1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * udhcp server
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4 | * Copyright (C) 1999 Matthew Ramsay <matthewr@moreton.com.au>
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5 | * Chris Trew <ctrew@moreton.com.au>
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6 | *
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7 | * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
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8 | *
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9 | * This program is free software; you can redistribute it and/or modify
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10 | * it under the terms of the GNU General Public License as published by
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11 | * the Free Software Foundation; either version 2 of the License, or
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12 | * (at your option) any later version.
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13 | *
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14 | * This program is distributed in the hope that it will be useful,
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15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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17 | * GNU General Public License for more details.
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18 | *
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19 | * You should have received a copy of the GNU General Public License
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20 | * along with this program; if not, write to the Free Software
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21 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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22 | */
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23 | #include <syslog.h>
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24 | #include "common.h"
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25 | #include "dhcpc.h"
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26 | #include "dhcpd.h"
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27 |
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28 |
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29 | /* Send a packet to a specific mac address and ip address by creating our own ip packet */
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30 | static void send_packet_to_client(struct dhcp_packet *dhcp_pkt, int force_broadcast)
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31 | {
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32 | const uint8_t *chaddr;
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33 | uint32_t ciaddr;
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34 |
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35 | // Was:
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36 | //if (force_broadcast) { /* broadcast */ }
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37 | //else if (dhcp_pkt->ciaddr) { /* unicast to dhcp_pkt->ciaddr */ }
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38 | //else if (dhcp_pkt->flags & htons(BROADCAST_FLAG)) { /* broadcast */ }
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39 | //else { /* unicast to dhcp_pkt->yiaddr */ }
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40 | // But this is wrong: yiaddr is _our_ idea what client's IP is
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41 | // (for example, from lease file). Client may not know that,
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42 | // and may not have UDP socket listening on that IP!
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43 | // We should never unicast to dhcp_pkt->yiaddr!
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44 | // dhcp_pkt->ciaddr, OTOH, comes from client's request packet,
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45 | // and can be used.
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46 |
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47 | if (force_broadcast
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48 | || (dhcp_pkt->flags & htons(BROADCAST_FLAG))
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49 | || dhcp_pkt->ciaddr == 0
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50 | ) {
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51 | log1("Broadcasting packet to client");
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52 | ciaddr = INADDR_BROADCAST;
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53 | chaddr = MAC_BCAST_ADDR;
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54 | } else {
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55 | log1("Unicasting packet to client ciaddr");
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56 | ciaddr = dhcp_pkt->ciaddr;
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57 | chaddr = dhcp_pkt->chaddr;
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58 | }
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59 |
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60 | udhcp_send_raw_packet(dhcp_pkt,
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61 | /*src*/ server_config.server_nip, SERVER_PORT,
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62 | /*dst*/ ciaddr, CLIENT_PORT, chaddr,
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63 | server_config.ifindex);
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64 | }
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65 |
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66 | /* Send a packet to gateway_nip using the kernel ip stack */
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67 | static void send_packet_to_relay(struct dhcp_packet *dhcp_pkt)
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68 | {
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69 | log1("Forwarding packet to relay");
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70 |
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71 | udhcp_send_kernel_packet(dhcp_pkt,
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72 | server_config.server_nip, SERVER_PORT,
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73 | dhcp_pkt->gateway_nip, SERVER_PORT);
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74 | }
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75 |
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76 | static void send_packet(struct dhcp_packet *dhcp_pkt, int force_broadcast)
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77 | {
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78 | if (dhcp_pkt->gateway_nip)
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79 | send_packet_to_relay(dhcp_pkt);
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80 | else
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81 | send_packet_to_client(dhcp_pkt, force_broadcast);
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82 | }
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83 |
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84 | static void init_packet(struct dhcp_packet *packet, struct dhcp_packet *oldpacket, char type)
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85 | {
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86 | /* Sets op, htype, hlen, cookie fields
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87 | * and adds DHCP_MESSAGE_TYPE option */
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88 | udhcp_init_header(packet, type);
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89 |
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90 | packet->xid = oldpacket->xid;
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91 | memcpy(packet->chaddr, oldpacket->chaddr, sizeof(oldpacket->chaddr));
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92 | packet->flags = oldpacket->flags;
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93 | packet->gateway_nip = oldpacket->gateway_nip;
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94 | packet->ciaddr = oldpacket->ciaddr;
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95 | udhcp_add_simple_option(packet, DHCP_SERVER_ID, server_config.server_nip);
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96 | }
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97 |
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98 | /* Fill options field, siaddr_nip, and sname and boot_file fields.
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99 | * TODO: teach this code to use overload option.
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100 | */
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101 | static void add_server_options(struct dhcp_packet *packet)
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102 | {
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103 | struct option_set *curr = server_config.options;
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104 |
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105 | while (curr) {
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106 | if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
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107 | udhcp_add_binary_option(packet, curr->data);
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108 | curr = curr->next;
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109 | }
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110 |
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111 | packet->siaddr_nip = server_config.siaddr_nip;
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112 |
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113 | if (server_config.sname)
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114 | strncpy((char*)packet->sname, server_config.sname, sizeof(packet->sname) - 1);
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115 | if (server_config.boot_file)
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116 | strncpy((char*)packet->file, server_config.boot_file, sizeof(packet->file) - 1);
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117 | }
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118 |
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119 | static uint32_t select_lease_time(struct dhcp_packet *packet)
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120 | {
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121 | uint32_t lease_time_sec = server_config.max_lease_sec;
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122 | uint8_t *lease_time_opt = udhcp_get_option(packet, DHCP_LEASE_TIME);
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123 | if (lease_time_opt) {
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124 | move_from_unaligned32(lease_time_sec, lease_time_opt);
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125 | lease_time_sec = ntohl(lease_time_sec);
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126 | if (lease_time_sec > server_config.max_lease_sec)
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127 | lease_time_sec = server_config.max_lease_sec;
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128 | if (lease_time_sec < server_config.min_lease_sec)
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129 | lease_time_sec = server_config.min_lease_sec;
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130 | }
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131 | return lease_time_sec;
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132 | }
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133 |
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134 | /* We got a DHCP DISCOVER. Send an OFFER. */
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135 | /* NOINLINE: limit stack usage in caller */
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136 | static NOINLINE void send_offer(struct dhcp_packet *oldpacket, uint32_t static_lease_nip, struct dyn_lease *lease)
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137 | {
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138 | struct dhcp_packet packet;
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139 | uint32_t lease_time_sec;
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140 | struct in_addr addr;
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141 |
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142 | init_packet(&packet, oldpacket, DHCPOFFER);
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143 |
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144 | /* If it is a static lease, use its IP */
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145 | packet.yiaddr = static_lease_nip;
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146 | /* Else: */
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147 | if (!static_lease_nip) {
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148 | /* We have no static lease for client's chaddr */
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149 | uint32_t req_nip;
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150 | uint8_t *req_ip_opt;
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151 | const char *p_host_name;
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152 |
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153 | if (lease) {
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154 | /* We have a dynamic lease for client's chaddr.
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155 | * Reuse its IP (even if lease is expired).
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156 | * Note that we ignore requested IP in this case.
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157 | */
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158 | packet.yiaddr = lease->lease_nip;
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159 | }
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160 | /* Or: if client has requested an IP */
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161 | else if ((req_ip_opt = udhcp_get_option(oldpacket, DHCP_REQUESTED_IP)) != NULL
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162 | /* (read IP) */
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163 | && (move_from_unaligned32(req_nip, req_ip_opt), 1)
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164 | /* and the IP is in the lease range */
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165 | && ntohl(req_nip) >= server_config.start_ip
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166 | && ntohl(req_nip) <= server_config.end_ip
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167 | /* and */
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168 | && ( !(lease = find_lease_by_nip(req_nip)) /* is not already taken */
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169 | || is_expired_lease(lease) /* or is taken, but expired */
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170 | )
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171 | ) {
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172 | packet.yiaddr = req_nip;
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173 | }
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174 | else {
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175 | /* Otherwise, find a free IP */
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176 | packet.yiaddr = find_free_or_expired_nip(oldpacket->chaddr);
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177 | }
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178 |
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179 | if (!packet.yiaddr) {
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180 | bb_error_msg("no free IP addresses. OFFER abandoned");
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181 | return;
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182 | }
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183 | /* Reserve the IP for a short time hoping to get DHCPREQUEST soon */
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184 | p_host_name = (const char*) udhcp_get_option(oldpacket, DHCP_HOST_NAME);
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185 | lease = add_lease(packet.chaddr, packet.yiaddr,
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186 | server_config.offer_time,
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187 | p_host_name,
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188 | p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
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189 | );
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190 | if (!lease) {
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191 | bb_error_msg("no free IP addresses. OFFER abandoned");
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192 | return;
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193 | }
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194 | }
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195 |
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196 | lease_time_sec = select_lease_time(oldpacket);
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197 | udhcp_add_simple_option(&packet, DHCP_LEASE_TIME, htonl(lease_time_sec));
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198 | add_server_options(&packet);
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199 |
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200 | addr.s_addr = packet.yiaddr;
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201 | bb_info_msg("Sending OFFER of %s", inet_ntoa(addr));
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202 | /* send_packet emits error message itself if it detects failure */
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203 | send_packet(&packet, /*force_bcast:*/ 0);
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204 | }
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205 |
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206 | /* NOINLINE: limit stack usage in caller */
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207 | static NOINLINE void send_NAK(struct dhcp_packet *oldpacket)
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208 | {
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209 | struct dhcp_packet packet;
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210 |
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211 | init_packet(&packet, oldpacket, DHCPNAK);
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212 |
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213 | log1("Sending NAK");
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214 | send_packet(&packet, /*force_bcast:*/ 1);
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215 | }
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216 |
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217 | /* NOINLINE: limit stack usage in caller */
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218 | static NOINLINE void send_ACK(struct dhcp_packet *oldpacket, uint32_t yiaddr)
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219 | {
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220 | struct dhcp_packet packet;
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221 | uint32_t lease_time_sec;
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222 | struct in_addr addr;
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223 | const char *p_host_name;
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224 |
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225 | init_packet(&packet, oldpacket, DHCPACK);
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226 | packet.yiaddr = yiaddr;
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227 |
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228 | lease_time_sec = select_lease_time(oldpacket);
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229 | udhcp_add_simple_option(&packet, DHCP_LEASE_TIME, htonl(lease_time_sec));
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230 |
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231 | add_server_options(&packet);
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232 |
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233 | addr.s_addr = yiaddr;
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234 | bb_info_msg("Sending ACK to %s", inet_ntoa(addr));
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235 | send_packet(&packet, /*force_bcast:*/ 0);
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236 |
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237 | p_host_name = (const char*) udhcp_get_option(oldpacket, DHCP_HOST_NAME);
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238 | add_lease(packet.chaddr, packet.yiaddr,
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239 | lease_time_sec,
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240 | p_host_name,
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241 | p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
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242 | );
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243 | if (ENABLE_FEATURE_UDHCPD_WRITE_LEASES_EARLY) {
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244 | /* rewrite the file with leases at every new acceptance */
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245 | write_leases();
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246 | }
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247 | }
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248 |
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249 | /* NOINLINE: limit stack usage in caller */
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250 | static NOINLINE void send_inform(struct dhcp_packet *oldpacket)
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251 | {
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252 | struct dhcp_packet packet;
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253 |
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254 | /* "If a client has obtained a network address through some other means
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255 | * (e.g., manual configuration), it may use a DHCPINFORM request message
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256 | * to obtain other local configuration parameters. Servers receiving a
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257 | * DHCPINFORM message construct a DHCPACK message with any local
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258 | * configuration parameters appropriate for the client without:
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259 | * allocating a new address, checking for an existing binding, filling
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260 | * in 'yiaddr' or including lease time parameters. The servers SHOULD
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261 | * unicast the DHCPACK reply to the address given in the 'ciaddr' field
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262 | * of the DHCPINFORM message.
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263 | * ...
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264 | * The server responds to a DHCPINFORM message by sending a DHCPACK
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265 | * message directly to the address given in the 'ciaddr' field
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266 | * of the DHCPINFORM message. The server MUST NOT send a lease
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267 | * expiration time to the client and SHOULD NOT fill in 'yiaddr'."
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268 | */
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269 | //TODO: do a few sanity checks: is ciaddr set?
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270 | //Better yet: is ciaddr == IP source addr?
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271 | init_packet(&packet, oldpacket, DHCPACK);
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272 | add_server_options(&packet);
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273 |
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274 | send_packet(&packet, /*force_bcast:*/ 0);
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275 | }
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276 |
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277 |
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278 | /* globals */
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279 | struct dyn_lease *g_leases;
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280 | /* struct server_config_t server_config is in bb_common_bufsiz1 */
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281 |
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282 |
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283 | int udhcpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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284 | int udhcpd_main(int argc UNUSED_PARAM, char **argv)
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285 | {
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286 | fd_set rfds;
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287 | int server_socket = -1, retval, max_sock;
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288 | struct dhcp_packet packet;
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289 | uint8_t *state;
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290 | uint32_t static_lease_nip;
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291 | unsigned timeout_end;
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292 | unsigned num_ips;
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293 | unsigned opt;
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294 | struct option_set *option;
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295 | struct dyn_lease *lease, fake_lease;
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296 | IF_FEATURE_UDHCP_PORT(char *str_P;)
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297 |
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298 | #if ENABLE_FEATURE_UDHCP_PORT
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299 | SERVER_PORT = 67;
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300 | CLIENT_PORT = 68;
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301 | #endif
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302 |
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303 | #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
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304 | opt_complementary = "vv";
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305 | #endif
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306 | opt = getopt32(argv, "fSv"
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307 | IF_FEATURE_UDHCP_PORT("P:", &str_P)
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308 | #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
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309 | , &dhcp_verbose
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310 | #endif
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311 | );
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312 | if (!(opt & 1)) { /* no -f */
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313 | bb_daemonize_or_rexec(0, argv);
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314 | logmode = LOGMODE_NONE;
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315 | }
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316 | /* update argv after the possible vfork+exec in daemonize */
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317 | argv += optind;
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318 | if (opt & 2) { /* -S */
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319 | openlog(applet_name, LOG_PID, LOG_DAEMON);
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320 | logmode |= LOGMODE_SYSLOG;
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321 | }
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322 | #if ENABLE_FEATURE_UDHCP_PORT
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323 | if (opt & 8) { /* -P */
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324 | SERVER_PORT = xatou16(str_P);
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325 | CLIENT_PORT = SERVER_PORT + 1;
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326 | }
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327 | #endif
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328 | /* Would rather not do read_config before daemonization -
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329 | * otherwise NOMMU machines will parse config twice */
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330 | read_config(argv[0] ? argv[0] : DHCPD_CONF_FILE);
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331 |
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332 | /* Make sure fd 0,1,2 are open */
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333 | bb_sanitize_stdio();
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334 | /* Equivalent of doing a fflush after every \n */
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335 | setlinebuf(stdout);
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336 |
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337 | /* Create pidfile */
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338 | write_pidfile(server_config.pidfile);
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339 | /* if (!..) bb_perror_msg("can't create pidfile %s", pidfile); */
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340 |
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341 | bb_info_msg("%s (v"BB_VER") started", applet_name);
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342 |
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343 | option = udhcp_find_option(server_config.options, DHCP_LEASE_TIME);
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344 | server_config.max_lease_sec = DEFAULT_LEASE_TIME;
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345 | if (option) {
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346 | move_from_unaligned32(server_config.max_lease_sec, option->data + OPT_DATA);
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347 | server_config.max_lease_sec = ntohl(server_config.max_lease_sec);
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348 | }
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349 |
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350 | /* Sanity check */
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351 | num_ips = server_config.end_ip - server_config.start_ip + 1;
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352 | if (server_config.max_leases > num_ips) {
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353 | bb_error_msg("max_leases=%u is too big, setting to %u",
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354 | (unsigned)server_config.max_leases, num_ips);
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355 | server_config.max_leases = num_ips;
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356 | }
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357 |
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358 | g_leases = xzalloc(server_config.max_leases * sizeof(g_leases[0]));
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359 | read_leases(server_config.lease_file);
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360 |
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361 | if (udhcp_read_interface(server_config.interface,
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362 | &server_config.ifindex,
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363 | &server_config.server_nip,
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364 | server_config.server_mac)
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365 | ) {
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366 | retval = 1;
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367 | goto ret;
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368 | }
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369 |
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370 | /* Setup the signal pipe */
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371 | udhcp_sp_setup();
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372 |
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373 | timeout_end = monotonic_sec() + server_config.auto_time;
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374 | while (1) { /* loop until universe collapses */
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375 | int bytes;
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376 | struct timeval tv;
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377 | uint8_t *server_id_opt;
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378 | uint8_t *requested_opt;
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379 | uint32_t requested_nip = requested_nip; /* for compiler */
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380 |
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381 | if (server_socket < 0) {
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382 | server_socket = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT,
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383 | server_config.interface);
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384 | }
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385 |
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386 | max_sock = udhcp_sp_fd_set(&rfds, server_socket);
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387 | if (server_config.auto_time) {
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388 | tv.tv_sec = timeout_end - monotonic_sec();
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389 | tv.tv_usec = 0;
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390 | }
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391 | retval = 0;
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392 | if (!server_config.auto_time || tv.tv_sec > 0) {
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393 | retval = select(max_sock + 1, &rfds, NULL, NULL,
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394 | server_config.auto_time ? &tv : NULL);
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395 | }
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396 | if (retval == 0) {
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397 | write_leases();
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398 | timeout_end = monotonic_sec() + server_config.auto_time;
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399 | continue;
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400 | }
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401 | if (retval < 0 && errno != EINTR) {
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402 | log1("Error on select");
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403 | continue;
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404 | }
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405 |
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406 | switch (udhcp_sp_read(&rfds)) {
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407 | case SIGUSR1:
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408 | bb_info_msg("Received SIGUSR1");
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409 | write_leases();
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410 | /* why not just reset the timeout, eh */
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411 | timeout_end = monotonic_sec() + server_config.auto_time;
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412 | continue;
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413 | case SIGTERM:
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414 | bb_info_msg("Received SIGTERM");
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415 | goto ret0;
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416 | case 0: /* no signal: read a packet */
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417 | break;
|
---|
418 | default: /* signal or error (probably EINTR): back to select */
|
---|
419 | continue;
|
---|
420 | }
|
---|
421 |
|
---|
422 | bytes = udhcp_recv_kernel_packet(&packet, server_socket);
|
---|
423 | if (bytes < 0) {
|
---|
424 | /* bytes can also be -2 ("bad packet data") */
|
---|
425 | if (bytes == -1 && errno != EINTR) {
|
---|
426 | log1("Read error: %s, reopening socket", strerror(errno));
|
---|
427 | close(server_socket);
|
---|
428 | server_socket = -1;
|
---|
429 | }
|
---|
430 | continue;
|
---|
431 | }
|
---|
432 | if (packet.hlen != 6) {
|
---|
433 | bb_error_msg("MAC length != 6, ignoring packet");
|
---|
434 | continue;
|
---|
435 | }
|
---|
436 | if (packet.op != BOOTREQUEST) {
|
---|
437 | bb_error_msg("not a REQUEST, ignoring packet");
|
---|
438 | continue;
|
---|
439 | }
|
---|
440 | state = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
|
---|
441 | if (state == NULL || state[0] < DHCP_MINTYPE || state[0] > DHCP_MAXTYPE) {
|
---|
442 | bb_error_msg("no or bad message type option, ignoring packet");
|
---|
443 | continue;
|
---|
444 | }
|
---|
445 |
|
---|
446 | /* Look for a static/dynamic lease */
|
---|
447 | static_lease_nip = get_static_nip_by_mac(server_config.static_leases, &packet.chaddr);
|
---|
448 | if (static_lease_nip) {
|
---|
449 | bb_info_msg("Found static lease: %x", static_lease_nip);
|
---|
450 | memcpy(&fake_lease.lease_mac, &packet.chaddr, 6);
|
---|
451 | fake_lease.lease_nip = static_lease_nip;
|
---|
452 | fake_lease.expires = 0;
|
---|
453 | lease = &fake_lease;
|
---|
454 | } else {
|
---|
455 | lease = find_lease_by_mac(packet.chaddr);
|
---|
456 | }
|
---|
457 |
|
---|
458 | /* Get REQUESTED_IP and SERVER_ID if present */
|
---|
459 | server_id_opt = udhcp_get_option(&packet, DHCP_SERVER_ID);
|
---|
460 | if (server_id_opt) {
|
---|
461 | uint32_t server_id_net;
|
---|
462 | move_from_unaligned32(server_id_net, server_id_opt);
|
---|
463 | if (server_id_net != server_config.server_nip) {
|
---|
464 | /* client talks to somebody else */
|
---|
465 | log1("server ID doesn't match, ignoring");
|
---|
466 | continue;
|
---|
467 | }
|
---|
468 | }
|
---|
469 | requested_opt = udhcp_get_option(&packet, DHCP_REQUESTED_IP);
|
---|
470 | if (requested_opt) {
|
---|
471 | move_from_unaligned32(requested_nip, requested_opt);
|
---|
472 | }
|
---|
473 |
|
---|
474 | switch (state[0]) {
|
---|
475 |
|
---|
476 | case DHCPDISCOVER:
|
---|
477 | log1("Received DISCOVER");
|
---|
478 |
|
---|
479 | send_offer(&packet, static_lease_nip, lease);
|
---|
480 | break;
|
---|
481 |
|
---|
482 | case DHCPREQUEST:
|
---|
483 | log1("Received REQUEST");
|
---|
484 | /* RFC 2131:
|
---|
485 |
|
---|
486 | o DHCPREQUEST generated during SELECTING state:
|
---|
487 |
|
---|
488 | Client inserts the address of the selected server in 'server
|
---|
489 | identifier', 'ciaddr' MUST be zero, 'requested IP address' MUST be
|
---|
490 | filled in with the yiaddr value from the chosen DHCPOFFER.
|
---|
491 |
|
---|
492 | Note that the client may choose to collect several DHCPOFFER
|
---|
493 | messages and select the "best" offer. The client indicates its
|
---|
494 | selection by identifying the offering server in the DHCPREQUEST
|
---|
495 | message. If the client receives no acceptable offers, the client
|
---|
496 | may choose to try another DHCPDISCOVER message. Therefore, the
|
---|
497 | servers may not receive a specific DHCPREQUEST from which they can
|
---|
498 | decide whether or not the client has accepted the offer.
|
---|
499 |
|
---|
500 | o DHCPREQUEST generated during INIT-REBOOT state:
|
---|
501 |
|
---|
502 | 'server identifier' MUST NOT be filled in, 'requested IP address'
|
---|
503 | option MUST be filled in with client's notion of its previously
|
---|
504 | assigned address. 'ciaddr' MUST be zero. The client is seeking to
|
---|
505 | verify a previously allocated, cached configuration. Server SHOULD
|
---|
506 | send a DHCPNAK message to the client if the 'requested IP address'
|
---|
507 | is incorrect, or is on the wrong network.
|
---|
508 |
|
---|
509 | Determining whether a client in the INIT-REBOOT state is on the
|
---|
510 | correct network is done by examining the contents of 'giaddr', the
|
---|
511 | 'requested IP address' option, and a database lookup. If the DHCP
|
---|
512 | server detects that the client is on the wrong net (i.e., the
|
---|
513 | result of applying the local subnet mask or remote subnet mask (if
|
---|
514 | 'giaddr' is not zero) to 'requested IP address' option value
|
---|
515 | doesn't match reality), then the server SHOULD send a DHCPNAK
|
---|
516 | message to the client.
|
---|
517 |
|
---|
518 | If the network is correct, then the DHCP server should check if
|
---|
519 | the client's notion of its IP address is correct. If not, then the
|
---|
520 | server SHOULD send a DHCPNAK message to the client. If the DHCP
|
---|
521 | server has no record of this client, then it MUST remain silent,
|
---|
522 | and MAY output a warning to the network administrator. This
|
---|
523 | behavior is necessary for peaceful coexistence of non-
|
---|
524 | communicating DHCP servers on the same wire.
|
---|
525 |
|
---|
526 | If 'giaddr' is 0x0 in the DHCPREQUEST message, the client is on
|
---|
527 | the same subnet as the server. The server MUST broadcast the
|
---|
528 | DHCPNAK message to the 0xffffffff broadcast address because the
|
---|
529 | client may not have a correct network address or subnet mask, and
|
---|
530 | the client may not be answering ARP requests.
|
---|
531 |
|
---|
532 | If 'giaddr' is set in the DHCPREQUEST message, the client is on a
|
---|
533 | different subnet. The server MUST set the broadcast bit in the
|
---|
534 | DHCPNAK, so that the relay agent will broadcast the DHCPNAK to the
|
---|
535 | client, because the client may not have a correct network address
|
---|
536 | or subnet mask, and the client may not be answering ARP requests.
|
---|
537 |
|
---|
538 | o DHCPREQUEST generated during RENEWING state:
|
---|
539 |
|
---|
540 | 'server identifier' MUST NOT be filled in, 'requested IP address'
|
---|
541 | option MUST NOT be filled in, 'ciaddr' MUST be filled in with
|
---|
542 | client's IP address. In this situation, the client is completely
|
---|
543 | configured, and is trying to extend its lease. This message will
|
---|
544 | be unicast, so no relay agents will be involved in its
|
---|
545 | transmission. Because 'giaddr' is therefore not filled in, the
|
---|
546 | DHCP server will trust the value in 'ciaddr', and use it when
|
---|
547 | replying to the client.
|
---|
548 |
|
---|
549 | A client MAY choose to renew or extend its lease prior to T1. The
|
---|
550 | server may choose not to extend the lease (as a policy decision by
|
---|
551 | the network administrator), but should return a DHCPACK message
|
---|
552 | regardless.
|
---|
553 |
|
---|
554 | o DHCPREQUEST generated during REBINDING state:
|
---|
555 |
|
---|
556 | 'server identifier' MUST NOT be filled in, 'requested IP address'
|
---|
557 | option MUST NOT be filled in, 'ciaddr' MUST be filled in with
|
---|
558 | client's IP address. In this situation, the client is completely
|
---|
559 | configured, and is trying to extend its lease. This message MUST
|
---|
560 | be broadcast to the 0xffffffff IP broadcast address. The DHCP
|
---|
561 | server SHOULD check 'ciaddr' for correctness before replying to
|
---|
562 | the DHCPREQUEST.
|
---|
563 |
|
---|
564 | The DHCPREQUEST from a REBINDING client is intended to accommodate
|
---|
565 | sites that have multiple DHCP servers and a mechanism for
|
---|
566 | maintaining consistency among leases managed by multiple servers.
|
---|
567 | A DHCP server MAY extend a client's lease only if it has local
|
---|
568 | administrative authority to do so.
|
---|
569 | */
|
---|
570 | if (!requested_opt) {
|
---|
571 | requested_nip = packet.ciaddr;
|
---|
572 | if (requested_nip == 0) {
|
---|
573 | log1("no requested IP and no ciaddr, ignoring");
|
---|
574 | break;
|
---|
575 | }
|
---|
576 | }
|
---|
577 | if (lease && requested_nip == lease->lease_nip) {
|
---|
578 | /* client requested or configured IP matches the lease.
|
---|
579 | * ACK it, and bump lease expiration time. */
|
---|
580 | send_ACK(&packet, lease->lease_nip);
|
---|
581 | break;
|
---|
582 | }
|
---|
583 | if (server_id_opt) {
|
---|
584 | /* client was talking specifically to us.
|
---|
585 | * "No, we don't have this IP for you". */
|
---|
586 | send_NAK(&packet);
|
---|
587 | }
|
---|
588 | break;
|
---|
589 |
|
---|
590 | case DHCPDECLINE:
|
---|
591 | /* RFC 2131:
|
---|
592 | * "If the server receives a DHCPDECLINE message,
|
---|
593 | * the client has discovered through some other means
|
---|
594 | * that the suggested network address is already
|
---|
595 | * in use. The server MUST mark the network address
|
---|
596 | * as not available and SHOULD notify the local
|
---|
597 | * sysadmin of a possible configuration problem."
|
---|
598 | *
|
---|
599 | * SERVER_ID must be present,
|
---|
600 | * REQUESTED_IP must be present,
|
---|
601 | * chaddr must be filled in,
|
---|
602 | * ciaddr must be 0 (we do not check this)
|
---|
603 | */
|
---|
604 | log1("Received DECLINE");
|
---|
605 | if (server_id_opt
|
---|
606 | && requested_opt
|
---|
607 | && lease /* chaddr matches this lease */
|
---|
608 | && requested_nip == lease->lease_nip
|
---|
609 | ) {
|
---|
610 | memset(lease->lease_mac, 0, sizeof(lease->lease_mac));
|
---|
611 | lease->expires = time(NULL) + server_config.decline_time;
|
---|
612 | }
|
---|
613 | break;
|
---|
614 |
|
---|
615 | case DHCPRELEASE:
|
---|
616 | /* "Upon receipt of a DHCPRELEASE message, the server
|
---|
617 | * marks the network address as not allocated."
|
---|
618 | *
|
---|
619 | * SERVER_ID must be present,
|
---|
620 | * REQUESTED_IP must not be present (we do not check this),
|
---|
621 | * chaddr must be filled in,
|
---|
622 | * ciaddr must be filled in
|
---|
623 | */
|
---|
624 | log1("Received RELEASE");
|
---|
625 | if (server_id_opt
|
---|
626 | && lease /* chaddr matches this lease */
|
---|
627 | && packet.ciaddr == lease->lease_nip
|
---|
628 | ) {
|
---|
629 | lease->expires = time(NULL);
|
---|
630 | }
|
---|
631 | break;
|
---|
632 |
|
---|
633 | case DHCPINFORM:
|
---|
634 | log1("Received INFORM");
|
---|
635 | send_inform(&packet);
|
---|
636 | break;
|
---|
637 | }
|
---|
638 | }
|
---|
639 | ret0:
|
---|
640 | retval = 0;
|
---|
641 | ret:
|
---|
642 | /*if (server_config.pidfile) - server_config.pidfile is never NULL */
|
---|
643 | remove_pidfile(server_config.pidfile);
|
---|
644 | return retval;
|
---|
645 | }
|
---|