1 | /* |
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2 | * Definitions for tcp compression routines. |
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3 | * |
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4 | * Copyright (c) 1989, 1993 |
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5 | * The Regents of the University of California. All rights reserved. |
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6 | * |
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7 | * Redistribution and use in source and binary forms, with or without |
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8 | * modification, are permitted provided that the following conditions |
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9 | * are met: |
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10 | * 1. Redistributions of source code must retain the above copyright |
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11 | * notice, this list of conditions and the following disclaimer. |
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12 | * 2. Redistributions in binary form must reproduce the above copyright |
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13 | * notice, this list of conditions and the following disclaimer in the |
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14 | * documentation and/or other materials provided with the distribution. |
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15 | * 4. Neither the name of the University nor the names of its contributors |
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16 | * may be used to endorse or promote products derived from this software |
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17 | * without specific prior written permission. |
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18 | * |
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19 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
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20 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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21 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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22 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
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23 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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24 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
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25 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
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26 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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27 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
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28 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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29 | * SUCH DAMAGE. |
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30 | * |
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31 | * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989: |
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32 | * - Initial distribution. |
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33 | * $FreeBSD: src/sys/net/slcompress.h,v 1.18 2004/04/07 20:46:12 imp Exp $ |
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34 | */ |
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35 | |
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36 | #ifndef _NET_SLCOMPRESS_H_ |
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37 | #define _NET_SLCOMPRESS_H_ |
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38 | |
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39 | #define MAX_STATES 16 /* must be > 2 and < 256 */ |
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40 | #define MAX_HDR 128 |
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41 | |
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42 | /* |
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43 | * Compressed packet format: |
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44 | * |
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45 | * The first octet contains the packet type (top 3 bits), TCP |
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46 | * 'push' bit, and flags that indicate which of the 4 TCP sequence |
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47 | * numbers have changed (bottom 5 bits). The next octet is a |
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48 | * conversation number that associates a saved IP/TCP header with |
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49 | * the compressed packet. The next two octets are the TCP checksum |
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50 | * from the original datagram. The next 0 to 15 octets are |
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51 | * sequence number changes, one change per bit set in the header |
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52 | * (there may be no changes and there are two special cases where |
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53 | * the receiver implicitly knows what changed -- see below). |
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54 | * |
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55 | * There are 5 numbers which can change (they are always inserted |
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56 | * in the following order): TCP urgent pointer, window, |
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57 | * acknowledgement, sequence number and IP ID. (The urgent pointer |
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58 | * is different from the others in that its value is sent, not the |
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59 | * change in value.) Since typical use of SLIP links is biased |
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60 | * toward small packets (see comments on MTU/MSS below), changes |
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61 | * use a variable length coding with one octet for numbers in the |
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62 | * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the |
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63 | * range 256 - 65535 or 0. (If the change in sequence number or |
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64 | * ack is more than 65535, an uncompressed packet is sent.) |
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65 | */ |
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66 | |
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67 | /* |
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68 | * Packet types (must not conflict with IP protocol version) |
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69 | * |
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70 | * The top nibble of the first octet is the packet type. There are |
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71 | * three possible types: IP (not proto TCP or tcp with one of the |
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72 | * control flags set); uncompressed TCP (a normal IP/TCP packet but |
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73 | * with the 8-bit protocol field replaced by an 8-bit connection id -- |
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74 | * this type of packet syncs the sender & receiver); and compressed |
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75 | * TCP (described above). |
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76 | * |
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77 | * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and |
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78 | * is logically part of the 4-bit "changes" field that follows. Top |
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79 | * three bits are actual packet type. For backward compatibility |
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80 | * and in the interest of conserving bits, numbers are chosen so the |
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81 | * IP protocol version number (4) which normally appears in this nibble |
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82 | * means "IP packet". |
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83 | */ |
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84 | |
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85 | /* packet types */ |
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86 | #define TYPE_IP 0x40 |
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87 | #define TYPE_UNCOMPRESSED_TCP 0x70 |
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88 | #define TYPE_COMPRESSED_TCP 0x80 |
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89 | #define TYPE_ERROR 0x00 |
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90 | |
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91 | /* Bits in first octet of compressed packet */ |
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92 | #define NEW_C 0x40 /* flag bits for what changed in a packet */ |
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93 | #define NEW_I 0x20 |
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94 | #define NEW_S 0x08 |
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95 | #define NEW_A 0x04 |
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96 | #define NEW_W 0x02 |
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97 | #define NEW_U 0x01 |
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98 | |
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99 | /* reserved, special-case values of above */ |
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100 | #define SPECIAL_I (NEW_S|NEW_W|NEW_U) /* echoed interactive traffic */ |
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101 | #define SPECIAL_D (NEW_S|NEW_A|NEW_W|NEW_U) /* unidirectional data */ |
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102 | #define SPECIALS_MASK (NEW_S|NEW_A|NEW_W|NEW_U) |
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103 | |
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104 | #define TCP_PUSH_BIT 0x10 |
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105 | |
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106 | |
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107 | /* |
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108 | * "state" data for each active tcp conversation on the wire. This is |
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109 | * basically a copy of the entire IP/TCP header from the last packet |
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110 | * we saw from the conversation together with a small identifier |
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111 | * the transmit & receive ends of the line use to locate saved header. |
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112 | */ |
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113 | struct cstate { |
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114 | struct cstate *cs_next; /* next most recently used cstate (xmit only) */ |
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115 | u_int16_t cs_hlen; /* size of hdr (receive only) */ |
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116 | u_char cs_id; /* connection # associated with this state */ |
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117 | u_char cs_filler; |
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118 | union { |
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119 | char csu_hdr[MAX_HDR]; |
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120 | struct ip csu_ip; /* ip/tcp hdr from most recent packet */ |
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121 | } slcs_u; |
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122 | }; |
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123 | #define cs_ip slcs_u.csu_ip |
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124 | #define cs_hdr slcs_u.csu_hdr |
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125 | |
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126 | /* |
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127 | * all the state data for one serial line (we need one of these |
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128 | * per line). |
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129 | */ |
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130 | struct slcompress { |
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131 | struct cstate *last_cs; /* most recently used tstate */ |
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132 | u_char last_recv; /* last rcvd conn. id */ |
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133 | u_char last_xmit; /* last sent conn. id */ |
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134 | u_int16_t flags; |
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135 | #ifndef SL_NO_STATS |
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136 | int sls_packets; /* outbound packets */ |
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137 | int sls_compressed; /* outbound compressed packets */ |
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138 | int sls_searches; /* searches for connection state */ |
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139 | int sls_misses; /* times couldn't find conn. state */ |
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140 | int sls_uncompressedin; /* inbound uncompressed packets */ |
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141 | int sls_compressedin; /* inbound compressed packets */ |
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142 | int sls_errorin; /* inbound unknown type packets */ |
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143 | int sls_tossed; /* inbound packets tossed because of error */ |
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144 | #endif |
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145 | struct cstate tstate[MAX_STATES]; /* xmit connection states */ |
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146 | struct cstate rstate[MAX_STATES]; /* receive connection states */ |
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147 | }; |
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148 | /* flag values */ |
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149 | #define SLF_TOSS 1 /* tossing rcvd frames because of input err */ |
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150 | |
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151 | void sl_compress_init(struct slcompress *, int); |
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152 | u_int sl_compress_tcp(struct mbuf *, struct ip *, struct slcompress *, int); |
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153 | int sl_uncompress_tcp(u_char **, int, u_int, struct slcompress *); |
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154 | int sl_uncompress_tcp_core(u_char *, int, int, u_int, |
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155 | struct slcompress *, u_char **, u_int *); |
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156 | |
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157 | #endif /* !_NET_SLCOMPRESS_H_ */ |
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