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