1 | /* vi: set sw=4 ts=4: */
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2 | /* Port to Busybox Copyright (C) 2006 Jesse Dutton <jessedutton@gmail.com>
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3 | *
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4 | * Licensed under GPL v2, see file LICENSE in this tarball for details.
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5 | *
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6 | * DHCP Relay for 'DHCPv4 Configuration of IPSec Tunnel Mode' support
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7 | * Copyright (C) 2002 Mario Strasser <mast@gmx.net>,
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8 | * Zuercher Hochschule Winterthur,
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9 | * Netbeat AG
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10 | * Upstream has GPL v2 or later
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11 | */
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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 | /* constants */
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18 | #define SELECT_TIMEOUT 5 /* select timeout in sec. */
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19 | #define MAX_LIFETIME 2*60 /* lifetime of an xid entry in sec. */
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20 | #define MAX_INTERFACES 9
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21 |
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22 |
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23 | /* This list holds information about clients. The xid_* functions manipulate this list. */
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24 | static struct xid_item {
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25 | uint32_t xid;
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26 | struct sockaddr_in ip;
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27 | int client;
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28 | time_t timestamp;
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29 | struct xid_item *next;
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30 | } dhcprelay_xid_list = {0, {0}, 0, 0, NULL};
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31 |
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32 |
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33 | static struct xid_item *xid_add(uint32_t xid, struct sockaddr_in *ip, int client)
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34 | {
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35 | struct xid_item *item;
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36 |
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37 | /* create new xid entry */
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38 | item = xmalloc(sizeof(struct xid_item));
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39 |
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40 | /* add xid entry */
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41 | item->ip = *ip;
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42 | item->xid = xid;
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43 | item->client = client;
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44 | item->timestamp = time(NULL);
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45 | item->next = dhcprelay_xid_list.next;
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46 | dhcprelay_xid_list.next = item;
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47 |
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48 | return item;
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49 | }
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50 |
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51 | static void xid_expire(void)
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52 | {
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53 | struct xid_item *item = dhcprelay_xid_list.next;
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54 | struct xid_item *last = &dhcprelay_xid_list;
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55 | time_t current_time = time(NULL);
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56 |
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57 | while (item != NULL) {
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58 | if ((current_time - item->timestamp) > MAX_LIFETIME) {
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59 | last->next = item->next;
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60 | free(item);
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61 | item = last->next;
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62 | } else {
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63 | last = item;
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64 | item = item->next;
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65 | }
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66 | }
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67 | }
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68 |
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69 | static struct xid_item *xid_find(uint32_t xid)
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70 | {
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71 | struct xid_item *item = dhcprelay_xid_list.next;
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72 | while (item != NULL) {
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73 | if (item->xid == xid) {
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74 | return item;
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75 | }
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76 | item = item->next;
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77 | }
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78 | return NULL;
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79 | }
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80 |
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81 | static void xid_del(uint32_t xid)
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82 | {
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83 | struct xid_item *item = dhcprelay_xid_list.next;
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84 | struct xid_item *last = &dhcprelay_xid_list;
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85 | while (item != NULL) {
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86 | if (item->xid == xid) {
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87 | last->next = item->next;
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88 | free(item);
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89 | item = last->next;
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90 | } else {
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91 | last = item;
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92 | item = item->next;
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93 | }
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94 | }
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95 | }
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96 |
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97 | /**
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98 | * get_dhcp_packet_type - gets the message type of a dhcp packet
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99 | * p - pointer to the dhcp packet
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100 | * returns the message type on success, -1 otherwise
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101 | */
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102 | static int get_dhcp_packet_type(struct dhcpMessage *p)
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103 | {
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104 | uint8_t *op;
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105 |
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106 | /* it must be either a BOOTREQUEST or a BOOTREPLY */
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107 | if (p->op != BOOTREQUEST && p->op != BOOTREPLY)
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108 | return -1;
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109 | /* get message type option */
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110 | op = get_option(p, DHCP_MESSAGE_TYPE);
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111 | if (op != NULL)
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112 | return op[0];
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113 | return -1;
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114 | }
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115 |
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116 | /**
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117 | * signal_handler - handles signals ;-)
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118 | * sig - sent signal
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119 | */
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120 | static smallint dhcprelay_stopflag;
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121 |
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122 | static void dhcprelay_signal_handler(int sig)
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123 | {
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124 | dhcprelay_stopflag = 1;
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125 | }
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126 |
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127 | /**
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128 | * get_client_devices - parses the devices list
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129 | * dev_list - comma separated list of devices
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130 | * returns array
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131 | */
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132 | static char **get_client_devices(char *dev_list, int *client_number)
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133 | {
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134 | char *s, *list, **client_dev;
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135 | int i, cn;
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136 |
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137 | /* copy list */
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138 | list = xstrdup(dev_list);
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139 | if (list == NULL) return NULL;
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140 |
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141 | /* get number of items */
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142 | for (s = dev_list, cn = 1; *s; s++)
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143 | if (*s == ',')
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144 | cn++;
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145 |
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146 | client_dev = xzalloc(cn * sizeof(*client_dev));
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147 |
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148 | /* parse list */
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149 | s = strtok(list, ",");
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150 | i = 0;
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151 | while (s != NULL) {
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152 | client_dev[i++] = xstrdup(s);
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153 | s = strtok(NULL, ",");
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154 | }
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155 |
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156 | /* free copy and exit */
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157 | free(list);
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158 | *client_number = cn;
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159 | return client_dev;
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160 | }
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161 |
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162 |
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163 | /* Creates listen sockets (in fds) and returns the number allocated. */
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164 | static int init_sockets(char **client, int num_clients,
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165 | char *server, int *fds, int *max_socket)
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166 | {
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167 | int i;
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168 |
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169 | /* talk to real server on bootps */
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170 | fds[0] = listen_socket(/*INADDR_ANY,*/ 67, server);
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171 | *max_socket = fds[0];
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172 |
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173 | /* array starts at 1 since server is 0 */
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174 | num_clients++;
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175 |
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176 | for (i = 1; i < num_clients; i++) {
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177 | /* listen for clients on bootps */
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178 | fds[i] = listen_socket(/*NADDR_ANY,*/ 67, client[i-1]);
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179 | if (fds[i] > *max_socket)
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180 | *max_socket = fds[i];
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181 | }
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182 |
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183 | return i;
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184 | }
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185 |
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186 |
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187 | /**
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188 | * pass_on() - forwards dhcp packets from client to server
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189 | * p - packet to send
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190 | * client - number of the client
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191 | */
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192 | static void pass_on(struct dhcpMessage *p, int packet_len, int client, int *fds,
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193 | struct sockaddr_in *client_addr, struct sockaddr_in *server_addr)
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194 | {
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195 | int res, type;
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196 | struct xid_item *item;
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197 |
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198 | /* check packet_type */
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199 | type = get_dhcp_packet_type(p);
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200 | if (type != DHCPDISCOVER && type != DHCPREQUEST
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201 | && type != DHCPDECLINE && type != DHCPRELEASE
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202 | && type != DHCPINFORM
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203 | ) {
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204 | return;
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205 | }
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206 |
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207 | /* create new xid entry */
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208 | item = xid_add(p->xid, client_addr, client);
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209 |
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210 | /* forward request to LAN (server) */
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211 | res = sendto(fds[0], p, packet_len, 0, (struct sockaddr*)server_addr,
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212 | sizeof(struct sockaddr_in));
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213 | if (res != packet_len) {
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214 | bb_perror_msg("pass_on");
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215 | return;
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216 | }
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217 | }
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218 |
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219 | /**
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220 | * pass_back() - forwards dhcp packets from server to client
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221 | * p - packet to send
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222 | */
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223 | static void pass_back(struct dhcpMessage *p, int packet_len, int *fds)
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224 | {
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225 | int res, type;
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226 | struct xid_item *item;
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227 |
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228 | /* check xid */
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229 | item = xid_find(p->xid);
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230 | if (!item) {
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231 | return;
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232 | }
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233 |
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234 | /* check packet type */
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235 | type = get_dhcp_packet_type(p);
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236 | if (type != DHCPOFFER && type != DHCPACK && type != DHCPNAK) {
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237 | return;
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238 | }
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239 |
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240 | if (item->ip.sin_addr.s_addr == htonl(INADDR_ANY))
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241 | item->ip.sin_addr.s_addr = htonl(INADDR_BROADCAST);
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242 | if (item->client > MAX_INTERFACES)
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243 | return;
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244 | res = sendto(fds[item->client], p, packet_len, 0, (struct sockaddr*)(&item->ip),
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245 | sizeof(item->ip));
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246 | if (res != packet_len) {
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247 | bb_perror_msg("pass_back");
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248 | return;
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249 | }
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250 |
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251 | /* remove xid entry */
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252 | xid_del(p->xid);
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253 | }
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254 |
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255 | static void dhcprelay_loop(int *fds, int num_sockets, int max_socket, char **clients,
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256 | struct sockaddr_in *server_addr, uint32_t gw_ip)
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257 | {
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258 | struct dhcpMessage dhcp_msg;
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259 | fd_set rfds;
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260 | size_t packlen;
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261 | socklen_t addr_size;
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262 | struct sockaddr_in client_addr;
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263 | struct timeval tv;
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264 | int i;
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265 |
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266 | while (!dhcprelay_stopflag) {
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267 | FD_ZERO(&rfds);
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268 | for (i = 0; i < num_sockets; i++)
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269 | FD_SET(fds[i], &rfds);
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270 | tv.tv_sec = SELECT_TIMEOUT;
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271 | tv.tv_usec = 0;
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272 | if (select(max_socket + 1, &rfds, NULL, NULL, &tv) > 0) {
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273 | /* server */
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274 | if (FD_ISSET(fds[0], &rfds)) {
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275 | packlen = udhcp_get_packet(&dhcp_msg, fds[0]);
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276 | if (packlen > 0) {
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277 | pass_back(&dhcp_msg, packlen, fds);
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278 | }
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279 | }
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280 | for (i = 1; i < num_sockets; i++) {
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281 | /* clients */
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282 | if (!FD_ISSET(fds[i], &rfds))
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283 | continue;
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284 | addr_size = sizeof(struct sockaddr_in);
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285 | packlen = recvfrom(fds[i], &dhcp_msg, sizeof(dhcp_msg), 0,
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286 | (struct sockaddr *)(&client_addr), &addr_size);
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287 | if (packlen <= 0)
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288 | continue;
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289 | if (read_interface(clients[i-1], NULL, &dhcp_msg.giaddr, NULL))
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290 | dhcp_msg.giaddr = gw_ip;
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291 | pass_on(&dhcp_msg, packlen, i, fds, &client_addr, server_addr);
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292 | }
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293 | }
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294 | xid_expire();
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295 | }
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296 | }
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297 |
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298 | int dhcprelay_main(int argc, char **argv);
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299 | int dhcprelay_main(int argc, char **argv)
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300 | {
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301 | int i, num_sockets, max_socket, fds[MAX_INTERFACES];
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302 | uint32_t gw_ip;
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303 | char **clients;
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304 | struct sockaddr_in server_addr;
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305 |
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306 | server_addr.sin_family = AF_INET;
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307 | server_addr.sin_port = htons(67);
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308 | if (argc == 4) {
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309 | if (!inet_aton(argv[3], &server_addr.sin_addr))
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310 | bb_perror_msg_and_die("didn't grok server");
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311 | } else if (argc == 3) {
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312 | server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
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313 | } else {
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314 | bb_show_usage();
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315 | }
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316 | clients = get_client_devices(argv[1], &num_sockets);
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317 | if (!clients) return 0;
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318 |
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319 | signal(SIGTERM, dhcprelay_signal_handler);
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320 | signal(SIGQUIT, dhcprelay_signal_handler);
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321 | signal(SIGINT, dhcprelay_signal_handler);
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322 |
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323 | num_sockets = init_sockets(clients, num_sockets, argv[2], fds, &max_socket);
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324 |
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325 | if (read_interface(argv[2], NULL, &gw_ip, NULL))
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326 | return 1;
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327 |
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328 | dhcprelay_loop(fds, num_sockets, max_socket, clients, &server_addr, gw_ip);
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329 |
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330 | if (ENABLE_FEATURE_CLEAN_UP) {
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331 | for (i = 0; i < num_sockets; i++) {
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332 | close(fds[i]);
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333 | free(clients[i]);
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334 | }
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335 | }
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336 |
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337 | return 0;
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338 | }
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