1 | /* |
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2 | This program is free software: you can redistribute it and/or modify |
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3 | it under the terms of the GNU General Public License as published by |
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4 | the Free Software Foundation, either version 3 of the License, or |
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5 | (at your option) any later version. |
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6 | |
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7 | This program is distributed in the hope that it will be useful, |
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8 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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9 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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10 | GNU General Public License for more details. |
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11 | |
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12 | You should have received a copy of the GNU General Public License |
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13 | along with this program. If not, see <http://www.gnu.org/licenses/>. |
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14 | */ |
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15 | |
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16 | /* |
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17 | Copyright 2010 Luke Bratch <l_bratch@yahoo.co.uk> |
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18 | |
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19 | UDP header struct and modification method from udp-broadcast-relay [1]. |
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20 | I believe the struct was originally by cs6171@scitsc.wlv.ac.uk. |
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21 | |
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22 | [1] http://www.joachim-breitner.de/udp-broadcast-relay/ |
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23 | */ |
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24 | /* |
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25 | Modificado LCFIB - UPC Daniel Sanchez 2012 |
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26 | |
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27 | Anyadimos la capacidad de enviar mensajes de broadcast a destinatario. Para poder |
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28 | usar esta opcion hay que ser root. |
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29 | Anyadimos funcion debugger |
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30 | |
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31 | */ |
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32 | |
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33 | #include <string.h> |
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34 | #include <arpa/inet.h> |
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35 | #include <stdio.h> |
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36 | #include <linux/if.h> |
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37 | |
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38 | int main(int argc, char *argv[]) { |
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39 | |
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40 | /* Listening and destination ports */ |
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41 | unsigned short int lstport; |
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42 | unsigned short int dstport; |
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43 | |
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44 | /* Receiving and sending sockets */ |
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45 | int rcvfd; |
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46 | int sndfd; |
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47 | |
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48 | /* Destination addresses */ |
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49 | struct { |
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50 | struct sockaddr_in dstaddr; |
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51 | } dsts[argc - 4]; /* Anything after 4th arg is a destination address */ |
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52 | /* Number of destination addresses */ |
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53 | int dstcount; |
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54 | |
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55 | /* Source packet */ |
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56 | struct msghdr rcvmsg; |
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57 | struct iovec iov; |
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58 | u_char pkt_info[16384]; |
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59 | int rcvlen; |
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60 | |
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61 | /* Address of source packet */ |
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62 | struct sockaddr_in srcaddr; |
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63 | |
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64 | /* For for loops */ |
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65 | int i; |
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66 | /* For setsockopt() values */ |
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67 | int optval; |
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68 | /* For debug */ |
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69 | int debug = 0; |
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70 | |
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71 | |
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72 | /* Outgoing UDP packet structure */ |
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73 | u_char packet[4096] = { |
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74 | 0x45, 0x00, 0x00, 0x26, |
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75 | 0x12, 0x34, 0x00, 0x00, |
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76 | 0xFF, 0x11, 0, 0, |
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77 | 0, 0, 0, 0, |
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78 | 0, 0, 0, 0, |
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79 | 0, 0, 0, 0, |
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80 | 0x00, 0x12, 0x00, 0x00, |
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81 | '1','2','3','4','5','6','7','8','9','0' |
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82 | }; |
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83 | |
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84 | /* Print some usage instructions */ |
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85 | if (argc < 5) { |
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86 | fprintf(stderr, "Usage: %s LST-ADDR LST-PORT DST-PORT DST-ADDR [DST-ADDR]...\n" |
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87 | "\n" |
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88 | "bind()s to address LST-ADDR on port LST-PORT and retransmits UDP\n" |
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89 | "packets received to addresses(s) DST-ADDR(s) on port DST-PORT,\n" |
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90 | "with modified headers to reflect the new target.\n" |
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91 | "\n" |
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92 | "To receieve broadcast traffic, use a LST-ADDR of 0.0.0.0. If\n" |
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93 | "a program is already listening on LST-PORT on LST-ADDR, you may\n" |
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94 | "listen on a broadcast address such as 255.255.255.255.\n" |
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95 | "\n" |
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96 | "Steam broadcasts to a number of different ports, so it is\n" |
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97 | "sufficient to listen on a different port to your game server.\n" |
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98 | "e.g. a LST-PORT of 27016 and a DST-PORT of 27015 will let you\n" |
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99 | "listen on a different port to a game server, but for it to still\n" |
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100 | "directly receive packets that were broadcast.\n", |
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101 | argv[0]); |
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102 | return 1; |
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103 | } |
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104 | |
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105 | if (((lstport = atoi(argv[2])) == 0) || ((dstport = atoi(argv[3])) == 0)) { |
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106 | fprintf(stderr, "lst-port or dst-port is invalid\n"); |
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107 | return 1; |
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108 | } |
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109 | |
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110 | /* Populate iovec */ |
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111 | iov.iov_base = packet + 28; /* Header length is 28 */ |
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112 | iov.iov_len = 3977; /* 4006 - header length - 1 */ |
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113 | |
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114 | /* Populate msghdr */ |
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115 | rcvmsg.msg_name = &srcaddr; |
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116 | rcvmsg.msg_namelen = sizeof(srcaddr); |
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117 | rcvmsg.msg_iov = &iov; |
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118 | rcvmsg.msg_iovlen = 1; |
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119 | rcvmsg.msg_control = pkt_info; |
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120 | rcvmsg.msg_controllen = sizeof(pkt_info); |
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121 | |
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122 | /* Enumerate destination addresses */ |
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123 | for (i = 0; i < argc - 4; i++) { |
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124 | dsts[i].dstaddr.sin_family = AF_INET; |
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125 | dsts[i].dstaddr.sin_port = htons(dstport); |
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126 | if ((inet_pton(AF_INET, argv[i + 4], &dsts[i].dstaddr.sin_addr)) != 1) { |
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127 | fprintf(stderr, "dst-addr%d is invalid\n", i + 1); |
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128 | return 1; |
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129 | } |
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130 | } |
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131 | /* Set number of destinations */ |
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132 | dstcount = i; |
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133 | |
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134 | /* Create receiving socket */ |
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135 | if ((rcvfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) { |
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136 | perror("rcvfd socket"); |
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137 | return 1; |
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138 | } |
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139 | |
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140 | /* Allow UDP broadcasts on receiving socket */ |
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141 | optval = 1; |
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142 | if (setsockopt(rcvfd, SOL_SOCKET, SO_BROADCAST, &optval, sizeof(int)) < 0) { |
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143 | perror("setsockopt(rcvfd, SOL_SOCKET, SO_BROADCAST, ...)"); |
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144 | return 1; |
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145 | }; |
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146 | |
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147 | /* Set properties of source address */ |
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148 | srcaddr.sin_family = AF_INET; |
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149 | srcaddr.sin_port = htons(lstport); |
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150 | if ((inet_pton(AF_INET, argv[1], &srcaddr.sin_addr.s_addr)) != 1) { |
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151 | fprintf(stderr, "lst-addr is invalid\n"); |
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152 | return 1; |
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153 | } |
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154 | |
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155 | /* Bind the receiving socket */ |
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156 | if (bind(rcvfd, (struct sockaddr*)&srcaddr, sizeof(struct sockaddr_in)) < 0) { |
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157 | perror("bind"); |
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158 | return 1; |
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159 | } |
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160 | |
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161 | /* Create sending socket */ |
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162 | if ((sndfd = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0) { |
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163 | perror("sndfd socket"); |
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164 | return 1; |
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165 | } |
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166 | |
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167 | /* Allow UDP broadcasts on sending socket -- LCFIB --*/ |
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168 | if (setsockopt (sndfd, SOL_SOCKET, SO_BROADCAST, &optval, sizeof(int)) < 0) { |
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169 | perror("setsockopt(sndfd, SOL_SOCKET, SO_BROADCAST, ...)"); |
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170 | return 1; |
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171 | } |
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172 | |
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173 | /* Set destination port in outgoing packet */ |
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174 | *(u_short *)(packet + 22) = (u_short)htons(dstport); |
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175 | |
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176 | /* Allow setting outgoing header manually */ |
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177 | optval = 1; |
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178 | if (setsockopt(sndfd, IPPROTO_IP, IP_HDRINCL, &optval, sizeof(int)) < 0) { |
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179 | perror("setsockopt(sndfd, IPPROTO_IP, IP_HDRINCL, ...)"); |
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180 | return 1; |
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181 | } |
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182 | |
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183 | /* Main loop */ |
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184 | for ( ; ; ) { |
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185 | /* Wait for a packet */ |
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186 | if (debug) printf("Waiting packet\n"); |
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187 | rcvlen = recvmsg(rcvfd, &rcvmsg, 0); |
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188 | |
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189 | if (rcvlen < 1) { |
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190 | /* Packet must not be broken */ |
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191 | continue; |
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192 | } |
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193 | |
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194 | // Debugging: |
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195 | if (debug) printf("Recv: %s:%d\n",inet_ntoa(srcaddr.sin_addr),srcaddr.sin_port); |
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196 | |
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197 | /* Grow packet */ |
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198 | packet[28 + rcvlen] = 0; |
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199 | |
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200 | /* Copy source packet source address/port into outgoing packet */ |
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201 | bcopy(&(srcaddr.sin_addr.s_addr), (packet + 12), 4); |
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202 | *(u_short *)(packet + 20) = (u_short)srcaddr.sin_port; |
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203 | |
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204 | /* Set length of outgoing packet */ |
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205 | *(u_short *)(packet + 24) = htons(8 + rcvlen); |
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206 | *(u_short *)(packet + 2) = htons(28 + rcvlen); |
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207 | |
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208 | for (i = 0; i < dstcount; i++) { |
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209 | /* Set destination of outgoing packet */ |
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210 | bcopy(&(dsts[i].dstaddr.sin_addr.s_addr), (packet + 16), 4); |
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211 | |
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212 | /* Send outgoing packet */ |
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213 | if (sendto(sndfd, &packet, 28 + rcvlen, 0, |
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214 | (struct sockaddr *)&dsts[i].dstaddr, |
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215 | sizeof(struct sockaddr)) |
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216 | < 0) { |
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217 | perror("sendto"); |
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218 | } |
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219 | |
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220 | // Debugging: |
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221 | if (debug) printf("Sent: %s:%d\n", inet_ntoa(dsts[i].dstaddr.sin_addr), |
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222 | ntohs(*(u_short *)(packet+22))); |
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223 | } |
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224 | } |
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225 | |
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226 | return 0; |
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227 | } |
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