networking/udhcp/dhcpd.c

   1 /* vi: set sw=4 ts=4: */
   2 /* dhcpd.c
   3  *
   4  * udhcp Server
   5  * Copyright (C) 1999 Matthew Ramsay <matthewr@moreton.com.au>
   6  *                      Chris Trew <ctrew@moreton.com.au>
   7  *
   8  * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
   9  *
  10  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
  11  */
  12
  13 #include <syslog.h>
  14 #include "common.h"
  15 #include "dhcpd.h"
  16 #include "options.h"
  17
  18
  19 /* globals */
  20 struct dhcpOfferedAddr *leases;
  21 struct server_config_t server_config;
  22
  23
  24 int udhcpd_main(int argc, char **argv);
  25 int udhcpd_main(int argc, char **argv)
  26 {
  27         fd_set rfds;
  28         struct timeval tv;
  29         int server_socket = -1, bytes, retval, max_sock;
  30         struct dhcpMessage packet;
  31         uint8_t *state, *server_id, *requested;
  32         uint32_t server_id_align, requested_align, static_lease_ip;
  33         unsigned timeout_end;
  34         unsigned num_ips;
  35         unsigned opt;
  36         struct option_set *option;
  37         struct dhcpOfferedAddr *lease, static_lease;
  38
  39         opt = getopt32(argc, argv, "fS");
  40         argv += optind;
  41
  42         if (!(opt & 1)) { /* no -f */
  43                 bb_daemonize_or_rexec(0, argv);
  44                 logmode &= ~LOGMODE_STDIO;
  45         }
  46
  47         if (opt & 2) { /* -S */
  48                 openlog(applet_name, LOG_PID, LOG_LOCAL0);
  49                 logmode |= LOGMODE_SYSLOG;
  50         }
  51
  52         /* Would rather not do read_config before daemonization -
  53          * otherwise NOMMU machines will parse config twice */
  54         read_config(argv[0] ? argv[0] : DHCPD_CONF_FILE);
  55
  56         /* Make sure fd 0,1,2 are open */
  57         bb_sanitize_stdio();
  58         /* Equivalent of doing a fflush after every \n */
  59         setlinebuf(stdout);
  60
  61         /* Create pidfile */
  62         write_pidfile(server_config.pidfile);
  63         /* if (!..) bb_perror_msg("cannot create pidfile %s", pidfile); */
  64
  65         bb_info_msg("%s (v%s) started", applet_name, BB_VER);
  66
  67         option = find_option(server_config.options, DHCP_LEASE_TIME);
  68         server_config.lease = LEASE_TIME;
  69         if (option) {
  70                 memcpy(&server_config.lease, option->data + 2, 4);
  71                 server_config.lease = ntohl(server_config.lease);
  72         }
  73
  74         /* Sanity check */
  75         num_ips = server_config.end_ip - server_config.start_ip + 1;
  76         if (server_config.max_leases > num_ips) {
  77                 bb_error_msg("max_leases=%u is too big, setting to %u",
  78                         (unsigned)server_config.max_leases, num_ips);
  79                 server_config.max_leases = num_ips;
  80         }
  81
  82         leases = xzalloc(server_config.max_leases * sizeof(*leases));
  83         read_leases(server_config.lease_file);
  84
  85         if (read_interface(server_config.interface, &server_config.ifindex,
  86                            &server_config.server, server_config.arp)) {
  87                 retval = 1;
  88                 goto ret;
  89         }
  90
  91         /* Setup the signal pipe */
  92         udhcp_sp_setup();
  93
  94         timeout_end = monotonic_sec() + server_config.auto_time;
  95         while (1) { /* loop until universe collapses */
  96
  97                 if (server_socket < 0) {
  98                         server_socket = listen_socket(/*INADDR_ANY,*/ SERVER_PORT,
  99                                         server_config.interface);
 100                 }
 101
 102                 max_sock = udhcp_sp_fd_set(&rfds, server_socket);
 103                 if (server_config.auto_time) {
 104                         tv.tv_sec = timeout_end - monotonic_sec();
 105                         tv.tv_usec = 0;
 106                 }
 107                 retval = 0;
 108                 if (!server_config.auto_time || tv.tv_sec > 0) {
 109                         retval = select(max_sock + 1, &rfds, NULL, NULL,
 110                                         server_config.auto_time ? &tv : NULL);
 111                 }
 112                 if (retval == 0) {
 113                         write_leases();
 114                         timeout_end = monotonic_sec() + server_config.auto_time;
 115                         continue;
 116                 }
 117                 if (retval < 0 && errno != EINTR) {
 118                         DEBUG("error on select");
 119                         continue;
 120                 }
 121
 122                 switch (udhcp_sp_read(&rfds)) {
 123                 case SIGUSR1:
 124                         bb_info_msg("Received a SIGUSR1");
 125                         write_leases();
 126                         /* why not just reset the timeout, eh */
 127                         timeout_end = monotonic_sec() + server_config.auto_time;
 128                         continue;
 129                 case SIGTERM:
 130                         bb_info_msg("Received a SIGTERM");
 131                         goto ret0;
 132                 case 0: break;          /* no signal */
 133                 default: continue;      /* signal or error (probably EINTR) */
 134                 }
 135
 136                 bytes = udhcp_get_packet(&packet, server_socket); /* this waits for a packet - idle */
 137                 if (bytes < 0) {
 138                         if (bytes == -1 && errno != EINTR) {
 139                                 DEBUG("error on read, %s, reopening socket", strerror(errno));
 140                                 close(server_socket);
 141                                 server_socket = -1;
 142                         }
 143                         continue;
 144                 }
 145
 146                 state = get_option(&packet, DHCP_MESSAGE_TYPE);
 147                 if (state == NULL) {
 148                         bb_error_msg("cannot get option from packet, ignoring");
 149                         continue;
 150                 }
 151
 152                 /* Look for a static lease */
 153                 static_lease_ip = getIpByMac(server_config.static_leases, &packet.chaddr);
 154
 155                 if (static_lease_ip) {
 156                         bb_info_msg("Found static lease: %x", static_lease_ip);
 157
 158                         memcpy(&static_lease.chaddr, &packet.chaddr, 16);
 159                         static_lease.yiaddr = static_lease_ip;
 160                         static_lease.expires = 0;
 161
 162                         lease = &static_lease;
 163                 } else {
 164                         lease = find_lease_by_chaddr(packet.chaddr);
 165                 }
 166
 167                 switch (state[0]) {
 168                 case DHCPDISCOVER:
 169                         DEBUG("Received DISCOVER");
 170
 171                         if (sendOffer(&packet) < 0) {
 172                                 bb_error_msg("send OFFER failed");
 173                         }
 174                         break;
 175                 case DHCPREQUEST:
 176                         DEBUG("received REQUEST");
 177
 178                         requested = get_option(&packet, DHCP_REQUESTED_IP);
 179                         server_id = get_option(&packet, DHCP_SERVER_ID);
 180
 181                         if (requested) memcpy(&requested_align, requested, 4);
 182                         if (server_id) memcpy(&server_id_align, server_id, 4);
 183
 184                         if (lease) {
 185                                 if (server_id) {
 186                                         /* SELECTING State */
 187                                         DEBUG("server_id = %08x", ntohl(server_id_align));
 188                                         if (server_id_align == server_config.server && requested
 189                                          && requested_align == lease->yiaddr
 190                                         ) {
 191                                                 sendACK(&packet, lease->yiaddr);
 192                                         }
 193                                 } else if (requested) {
 194                                         /* INIT-REBOOT State */
 195                                         if (lease->yiaddr == requested_align)
 196                                                 sendACK(&packet, lease->yiaddr);
 197                                         else
 198                                                 sendNAK(&packet);
 199                                 } else if (lease->yiaddr == packet.ciaddr) {
 200                                         /* RENEWING or REBINDING State */
 201                                         sendACK(&packet, lease->yiaddr);
 202                                 } else {
 203                                         /* don't know what to do!!!! */
 204                                         sendNAK(&packet);
 205                                 }
 206
 207                         /* what to do if we have no record of the client */
 208                         } else if (server_id) {
 209                                 /* SELECTING State */
 210
 211                         } else if (requested) {
 212                                 /* INIT-REBOOT State */
 213                                 lease = find_lease_by_yiaddr(requested_align);
 214                                 if (lease) {
 215                                         if (lease_expired(lease)) {
 216                                                 /* probably best if we drop this lease */
 217                                                 memset(lease->chaddr, 0, 16);
 218                                         /* make some contention for this address */
 219                                         } else
 220                                                 sendNAK(&packet);
 221                                 } else {
 222                                         uint32_t r = ntohl(requested_align);
 223                                         if (r < server_config.start_ip
 224                                          || r > server_config.end_ip
 225                                         ) {
 226                                                 sendNAK(&packet);
 227                                         }
 228                                         /* else remain silent */
 229                                 }
 230
 231                         } else {
 232                                 /* RENEWING or REBINDING State */
 233                         }
 234                         break;
 235                 case DHCPDECLINE:
 236                         DEBUG("Received DECLINE");
 237                         if (lease) {
 238                                 memset(lease->chaddr, 0, 16);
 239                                 lease->expires = time(0) + server_config.decline_time;
 240                         }
 241                         break;
 242                 case DHCPRELEASE:
 243                         DEBUG("Received RELEASE");
 244                         if (lease)
 245                                 lease->expires = time(0);
 246                         break;
 247                 case DHCPINFORM:
 248                         DEBUG("Received INFORM");
 249                         send_inform(&packet);
 250                         break;
 251                 default:
 252                         bb_info_msg("Unsupported DHCP message (%02x) - ignoring", state[0]);
 253                 }
 254         }
 255  ret0:
 256         retval = 0;
 257  ret:
 258         /*if (server_config.pidfile) - server_config.pidfile is never NULL */
 259                 remove_pidfile(server_config.pidfile);
 260         return retval;
 261 }