1 | /* vi: set sw=4 ts=4: */
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2 |
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3 | #include <netinet/in.h>
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4 | #if (defined(__GLIBC__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 1) || defined _NEWLIB_VERSION
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5 | #include <netpacket/packet.h>
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6 | #include <net/ethernet.h>
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7 | #else
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8 | #include <asm/types.h>
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9 | #include <linux/if_packet.h>
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10 | #include <linux/if_ether.h>
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11 | #endif
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12 |
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13 | #include "common.h"
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14 | #include "dhcpd.h"
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15 | #include "options.h"
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16 |
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17 |
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18 | void udhcp_init_header(struct dhcpMessage *packet, char type)
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19 | {
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20 | memset(packet, 0, sizeof(struct dhcpMessage));
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21 | switch (type) {
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22 | case DHCPDISCOVER:
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23 | case DHCPREQUEST:
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24 | case DHCPRELEASE:
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25 | case DHCPINFORM:
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26 | packet->op = BOOTREQUEST;
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27 | break;
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28 | case DHCPOFFER:
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29 | case DHCPACK:
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30 | case DHCPNAK:
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31 | packet->op = BOOTREPLY;
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32 | }
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33 | packet->htype = ETH_10MB;
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34 | packet->hlen = ETH_10MB_LEN;
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35 | packet->cookie = htonl(DHCP_MAGIC);
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36 | packet->options[0] = DHCP_END;
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37 | add_simple_option(packet->options, DHCP_MESSAGE_TYPE, type);
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38 | }
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39 |
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40 |
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41 | /* read a packet from socket fd, return -1 on read error, -2 on packet error */
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42 | int udhcp_get_packet(struct dhcpMessage *packet, int fd)
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43 | {
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44 | #if 0
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45 | static const char broken_vendors[][8] = {
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46 | "MSFT 98",
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47 | ""
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48 | };
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49 | #endif
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50 | int bytes;
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51 | unsigned char *vendor;
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52 |
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53 | memset(packet, 0, sizeof(*packet));
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54 | bytes = read(fd, packet, sizeof(*packet));
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55 | if (bytes < 0) {
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56 | DEBUG("cannot read on listening socket, ignoring");
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57 | return -1;
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58 | }
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59 |
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60 | if (ntohl(packet->cookie) != DHCP_MAGIC) {
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61 | bb_error_msg("received bogus message, ignoring");
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62 | return -2;
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63 | }
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64 | DEBUG("Received a packet");
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65 |
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66 | if (packet->op == BOOTREQUEST) {
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67 | vendor = get_option(packet, DHCP_VENDOR);
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68 | if (vendor) {
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69 | #if 0
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70 | int i;
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71 | for (i = 0; broken_vendors[i][0]; i++) {
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72 | if (vendor[OPT_LEN - 2] == (uint8_t)strlen(broken_vendors[i])
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73 | && !strncmp((char*)vendor, broken_vendors[i], vendor[OPT_LEN - 2])
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74 | ) {
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75 | DEBUG("broken client (%s), forcing broadcast",
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76 | broken_vendors[i]);
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77 | packet->flags |= htons(BROADCAST_FLAG);
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78 | }
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79 | }
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80 | #else
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81 | if (vendor[OPT_LEN - 2] == (uint8_t)(sizeof("MSFT 98")-1)
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82 | && memcmp(vendor, "MSFT 98", sizeof("MSFT 98")-1) == 0
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83 | ) {
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84 | DEBUG("broken client (%s), forcing broadcast", "MSFT 98");
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85 | packet->flags |= htons(BROADCAST_FLAG);
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86 | }
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87 | #endif
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88 | }
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89 | }
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90 |
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91 | return bytes;
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92 | }
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93 |
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94 |
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95 | uint16_t udhcp_checksum(void *addr, int count)
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96 | {
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97 | /* Compute Internet Checksum for "count" bytes
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98 | * beginning at location "addr".
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99 | */
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100 | int32_t sum = 0;
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101 | uint16_t *source = (uint16_t *) addr;
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102 |
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103 | while (count > 1) {
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104 | /* This is the inner loop */
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105 | sum += *source++;
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106 | count -= 2;
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107 | }
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108 |
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109 | /* Add left-over byte, if any */
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110 | if (count > 0) {
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111 | /* Make sure that the left-over byte is added correctly both
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112 | * with little and big endian hosts */
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113 | uint16_t tmp = 0;
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114 | *(uint8_t *) (&tmp) = * (uint8_t *) source;
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115 | sum += tmp;
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116 | }
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117 | /* Fold 32-bit sum to 16 bits */
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118 | while (sum >> 16)
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119 | sum = (sum & 0xffff) + (sum >> 16);
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120 |
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121 | return ~sum;
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122 | }
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123 |
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124 |
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125 | /* Construct a ip/udp header for a packet, and specify the source and dest hardware address */
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126 | void BUG_sizeof_struct_udp_dhcp_packet_must_be_576(void);
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127 | int udhcp_raw_packet(struct dhcpMessage *payload,
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128 | uint32_t source_ip, int source_port,
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129 | uint32_t dest_ip, int dest_port, const uint8_t *dest_arp, int ifindex)
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130 | {
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131 | int fd;
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132 | int result;
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133 | struct sockaddr_ll dest;
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134 | struct udp_dhcp_packet packet;
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135 |
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136 | fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
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137 | if (fd < 0) {
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138 | bb_perror_msg("socket");
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139 | return -1;
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140 | }
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141 |
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142 | memset(&dest, 0, sizeof(dest));
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143 | memset(&packet, 0, sizeof(packet));
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144 |
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145 | dest.sll_family = AF_PACKET;
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146 | dest.sll_protocol = htons(ETH_P_IP);
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147 | dest.sll_ifindex = ifindex;
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148 | dest.sll_halen = 6;
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149 | memcpy(dest.sll_addr, dest_arp, 6);
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150 | if (bind(fd, (struct sockaddr *)&dest, sizeof(struct sockaddr_ll)) < 0) {
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151 | bb_perror_msg("bind");
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152 | close(fd);
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153 | return -1;
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154 | }
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155 |
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156 | packet.ip.protocol = IPPROTO_UDP;
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157 | packet.ip.saddr = source_ip;
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158 | packet.ip.daddr = dest_ip;
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159 | packet.udp.source = htons(source_port);
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160 | packet.udp.dest = htons(dest_port);
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161 | packet.udp.len = htons(sizeof(packet.udp) + sizeof(struct dhcpMessage)); /* cheat on the psuedo-header */
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162 | packet.ip.tot_len = packet.udp.len;
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163 | memcpy(&(packet.data), payload, sizeof(struct dhcpMessage));
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164 | packet.udp.check = udhcp_checksum(&packet, sizeof(struct udp_dhcp_packet));
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165 |
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166 | packet.ip.tot_len = htons(sizeof(struct udp_dhcp_packet));
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167 | packet.ip.ihl = sizeof(packet.ip) >> 2;
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168 | packet.ip.version = IPVERSION;
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169 | packet.ip.ttl = IPDEFTTL;
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170 | packet.ip.check = udhcp_checksum(&(packet.ip), sizeof(packet.ip));
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171 |
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172 | if (sizeof(struct udp_dhcp_packet) != 576)
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173 | BUG_sizeof_struct_udp_dhcp_packet_must_be_576();
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174 |
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175 | result = sendto(fd, &packet, sizeof(struct udp_dhcp_packet), 0,
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176 | (struct sockaddr *) &dest, sizeof(dest));
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177 | if (result <= 0) {
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178 | bb_perror_msg("sendto");
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179 | }
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180 | close(fd);
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181 | return result;
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182 | }
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183 |
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184 |
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185 | /* Let the kernel do all the work for packet generation */
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186 | int udhcp_kernel_packet(struct dhcpMessage *payload,
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187 | uint32_t source_ip, int source_port,
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188 | uint32_t dest_ip, int dest_port)
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189 | {
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190 | int fd, result;
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191 | struct sockaddr_in client;
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192 |
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193 | fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
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194 | if (fd < 0)
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195 | return -1;
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196 |
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197 | setsockopt_reuseaddr(fd);
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198 |
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199 | memset(&client, 0, sizeof(client));
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200 | client.sin_family = AF_INET;
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201 | client.sin_port = htons(source_port);
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202 | client.sin_addr.s_addr = source_ip;
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203 |
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204 | if (bind(fd, (struct sockaddr *)&client, sizeof(client)) == -1) {
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205 | close(fd);
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206 | return -1;
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207 | }
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208 |
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209 | memset(&client, 0, sizeof(client));
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210 | client.sin_family = AF_INET;
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211 | client.sin_port = htons(dest_port);
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212 | client.sin_addr.s_addr = dest_ip;
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213 |
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214 | if (connect(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1) {
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215 | close(fd);
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216 | return -1;
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217 | }
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218 |
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219 | result = write(fd, payload, sizeof(struct dhcpMessage));
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220 | close(fd);
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221 | return result;
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222 | }
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