1 | /*
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2 | * Definitions for tcp compression routines.
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3 | *
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4 | * $Id: vj.h 167 2016-03-08 11:37:45Z 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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