1 | #include <machine/rtems-bsd-kernel-space.h> |
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2 | |
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3 | /* |
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4 | * alias_pptp.c |
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5 | * |
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6 | * Copyright (c) 2000 Whistle Communications, Inc. |
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7 | * All rights reserved. |
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8 | * |
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9 | * Subject to the following obligations and disclaimer of warranty, use and |
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10 | * redistribution of this software, in source or object code forms, with or |
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11 | * without modifications are expressly permitted by Whistle Communications; |
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12 | * provided, however, that: |
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13 | * 1. Any and all reproductions of the source or object code must include the |
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14 | * copyright notice above and the following disclaimer of warranties; and |
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15 | * 2. No rights are granted, in any manner or form, to use Whistle |
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16 | * Communications, Inc. trademarks, including the mark "WHISTLE |
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17 | * COMMUNICATIONS" on advertising, endorsements, or otherwise except as |
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18 | * such appears in the above copyright notice or in the software. |
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19 | * |
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20 | * THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND |
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21 | * TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO |
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22 | * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE, |
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23 | * INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF |
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24 | * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. |
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25 | * WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY |
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26 | * REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS |
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27 | * SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE. |
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28 | * IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES |
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29 | * RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING |
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30 | * WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, |
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31 | * PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR |
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32 | * SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY |
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33 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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34 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
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35 | * THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY |
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36 | * OF SUCH DAMAGE. |
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37 | * |
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38 | * Author: Erik Salander <erik@whistle.com> |
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39 | */ |
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40 | |
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41 | #include <sys/cdefs.h> |
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42 | __FBSDID("$FreeBSD$"); |
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43 | |
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44 | /* Includes */ |
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45 | #ifdef _KERNEL |
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46 | #include <rtems/bsd/sys/param.h> |
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47 | #include <sys/limits.h> |
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48 | #include <sys/kernel.h> |
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49 | #include <sys/module.h> |
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50 | #else |
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51 | #include <errno.h> |
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52 | #include <limits.h> |
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53 | #include <rtems/bsd/sys/types.h> |
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54 | #include <stdio.h> |
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55 | #endif |
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56 | |
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57 | #include <netinet/tcp.h> |
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58 | |
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59 | #ifdef _KERNEL |
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60 | #include <netinet/libalias/alias.h> |
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61 | #include <netinet/libalias/alias_local.h> |
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62 | #include <netinet/libalias/alias_mod.h> |
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63 | #else |
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64 | #include "alias.h" |
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65 | #include "alias_local.h" |
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66 | #include "alias_mod.h" |
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67 | #endif |
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68 | |
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69 | #define PPTP_CONTROL_PORT_NUMBER 1723 |
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70 | |
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71 | static void |
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72 | AliasHandlePptpOut(struct libalias *, struct ip *, struct alias_link *); |
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73 | |
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74 | static void |
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75 | AliasHandlePptpIn(struct libalias *, struct ip *, struct alias_link *); |
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76 | |
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77 | static int |
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78 | AliasHandlePptpGreOut(struct libalias *, struct ip *); |
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79 | |
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80 | static int |
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81 | AliasHandlePptpGreIn(struct libalias *, struct ip *); |
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82 | |
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83 | static int |
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84 | fingerprint(struct libalias *la, struct alias_data *ah) |
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85 | { |
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86 | |
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87 | if (ah->dport == NULL || ah->sport == NULL || ah->lnk == NULL) |
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88 | return (-1); |
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89 | if (ntohs(*ah->dport) == PPTP_CONTROL_PORT_NUMBER |
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90 | || ntohs(*ah->sport) == PPTP_CONTROL_PORT_NUMBER) |
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91 | return (0); |
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92 | return (-1); |
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93 | } |
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94 | |
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95 | static int |
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96 | fingerprintgre(struct libalias *la, struct alias_data *ah) |
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97 | { |
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98 | |
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99 | return (0); |
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100 | } |
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101 | |
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102 | static int |
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103 | protohandlerin(struct libalias *la, struct ip *pip, struct alias_data *ah) |
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104 | { |
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105 | |
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106 | AliasHandlePptpIn(la, pip, ah->lnk); |
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107 | return (0); |
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108 | } |
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109 | |
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110 | static int |
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111 | protohandlerout(struct libalias *la, struct ip *pip, struct alias_data *ah) |
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112 | { |
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113 | |
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114 | AliasHandlePptpOut(la, pip, ah->lnk); |
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115 | return (0); |
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116 | } |
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117 | |
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118 | static int |
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119 | protohandlergrein(struct libalias *la, struct ip *pip, struct alias_data *ah) |
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120 | { |
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121 | |
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122 | if (la->packetAliasMode & PKT_ALIAS_PROXY_ONLY || |
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123 | AliasHandlePptpGreIn(la, pip) == 0) |
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124 | return (0); |
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125 | return (-1); |
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126 | } |
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127 | |
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128 | static int |
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129 | protohandlergreout(struct libalias *la, struct ip *pip, struct alias_data *ah) |
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130 | { |
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131 | |
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132 | if (AliasHandlePptpGreOut(la, pip) == 0) |
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133 | return (0); |
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134 | return (-1); |
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135 | } |
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136 | |
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137 | /* Kernel module definition. */ |
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138 | struct proto_handler handlers[] = { |
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139 | { |
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140 | .pri = 200, |
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141 | .dir = IN, |
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142 | .proto = TCP, |
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143 | .fingerprint = &fingerprint, |
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144 | .protohandler = &protohandlerin |
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145 | }, |
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146 | { |
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147 | .pri = 210, |
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148 | .dir = OUT, |
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149 | .proto = TCP, |
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150 | .fingerprint = &fingerprint, |
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151 | .protohandler = &protohandlerout |
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152 | }, |
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153 | /* |
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154 | * WATCH OUT!!! these 2 handlers NEED a priority of INT_MAX (highest possible) |
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155 | * cause they will ALWAYS process packets, so they must be the last one |
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156 | * in chain: look fingerprintgre() above. |
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157 | */ |
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158 | { |
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159 | .pri = INT_MAX, |
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160 | .dir = IN, |
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161 | .proto = IP, |
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162 | .fingerprint = &fingerprintgre, |
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163 | .protohandler = &protohandlergrein |
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164 | }, |
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165 | { |
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166 | .pri = INT_MAX, |
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167 | .dir = OUT, |
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168 | .proto = IP, |
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169 | .fingerprint = &fingerprintgre, |
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170 | .protohandler = &protohandlergreout |
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171 | }, |
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172 | { EOH } |
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173 | }; |
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174 | static int |
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175 | mod_handler(module_t mod, int type, void *data) |
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176 | { |
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177 | int error; |
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178 | |
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179 | switch (type) { |
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180 | case MOD_LOAD: |
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181 | error = 0; |
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182 | LibAliasAttachHandlers(handlers); |
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183 | break; |
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184 | case MOD_UNLOAD: |
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185 | error = 0; |
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186 | LibAliasDetachHandlers(handlers); |
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187 | break; |
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188 | default: |
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189 | error = EINVAL; |
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190 | } |
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191 | return (error); |
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192 | } |
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193 | |
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194 | #ifdef _KERNEL |
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195 | static |
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196 | #endif |
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197 | moduledata_t alias_mod = { |
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198 | "alias_pptp", mod_handler, NULL |
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199 | }; |
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200 | |
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201 | #ifdef _KERNEL |
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202 | DECLARE_MODULE(alias_pptp, alias_mod, SI_SUB_DRIVERS, SI_ORDER_SECOND); |
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203 | MODULE_VERSION(alias_pptp, 1); |
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204 | MODULE_DEPEND(alias_pptp, libalias, 1, 1, 1); |
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205 | #endif |
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206 | |
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207 | /* |
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208 | Alias_pptp.c performs special processing for PPTP sessions under TCP. |
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209 | Specifically, watch PPTP control messages and alias the Call ID or the |
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210 | Peer's Call ID in the appropriate messages. Note, PPTP requires |
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211 | "de-aliasing" of incoming packets, this is different than any other |
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212 | TCP applications that are currently (ie. FTP, IRC and RTSP) aliased. |
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213 | |
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214 | For Call IDs encountered for the first time, a PPTP alias link is created. |
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215 | The PPTP alias link uses the Call ID in place of the original port number. |
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216 | An alias Call ID is created. |
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217 | |
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218 | For this routine to work, the PPTP control messages must fit entirely |
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219 | into a single TCP packet. This is typically the case, but is not |
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220 | required by the spec. |
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221 | |
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222 | Unlike some of the other TCP applications that are aliased (ie. FTP, |
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223 | IRC and RTSP), the PPTP control messages that need to be aliased are |
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224 | guaranteed to remain the same length. The aliased Call ID is a fixed |
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225 | length field. |
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226 | |
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227 | Reference: RFC 2637 |
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228 | |
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229 | Initial version: May, 2000 (eds) |
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230 | |
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231 | */ |
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232 | |
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233 | /* |
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234 | * PPTP definitions |
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235 | */ |
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236 | |
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237 | struct grehdr { /* Enhanced GRE header. */ |
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238 | u_int16_t gh_flags; /* Flags. */ |
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239 | u_int16_t gh_protocol; /* Protocol type. */ |
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240 | u_int16_t gh_length; /* Payload length. */ |
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241 | u_int16_t gh_call_id; /* Call ID. */ |
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242 | u_int32_t gh_seq_no; /* Sequence number (optional). */ |
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243 | u_int32_t gh_ack_no; /* Acknowledgment number |
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244 | * (optional). */ |
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245 | }; |
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246 | typedef struct grehdr GreHdr; |
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247 | |
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248 | /* The PPTP protocol ID used in the GRE 'proto' field. */ |
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249 | #define PPTP_GRE_PROTO 0x880b |
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250 | |
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251 | /* Bits that must be set a certain way in all PPTP/GRE packets. */ |
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252 | #define PPTP_INIT_VALUE ((0x2001 << 16) | PPTP_GRE_PROTO) |
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253 | #define PPTP_INIT_MASK 0xef7fffff |
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254 | |
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255 | #define PPTP_MAGIC 0x1a2b3c4d |
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256 | #define PPTP_CTRL_MSG_TYPE 1 |
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257 | |
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258 | enum { |
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259 | PPTP_StartCtrlConnRequest = 1, |
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260 | PPTP_StartCtrlConnReply = 2, |
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261 | PPTP_StopCtrlConnRequest = 3, |
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262 | PPTP_StopCtrlConnReply = 4, |
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263 | PPTP_EchoRequest = 5, |
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264 | PPTP_EchoReply = 6, |
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265 | PPTP_OutCallRequest = 7, |
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266 | PPTP_OutCallReply = 8, |
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267 | PPTP_InCallRequest = 9, |
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268 | PPTP_InCallReply = 10, |
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269 | PPTP_InCallConn = 11, |
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270 | PPTP_CallClearRequest = 12, |
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271 | PPTP_CallDiscNotify = 13, |
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272 | PPTP_WanErrorNotify = 14, |
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273 | PPTP_SetLinkInfo = 15 |
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274 | }; |
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275 | |
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276 | /* Message structures */ |
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277 | struct pptpMsgHead { |
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278 | u_int16_t length; /* total length */ |
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279 | u_int16_t msgType;/* PPTP message type */ |
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280 | u_int32_t magic; /* magic cookie */ |
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281 | u_int16_t type; /* control message type */ |
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282 | u_int16_t resv0; /* reserved */ |
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283 | }; |
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284 | typedef struct pptpMsgHead *PptpMsgHead; |
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285 | |
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286 | struct pptpCodes { |
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287 | u_int8_t resCode;/* Result Code */ |
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288 | u_int8_t errCode;/* Error Code */ |
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289 | }; |
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290 | typedef struct pptpCodes *PptpCode; |
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291 | |
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292 | struct pptpCallIds { |
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293 | u_int16_t cid1; /* Call ID field #1 */ |
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294 | u_int16_t cid2; /* Call ID field #2 */ |
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295 | }; |
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296 | typedef struct pptpCallIds *PptpCallId; |
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297 | |
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298 | static PptpCallId AliasVerifyPptp(struct ip *, u_int16_t *); |
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299 | |
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300 | |
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301 | static void |
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302 | AliasHandlePptpOut(struct libalias *la, |
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303 | struct ip *pip, /* IP packet to examine/patch */ |
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304 | struct alias_link *lnk) |
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305 | { /* The PPTP control link */ |
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306 | struct alias_link *pptp_lnk; |
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307 | PptpCallId cptr; |
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308 | PptpCode codes; |
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309 | u_int16_t ctl_type; /* control message type */ |
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310 | struct tcphdr *tc; |
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311 | |
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312 | /* Verify valid PPTP control message */ |
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313 | if ((cptr = AliasVerifyPptp(pip, &ctl_type)) == NULL) |
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314 | return; |
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315 | |
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316 | /* Modify certain PPTP messages */ |
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317 | switch (ctl_type) { |
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318 | case PPTP_OutCallRequest: |
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319 | case PPTP_OutCallReply: |
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320 | case PPTP_InCallRequest: |
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321 | case PPTP_InCallReply: |
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322 | /* |
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323 | * Establish PPTP link for address and Call ID found in |
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324 | * control message. |
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325 | */ |
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326 | pptp_lnk = AddPptp(la, GetOriginalAddress(lnk), GetDestAddress(lnk), |
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327 | GetAliasAddress(lnk), cptr->cid1); |
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328 | break; |
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329 | case PPTP_CallClearRequest: |
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330 | case PPTP_CallDiscNotify: |
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331 | /* |
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332 | * Find PPTP link for address and Call ID found in control |
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333 | * message. |
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334 | */ |
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335 | pptp_lnk = FindPptpOutByCallId(la, GetOriginalAddress(lnk), |
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336 | GetDestAddress(lnk), |
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337 | cptr->cid1); |
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338 | break; |
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339 | default: |
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340 | return; |
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341 | } |
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342 | |
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343 | if (pptp_lnk != NULL) { |
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344 | int accumulate = cptr->cid1; |
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345 | |
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346 | /* alias the Call Id */ |
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347 | cptr->cid1 = GetAliasPort(pptp_lnk); |
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348 | |
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349 | /* Compute TCP checksum for revised packet */ |
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350 | tc = (struct tcphdr *)ip_next(pip); |
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351 | accumulate -= cptr->cid1; |
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352 | ADJUST_CHECKSUM(accumulate, tc->th_sum); |
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353 | |
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354 | switch (ctl_type) { |
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355 | case PPTP_OutCallReply: |
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356 | case PPTP_InCallReply: |
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357 | codes = (PptpCode) (cptr + 1); |
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358 | if (codes->resCode == 1) /* Connection |
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359 | * established, */ |
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360 | SetDestCallId(pptp_lnk, /* note the Peer's Call |
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361 | * ID. */ |
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362 | cptr->cid2); |
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363 | else |
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364 | SetExpire(pptp_lnk, 0); /* Connection refused. */ |
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365 | break; |
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366 | case PPTP_CallDiscNotify: /* Connection closed. */ |
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367 | SetExpire(pptp_lnk, 0); |
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368 | break; |
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369 | } |
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370 | } |
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371 | } |
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372 | |
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373 | static void |
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374 | AliasHandlePptpIn(struct libalias *la, |
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375 | struct ip *pip, /* IP packet to examine/patch */ |
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376 | struct alias_link *lnk) |
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377 | { /* The PPTP control link */ |
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378 | struct alias_link *pptp_lnk; |
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379 | PptpCallId cptr; |
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380 | u_int16_t *pcall_id; |
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381 | u_int16_t ctl_type; /* control message type */ |
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382 | struct tcphdr *tc; |
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383 | |
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384 | /* Verify valid PPTP control message */ |
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385 | if ((cptr = AliasVerifyPptp(pip, &ctl_type)) == NULL) |
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386 | return; |
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387 | |
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388 | /* Modify certain PPTP messages */ |
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389 | switch (ctl_type) { |
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390 | case PPTP_InCallConn: |
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391 | case PPTP_WanErrorNotify: |
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392 | case PPTP_SetLinkInfo: |
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393 | pcall_id = &cptr->cid1; |
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394 | break; |
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395 | case PPTP_OutCallReply: |
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396 | case PPTP_InCallReply: |
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397 | pcall_id = &cptr->cid2; |
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398 | break; |
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399 | case PPTP_CallDiscNotify: /* Connection closed. */ |
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400 | pptp_lnk = FindPptpInByCallId(la, GetDestAddress(lnk), |
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401 | GetAliasAddress(lnk), |
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402 | cptr->cid1); |
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403 | if (pptp_lnk != NULL) |
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404 | SetExpire(pptp_lnk, 0); |
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405 | return; |
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406 | default: |
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407 | return; |
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408 | } |
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409 | |
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410 | /* Find PPTP link for address and Call ID found in PPTP Control Msg */ |
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411 | pptp_lnk = FindPptpInByPeerCallId(la, GetDestAddress(lnk), |
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412 | GetAliasAddress(lnk), |
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413 | *pcall_id); |
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414 | |
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415 | if (pptp_lnk != NULL) { |
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416 | int accumulate = *pcall_id; |
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417 | |
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418 | /* De-alias the Peer's Call Id. */ |
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419 | *pcall_id = GetOriginalPort(pptp_lnk); |
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420 | |
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421 | /* Compute TCP checksum for modified packet */ |
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422 | tc = (struct tcphdr *)ip_next(pip); |
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423 | accumulate -= *pcall_id; |
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424 | ADJUST_CHECKSUM(accumulate, tc->th_sum); |
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425 | |
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426 | if (ctl_type == PPTP_OutCallReply || ctl_type == PPTP_InCallReply) { |
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427 | PptpCode codes = (PptpCode) (cptr + 1); |
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428 | |
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429 | if (codes->resCode == 1) /* Connection |
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430 | * established, */ |
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431 | SetDestCallId(pptp_lnk, /* note the Call ID. */ |
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432 | cptr->cid1); |
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433 | else |
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434 | SetExpire(pptp_lnk, 0); /* Connection refused. */ |
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435 | } |
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436 | } |
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437 | } |
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438 | |
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439 | static PptpCallId |
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440 | AliasVerifyPptp(struct ip *pip, u_int16_t * ptype) |
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441 | { /* IP packet to examine/patch */ |
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442 | int hlen, tlen, dlen; |
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443 | PptpMsgHead hptr; |
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444 | struct tcphdr *tc; |
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445 | |
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446 | /* Calculate some lengths */ |
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447 | tc = (struct tcphdr *)ip_next(pip); |
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448 | hlen = (pip->ip_hl + tc->th_off) << 2; |
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449 | tlen = ntohs(pip->ip_len); |
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450 | dlen = tlen - hlen; |
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451 | |
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452 | /* Verify data length */ |
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453 | if (dlen < (int)(sizeof(struct pptpMsgHead) + sizeof(struct pptpCallIds))) |
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454 | return (NULL); |
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455 | |
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456 | /* Move up to PPTP message header */ |
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457 | hptr = (PptpMsgHead) tcp_next(tc); |
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458 | |
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459 | /* Return the control message type */ |
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460 | *ptype = ntohs(hptr->type); |
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461 | |
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462 | /* Verify PPTP Control Message */ |
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463 | if ((ntohs(hptr->msgType) != PPTP_CTRL_MSG_TYPE) || |
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464 | (ntohl(hptr->magic) != PPTP_MAGIC)) |
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465 | return (NULL); |
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466 | |
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467 | /* Verify data length. */ |
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468 | if ((*ptype == PPTP_OutCallReply || *ptype == PPTP_InCallReply) && |
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469 | (dlen < (int)(sizeof(struct pptpMsgHead) + sizeof(struct pptpCallIds) + |
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470 | sizeof(struct pptpCodes)))) |
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471 | return (NULL); |
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472 | else |
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473 | return (PptpCallId) (hptr + 1); |
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474 | } |
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475 | |
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476 | static int |
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477 | AliasHandlePptpGreOut(struct libalias *la, struct ip *pip) |
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478 | { |
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479 | GreHdr *gr; |
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480 | struct alias_link *lnk; |
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481 | |
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482 | gr = (GreHdr *) ip_next(pip); |
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483 | |
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484 | /* Check GRE header bits. */ |
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485 | if ((ntohl(*((u_int32_t *) gr)) & PPTP_INIT_MASK) != PPTP_INIT_VALUE) |
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486 | return (-1); |
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487 | |
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488 | lnk = FindPptpOutByPeerCallId(la, pip->ip_src, pip->ip_dst, gr->gh_call_id); |
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489 | if (lnk != NULL) { |
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490 | struct in_addr alias_addr = GetAliasAddress(lnk); |
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491 | |
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492 | /* Change source IP address. */ |
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493 | DifferentialChecksum(&pip->ip_sum, |
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494 | &alias_addr, &pip->ip_src, 2); |
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495 | pip->ip_src = alias_addr; |
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496 | } |
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497 | return (0); |
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498 | } |
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499 | |
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500 | static int |
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501 | AliasHandlePptpGreIn(struct libalias *la, struct ip *pip) |
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502 | { |
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503 | GreHdr *gr; |
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504 | struct alias_link *lnk; |
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505 | |
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506 | gr = (GreHdr *) ip_next(pip); |
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507 | |
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508 | /* Check GRE header bits. */ |
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509 | if ((ntohl(*((u_int32_t *) gr)) & PPTP_INIT_MASK) != PPTP_INIT_VALUE) |
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510 | return (-1); |
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511 | |
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512 | lnk = FindPptpInByPeerCallId(la, pip->ip_src, pip->ip_dst, gr->gh_call_id); |
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513 | if (lnk != NULL) { |
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514 | struct in_addr src_addr = GetOriginalAddress(lnk); |
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515 | |
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516 | /* De-alias the Peer's Call Id. */ |
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517 | gr->gh_call_id = GetOriginalPort(lnk); |
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518 | |
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519 | /* Restore original IP address. */ |
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520 | DifferentialChecksum(&pip->ip_sum, |
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521 | &src_addr, &pip->ip_dst, 2); |
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522 | pip->ip_dst = src_addr; |
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523 | } |
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524 | return (0); |
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525 | } |
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