1 | /* serverpacket.c
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2 | *
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3 | * Construct and send DHCP server packets
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4 | *
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5 | * Russ Dill <Russ.Dill@asu.edu> July 2001
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6 | *
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7 | * This program is free software; you can redistribute it and/or modify
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8 | * it under the terms of the GNU General Public License as published by
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9 | * the Free Software Foundation; either version 2 of the License, or
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10 | * (at your option) any later version.
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11 | *
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12 | * This program is distributed in the hope that it will be useful,
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13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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15 | * GNU General Public License for more details.
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16 | *
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17 | * You should have received a copy of the GNU General Public License
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18 | * along with this program; if not, write to the Free Software
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19 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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20 | */
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21 |
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22 | #include <sys/socket.h>
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23 | #include <netinet/in.h>
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24 | #include <arpa/inet.h>
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25 | #include <string.h>
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26 | #include <time.h>
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27 |
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28 | #include "common.h"
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29 | #include "serverpacket.h"
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30 | #include "dhcpd.h"
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31 | #include "options.h"
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32 | #include "static_leases.h"
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33 |
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34 | /* send a packet to giaddr using the kernel ip stack */
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35 | static int send_packet_to_relay(struct dhcpMessage *payload)
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36 | {
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37 | DEBUG(LOG_INFO, "Forwarding packet to relay");
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38 |
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39 | return udhcp_kernel_packet(payload, server_config.server, SERVER_PORT,
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40 | payload->giaddr, SERVER_PORT);
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41 | }
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42 |
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43 |
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44 | /* send a packet to a specific arp address and ip address by creating our own ip packet */
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45 | static int send_packet_to_client(struct dhcpMessage *payload, int force_broadcast)
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46 | {
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47 | uint8_t *chaddr;
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48 | uint32_t ciaddr;
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49 |
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50 | if (force_broadcast) {
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51 | DEBUG(LOG_INFO, "broadcasting packet to client (NAK)");
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52 | ciaddr = INADDR_BROADCAST;
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53 | chaddr = MAC_BCAST_ADDR;
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54 | } else if (payload->ciaddr) {
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55 | DEBUG(LOG_INFO, "unicasting packet to client ciaddr");
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56 | ciaddr = payload->ciaddr;
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57 | chaddr = payload->chaddr;
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58 | } else if (ntohs(payload->flags) & BROADCAST_FLAG) {
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59 | DEBUG(LOG_INFO, "broadcasting packet to client (requested)");
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60 | ciaddr = INADDR_BROADCAST;
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61 | chaddr = MAC_BCAST_ADDR;
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62 | } else {
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63 | DEBUG(LOG_INFO, "unicasting packet to client yiaddr");
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64 | ciaddr = payload->yiaddr;
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65 | chaddr = payload->chaddr;
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66 | }
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67 | return udhcp_raw_packet(payload, server_config.server, SERVER_PORT,
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68 | ciaddr, CLIENT_PORT, chaddr, server_config.ifindex);
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69 | }
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70 |
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71 |
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72 | /* send a dhcp packet, if force broadcast is set, the packet will be broadcast to the client */
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73 | static int send_packet(struct dhcpMessage *payload, int force_broadcast)
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74 | {
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75 | int ret;
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76 |
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77 | if (payload->giaddr)
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78 | ret = send_packet_to_relay(payload);
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79 | else ret = send_packet_to_client(payload, force_broadcast);
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80 | return ret;
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81 | }
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82 |
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83 |
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84 | static void init_packet(struct dhcpMessage *packet, struct dhcpMessage *oldpacket, char type)
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85 | {
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86 | udhcp_init_header(packet, type);
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87 | packet->xid = oldpacket->xid;
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88 | memcpy(packet->chaddr, oldpacket->chaddr, 16);
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89 | packet->flags = oldpacket->flags;
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90 | packet->giaddr = oldpacket->giaddr;
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91 | packet->ciaddr = oldpacket->ciaddr;
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92 | add_simple_option(packet->options, DHCP_SERVER_ID, server_config.server);
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93 | }
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94 |
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95 |
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96 | /* add in the bootp options */
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97 | static void add_bootp_options(struct dhcpMessage *packet)
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98 | {
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99 | packet->siaddr = server_config.siaddr;
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100 | if (server_config.sname)
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101 | strncpy((char*)packet->sname, server_config.sname, sizeof(packet->sname) - 1);
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102 | if (server_config.boot_file)
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103 | strncpy((char*)packet->file, server_config.boot_file, sizeof(packet->file) - 1);
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104 | }
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105 |
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106 |
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107 | /* send a DHCP OFFER to a DHCP DISCOVER */
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108 | int sendOffer(struct dhcpMessage *oldpacket)
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109 | {
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110 | struct dhcpMessage packet;
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111 | struct dhcpOfferedAddr *lease = NULL;
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112 | uint32_t req_align, lease_time_align = server_config.lease;
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113 | uint8_t *req, *lease_time;
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114 | struct option_set *curr;
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115 | struct in_addr addr;
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116 |
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117 | uint32_t static_lease_ip;
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118 |
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119 | init_packet(&packet, oldpacket, DHCPOFFER);
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120 |
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121 | static_lease_ip = getIpByMac(server_config.static_leases, oldpacket->chaddr);
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122 |
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123 | /* ADDME: if static, short circuit */
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124 | if(!static_lease_ip)
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125 | {
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126 | /* the client is in our lease/offered table */
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127 | if ((lease = find_lease_by_chaddr(oldpacket->chaddr))) {
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128 | if (!lease_expired(lease))
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129 | lease_time_align = lease->expires - time(0);
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130 | packet.yiaddr = lease->yiaddr;
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131 |
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132 | /* Or the client has a requested ip */
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133 | } else if ((req = get_option(oldpacket, DHCP_REQUESTED_IP)) &&
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134 |
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135 | /* Don't look here (ugly hackish thing to do) */
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136 | memcpy(&req_align, req, 4) &&
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137 |
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138 | /* and the ip is in the lease range */
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139 | ntohl(req_align) >= ntohl(server_config.start) &&
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140 | ntohl(req_align) <= ntohl(server_config.end) &&
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141 |
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142 | !static_lease_ip && /* Check that its not a static lease */
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143 | /* and is not already taken/offered */
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144 | ((!(lease = find_lease_by_yiaddr(req_align)) ||
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145 |
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146 | /* or its taken, but expired */ /* ADDME: or maybe in here */
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147 | lease_expired(lease)))) {
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148 | packet.yiaddr = req_align; /* FIXME: oh my, is there a host using this IP? */
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149 |
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150 | /* otherwise, find a free IP */
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151 | } else {
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152 | /* Is it a static lease? (No, because find_address skips static lease) */
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153 | packet.yiaddr = find_address(0);
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154 |
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155 | /* try for an expired lease */
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156 | if (!packet.yiaddr) packet.yiaddr = find_address(1);
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157 | }
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158 |
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159 | if(!packet.yiaddr) {
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160 | LOG(LOG_WARNING, "no IP addresses to give -- OFFER abandoned");
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161 | return -1;
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162 | }
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163 |
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164 | if (!add_lease(packet.chaddr, packet.yiaddr, server_config.offer_time)) {
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165 | LOG(LOG_WARNING, "lease pool is full -- OFFER abandoned");
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166 | return -1;
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167 | }
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168 |
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169 | if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
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170 | memcpy(&lease_time_align, lease_time, 4);
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171 | lease_time_align = ntohl(lease_time_align);
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172 | if (lease_time_align > server_config.lease)
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173 | lease_time_align = server_config.lease;
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174 | }
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175 |
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176 | /* Make sure we aren't just using the lease time from the previous offer */
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177 | if (lease_time_align < server_config.min_lease)
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178 | lease_time_align = server_config.lease;
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179 | }
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180 | /* ADDME: end of short circuit */
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181 | else
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182 | {
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183 | /* It is a static lease... use it */
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184 | packet.yiaddr = static_lease_ip;
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185 | }
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186 |
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187 | add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
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188 |
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189 | curr = server_config.options;
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190 | while (curr) {
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191 | if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
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192 | add_option_string(packet.options, curr->data);
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193 | curr = curr->next;
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194 | }
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195 |
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196 | add_bootp_options(&packet);
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197 |
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198 | addr.s_addr = packet.yiaddr;
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199 | LOG(LOG_INFO, "sending OFFER of %s", inet_ntoa(addr));
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200 | return send_packet(&packet, 0);
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201 | }
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202 |
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203 |
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204 | int sendNAK(struct dhcpMessage *oldpacket)
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205 | {
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206 | struct dhcpMessage packet;
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207 |
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208 | init_packet(&packet, oldpacket, DHCPNAK);
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209 |
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210 | DEBUG(LOG_INFO, "sending NAK");
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211 | return send_packet(&packet, 1);
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212 | }
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213 |
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214 |
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215 | int sendACK(struct dhcpMessage *oldpacket, uint32_t yiaddr)
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216 | {
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217 | struct dhcpMessage packet;
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218 | struct option_set *curr;
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219 | uint8_t *lease_time;
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220 | uint32_t lease_time_align = server_config.lease;
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221 | struct in_addr addr;
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222 |
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223 | init_packet(&packet, oldpacket, DHCPACK);
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224 | packet.yiaddr = yiaddr;
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225 |
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226 | if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
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227 | memcpy(&lease_time_align, lease_time, 4);
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228 | lease_time_align = ntohl(lease_time_align);
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229 | if (lease_time_align > server_config.lease)
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230 | lease_time_align = server_config.lease;
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231 | else if (lease_time_align < server_config.min_lease)
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232 | lease_time_align = server_config.lease;
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233 | }
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234 |
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235 | add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
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236 |
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237 | curr = server_config.options;
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238 | while (curr) {
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239 | if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
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240 | add_option_string(packet.options, curr->data);
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241 | curr = curr->next;
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242 | }
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243 |
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244 | add_bootp_options(&packet);
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245 |
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246 | addr.s_addr = packet.yiaddr;
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247 | LOG(LOG_INFO, "sending ACK to %s", inet_ntoa(addr));
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248 |
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249 | if (send_packet(&packet, 0) < 0)
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250 | return -1;
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251 |
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252 | add_lease(packet.chaddr, packet.yiaddr, lease_time_align);
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253 |
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254 | return 0;
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255 | }
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256 |
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257 |
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258 | int send_inform(struct dhcpMessage *oldpacket)
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259 | {
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260 | struct dhcpMessage packet;
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261 | struct option_set *curr;
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262 |
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263 | init_packet(&packet, oldpacket, DHCPACK);
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264 |
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265 | curr = server_config.options;
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266 | while (curr) {
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267 | if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
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268 | add_option_string(packet.options, curr->data);
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269 | curr = curr->next;
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270 | }
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271 |
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272 | add_bootp_options(&packet);
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273 |
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274 | return send_packet(&packet, 0);
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275 | }
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