88 | #define NEW_W 0x02
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| 89 | #define NEW_U 0x01
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| 90 |
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| 91 | /* reserved, special-case values of above */
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| 92 | #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */
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| 93 | #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */
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| 94 | #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U)
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| 95 |
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| 96 | #define TCP_PUSH_BIT 0x10
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| 97 |
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| 98 |
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| 99 | /*
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| 100 | * "state" data for each active tcp conversation on the wire. This is
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| 101 | * basically a copy of the entire IP/TCP header from the last packet
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| 102 | * we saw from the conversation together with a small identifier
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| 103 | * the transmit & receive ends of the line use to locate saved header.
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| 104 | */
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| 105 | struct cstate {
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| 106 | struct cstate *cs_next; /* next most recently used state (xmit only) */
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| 107 | u_short cs_hlen; /* size of hdr (receive only) */
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| 108 | u_char cs_id; /* connection # associated with this state */
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| 109 | u_char cs_filler;
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| 110 | union {
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| 111 | char csu_hdr[MAX_HDR];
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| 112 | struct ip_hdr csu_ip; /* ip/tcp hdr from most recent packet */
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| 113 | } vjcs_u;
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| 114 | };
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| 115 | #define cs_ip vjcs_u.csu_ip
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| 116 | #define cs_hdr vjcs_u.csu_hdr
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| 117 |
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| 118 |
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| 119 | struct vjstat {
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| 120 | unsigned long vjs_packets; /* outbound packets */
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| 121 | unsigned long vjs_compressed; /* outbound compressed packets */
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| 122 | unsigned long vjs_searches; /* searches for connection state */
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| 123 | unsigned long vjs_misses; /* times couldn't find conn. state */
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| 124 | unsigned long vjs_uncompressedin; /* inbound uncompressed packets */
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| 125 | unsigned long vjs_compressedin; /* inbound compressed packets */
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| 126 | unsigned long vjs_errorin; /* inbound unknown type packets */
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| 127 | unsigned long vjs_tossed; /* inbound packets tossed because of error */
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| 128 | };
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| 129 |
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| 130 | /*
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| 131 | * all the state data for one serial line (we need one of these per line).
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| 132 | */
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| 133 | struct vjcompress {
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| 134 | struct cstate *last_cs; /* most recently used tstate */
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| 135 | u_char last_recv; /* last rcvd conn. id */
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| 136 | u_char last_xmit; /* last sent conn. id */
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| 137 | u_short flags;
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| 138 | u_char maxSlotIndex;
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| 139 | u_char compressSlot; /* Flag indicating OK to compress slot ID. */
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| 140 | #if LINK_STATS
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| 141 | struct vjstat stats;
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| 142 | #endif
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| 143 | struct cstate tstate[MAX_SLOTS]; /* xmit connection states */
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| 144 | struct cstate rstate[MAX_SLOTS]; /* receive connection states */
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| 145 | };
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| 146 |
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| 147 | /* flag values */
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| 148 | #define VJF_TOSS 1U /* tossing rcvd frames because of input err */
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| 149 |
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| 150 | extern void vj_compress_init (struct vjcompress *comp);
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| 151 | extern u_int vj_compress_tcp (struct vjcompress *comp, struct pbuf *pb);
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| 152 | extern void vj_uncompress_err (struct vjcompress *comp);
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| 153 | extern int vj_uncompress_uncomp(struct pbuf *nb, struct vjcompress *comp);
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| 154 | extern int vj_uncompress_tcp (struct pbuf **nb, struct vjcompress *comp);
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| 155 |
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| 156 | #endif /* VJ_H */
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