1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * Packet ops
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4 | *
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5 | * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
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6 | *
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7 | * Licensed under GPLv2, see file LICENSE in this source tree.
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8 | */
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9 | #include <netinet/in.h>
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10 | #if (defined(__GLIBC__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 1) || defined _NEWLIB_VERSION
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11 | # include <netpacket/packet.h>
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12 | # include <net/ethernet.h>
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13 | #else
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14 | # include <asm/types.h>
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15 | # include <linux/if_packet.h>
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16 | # include <linux/if_ether.h>
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17 | #endif
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18 |
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19 | #include "common.h"
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20 | #include "dhcpd.h"
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21 |
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22 | void FAST_FUNC udhcp_init_header(struct dhcp_packet *packet, char type)
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23 | {
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24 | memset(packet, 0, sizeof(*packet));
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25 | packet->op = BOOTREQUEST; /* if client to a server */
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26 | switch (type) {
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27 | case DHCPOFFER:
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28 | case DHCPACK:
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29 | case DHCPNAK:
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30 | packet->op = BOOTREPLY; /* if server to client */
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31 | }
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32 | packet->htype = 1; /* ethernet */
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33 | packet->hlen = 6;
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34 | packet->cookie = htonl(DHCP_MAGIC);
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35 | if (DHCP_END != 0)
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36 | packet->options[0] = DHCP_END;
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37 | udhcp_add_simple_option(packet, DHCP_MESSAGE_TYPE, type);
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38 | }
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39 |
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40 | #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2
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41 | void FAST_FUNC udhcp_dump_packet(struct dhcp_packet *packet)
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42 | {
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43 | char buf[sizeof(packet->chaddr)*2 + 1];
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44 |
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45 | if (dhcp_verbose < 2)
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46 | return;
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47 |
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48 | bb_info_msg(
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49 | //" op %x"
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50 | //" htype %x"
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51 | " hlen %x"
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52 | //" hops %x"
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53 | " xid %x"
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54 | //" secs %x"
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55 | //" flags %x"
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56 | " ciaddr %x"
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57 | " yiaddr %x"
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58 | " siaddr %x"
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59 | " giaddr %x"
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60 | //" chaddr %s"
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61 | //" sname %s"
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62 | //" file %s"
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63 | //" cookie %x"
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64 | //" options %s"
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65 | //, packet->op
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66 | //, packet->htype
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67 | , packet->hlen
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68 | //, packet->hops
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69 | , packet->xid
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70 | //, packet->secs
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71 | //, packet->flags
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72 | , packet->ciaddr
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73 | , packet->yiaddr
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74 | , packet->siaddr_nip
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75 | , packet->gateway_nip
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76 | //, packet->chaddr[16]
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77 | //, packet->sname[64]
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78 | //, packet->file[128]
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79 | //, packet->cookie
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80 | //, packet->options[]
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81 | );
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82 | *bin2hex(buf, (void *) packet->chaddr, sizeof(packet->chaddr)) = '\0';
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83 | bb_info_msg(" chaddr %s", buf);
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84 | }
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85 | #endif
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86 |
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87 | /* Read a packet from socket fd, return -1 on read error, -2 on packet error */
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88 | int FAST_FUNC udhcp_recv_kernel_packet(struct dhcp_packet *packet, int fd)
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89 | {
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90 | int bytes;
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91 | unsigned char *vendor;
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92 |
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93 | memset(packet, 0, sizeof(*packet));
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94 | bytes = safe_read(fd, packet, sizeof(*packet));
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95 | if (bytes < 0) {
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96 | log1("Packet read error, ignoring");
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97 | return bytes; /* returns -1 */
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98 | }
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99 |
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100 | if (packet->cookie != htonl(DHCP_MAGIC)) {
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101 | bb_info_msg("Packet with bad magic, ignoring");
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102 | return -2;
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103 | }
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104 | log1("Received a packet");
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105 | udhcp_dump_packet(packet);
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106 |
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107 | if (packet->op == BOOTREQUEST) {
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108 | vendor = udhcp_get_option(packet, DHCP_VENDOR);
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109 | if (vendor) {
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110 | #if 0
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111 | static const char broken_vendors[][8] = {
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112 | "MSFT 98",
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113 | ""
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114 | };
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115 | int i;
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116 | for (i = 0; broken_vendors[i][0]; i++) {
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117 | if (vendor[OPT_LEN - OPT_DATA] == (uint8_t)strlen(broken_vendors[i])
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118 | && strncmp((char*)vendor, broken_vendors[i], vendor[OPT_LEN - OPT_DATA]) == 0
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119 | ) {
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120 | log1("Broken client (%s), forcing broadcast replies",
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121 | broken_vendors[i]);
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122 | packet->flags |= htons(BROADCAST_FLAG);
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123 | }
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124 | }
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125 | #else
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126 | if (vendor[OPT_LEN - OPT_DATA] == (uint8_t)(sizeof("MSFT 98")-1)
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127 | && memcmp(vendor, "MSFT 98", sizeof("MSFT 98")-1) == 0
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128 | ) {
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129 | log1("Broken client (%s), forcing broadcast replies", "MSFT 98");
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130 | packet->flags |= htons(BROADCAST_FLAG);
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131 | }
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132 | #endif
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133 | }
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134 | }
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135 |
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136 | return bytes;
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137 | }
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138 |
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139 | uint16_t FAST_FUNC udhcp_checksum(void *addr, int count)
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140 | {
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141 | /* Compute Internet Checksum for "count" bytes
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142 | * beginning at location "addr".
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143 | */
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144 | int32_t sum = 0;
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145 | uint16_t *source = (uint16_t *) addr;
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146 |
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147 | while (count > 1) {
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148 | /* This is the inner loop */
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149 | sum += *source++;
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150 | count -= 2;
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151 | }
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152 |
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153 | /* Add left-over byte, if any */
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154 | if (count > 0) {
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155 | /* Make sure that the left-over byte is added correctly both
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156 | * with little and big endian hosts */
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157 | uint16_t tmp = 0;
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158 | *(uint8_t*)&tmp = *(uint8_t*)source;
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159 | sum += tmp;
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160 | }
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161 | /* Fold 32-bit sum to 16 bits */
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162 | while (sum >> 16)
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163 | sum = (sum & 0xffff) + (sum >> 16);
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164 |
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165 | return ~sum;
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166 | }
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167 |
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168 | /* Construct a ip/udp header for a packet, send packet */
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169 | int FAST_FUNC udhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt,
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170 | uint32_t source_nip, int source_port,
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171 | uint32_t dest_nip, int dest_port, const uint8_t *dest_arp,
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172 | int ifindex)
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173 | {
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174 | struct sockaddr_ll dest_sll;
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175 | struct ip_udp_dhcp_packet packet;
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176 | unsigned padding;
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177 | int fd;
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178 | int result = -1;
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179 | const char *msg;
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180 |
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181 | fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
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182 | if (fd < 0) {
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183 | msg = "socket(%s)";
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184 | goto ret_msg;
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185 | }
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186 |
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187 | memset(&dest_sll, 0, sizeof(dest_sll));
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188 | memset(&packet, 0, offsetof(struct ip_udp_dhcp_packet, data));
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189 | packet.data = *dhcp_pkt; /* struct copy */
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190 |
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191 | dest_sll.sll_family = AF_PACKET;
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192 | dest_sll.sll_protocol = htons(ETH_P_IP);
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193 | dest_sll.sll_ifindex = ifindex;
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194 | dest_sll.sll_halen = 6;
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195 | memcpy(dest_sll.sll_addr, dest_arp, 6);
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196 |
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197 | if (bind(fd, (struct sockaddr *)&dest_sll, sizeof(dest_sll)) < 0) {
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198 | msg = "bind(%s)";
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199 | goto ret_close;
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200 | }
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201 |
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202 | /* We were sending full-sized DHCP packets (zero padded),
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203 | * but some badly configured servers were seen dropping them.
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204 | * Apparently they drop all DHCP packets >576 *ethernet* octets big,
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205 | * whereas they may only drop packets >576 *IP* octets big
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206 | * (which for typical Ethernet II means 590 octets: 6+6+2 + 576).
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207 | *
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208 | * In order to work with those buggy servers,
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209 | * we truncate packets after end option byte.
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210 | */
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211 | padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(packet.data.options);
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212 |
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213 | packet.ip.protocol = IPPROTO_UDP;
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214 | packet.ip.saddr = source_nip;
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215 | packet.ip.daddr = dest_nip;
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216 | packet.udp.source = htons(source_port);
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217 | packet.udp.dest = htons(dest_port);
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218 | /* size, excluding IP header: */
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219 | packet.udp.len = htons(UDP_DHCP_SIZE - padding);
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220 | /* for UDP checksumming, ip.len is set to UDP packet len */
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221 | packet.ip.tot_len = packet.udp.len;
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222 | packet.udp.check = udhcp_checksum(&packet, IP_UDP_DHCP_SIZE - padding);
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223 | /* but for sending, it is set to IP packet len */
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224 | packet.ip.tot_len = htons(IP_UDP_DHCP_SIZE - padding);
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225 | packet.ip.ihl = sizeof(packet.ip) >> 2;
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226 | packet.ip.version = IPVERSION;
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227 | packet.ip.ttl = IPDEFTTL;
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228 | packet.ip.check = udhcp_checksum(&packet.ip, sizeof(packet.ip));
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229 |
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230 | udhcp_dump_packet(dhcp_pkt);
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231 | result = sendto(fd, &packet, IP_UDP_DHCP_SIZE - padding, /*flags:*/ 0,
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232 | (struct sockaddr *) &dest_sll, sizeof(dest_sll));
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233 | msg = "sendto";
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234 | ret_close:
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235 | close(fd);
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236 | if (result < 0) {
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237 | ret_msg:
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238 | bb_perror_msg(msg, "PACKET");
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239 | }
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240 | return result;
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241 | }
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242 |
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243 | /* Let the kernel do all the work for packet generation */
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244 | int FAST_FUNC udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
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245 | uint32_t source_nip, int source_port,
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246 | uint32_t dest_nip, int dest_port)
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247 | {
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248 | struct sockaddr_in client;
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249 | unsigned padding;
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250 | int fd;
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251 | int result = -1;
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252 | const char *msg;
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253 |
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254 | fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
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255 | if (fd < 0) {
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256 | msg = "socket(%s)";
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257 | goto ret_msg;
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258 | }
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259 | setsockopt_reuseaddr(fd);
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260 |
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261 | memset(&client, 0, sizeof(client));
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262 | client.sin_family = AF_INET;
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263 | client.sin_port = htons(source_port);
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264 | client.sin_addr.s_addr = source_nip;
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265 | if (bind(fd, (struct sockaddr *)&client, sizeof(client)) == -1) {
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266 | msg = "bind(%s)";
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267 | goto ret_close;
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268 | }
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269 |
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270 | memset(&client, 0, sizeof(client));
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271 | client.sin_family = AF_INET;
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272 | client.sin_port = htons(dest_port);
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273 | client.sin_addr.s_addr = dest_nip;
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274 | if (connect(fd, (struct sockaddr *)&client, sizeof(client)) == -1) {
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275 | msg = "connect";
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276 | goto ret_close;
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277 | }
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278 |
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279 | udhcp_dump_packet(dhcp_pkt);
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280 |
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281 | padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(dhcp_pkt->options);
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282 | result = safe_write(fd, dhcp_pkt, DHCP_SIZE - padding);
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283 | msg = "write";
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284 | ret_close:
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285 | close(fd);
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286 | if (result < 0) {
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287 | ret_msg:
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288 | bb_perror_msg(msg, "UDP");
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289 | }
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290 | return result;
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291 | }
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