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 "dhcpc.h"
  16 #include "dhcpd.h"
  17 #include "options.h"
  18
  19
  20 /* globals */
  21 struct dyn_lease *g_leases;
  22 /* struct server_config_t server_config is in bb_common_bufsiz1 */
  23
  24
  25 int udhcpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  26 int udhcpd_main(int argc UNUSED_PARAM, char **argv)
  27 {
  28         fd_set rfds;
  29         int server_socket = -1, retval, max_sock;
  30         struct dhcp_packet packet;
  31         uint8_t *state;
  32         uint32_t static_lease_ip;
  33         unsigned timeout_end;
  34         unsigned num_ips;
  35         unsigned opt;
  36         struct option_set *option;
  37         struct dyn_lease *lease, fake_lease;
  38         IF_FEATURE_UDHCP_PORT(char *str_P;)
  39
  40 #if ENABLE_FEATURE_UDHCP_PORT
  41         SERVER_PORT = 67;
  42         CLIENT_PORT = 68;
  43 #endif
  44
  45 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
  46         opt_complementary = "vv";
  47 #endif
  48         opt = getopt32(argv, "fSv"
  49                 IF_FEATURE_UDHCP_PORT("P:", &str_P)
  50 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
  51                 , &dhcp_verbose
  52 #endif
  53                 );
  54         argv += optind;
  55         if (!(opt & 1)) { /* no -f */
  56                 bb_daemonize_or_rexec(0, argv);
  57                 logmode = LOGMODE_NONE;
  58         }
  59         if (opt & 2) { /* -S */
  60                 openlog(applet_name, LOG_PID, LOG_DAEMON);
  61                 logmode |= LOGMODE_SYSLOG;
  62         }
  63 #if ENABLE_FEATURE_UDHCP_PORT
  64         if (opt & 4) { /* -P */
  65                 SERVER_PORT = xatou16(str_P);
  66                 CLIENT_PORT = SERVER_PORT + 1;
  67         }
  68 #endif
  69         /* Would rather not do read_config before daemonization -
  70          * otherwise NOMMU machines will parse config twice */
  71         read_config(argv[0] ? argv[0] : DHCPD_CONF_FILE);
  72
  73         /* Make sure fd 0,1,2 are open */
  74         bb_sanitize_stdio();
  75         /* Equivalent of doing a fflush after every \n */
  76         setlinebuf(stdout);
  77
  78         /* Create pidfile */
  79         write_pidfile(server_config.pidfile);
  80         /* if (!..) bb_perror_msg("can't create pidfile %s", pidfile); */
  81
  82         bb_info_msg("%s (v"BB_VER") started", applet_name);
  83
  84         option = find_option(server_config.options, DHCP_LEASE_TIME);
  85         server_config.max_lease_sec = LEASE_TIME;
  86         if (option) {
  87                 move_from_unaligned32(server_config.max_lease_sec, option->data + OPT_DATA);
  88                 server_config.max_lease_sec = ntohl(server_config.max_lease_sec);
  89         }
  90
  91         /* Sanity check */
  92         num_ips = server_config.end_ip - server_config.start_ip + 1;
  93         if (server_config.max_leases > num_ips) {
  94                 bb_error_msg("max_leases=%u is too big, setting to %u",
  95                         (unsigned)server_config.max_leases, num_ips);
  96                 server_config.max_leases = num_ips;
  97         }
  98
  99         g_leases = xzalloc(server_config.max_leases * sizeof(g_leases[0]));
 100         read_leases(server_config.lease_file);
 101
 102         if (udhcp_read_interface(server_config.interface,
 103                         &server_config.ifindex,
 104                         &server_config.server_nip,
 105                         server_config.server_mac)
 106         ) {
 107                 retval = 1;
 108                 goto ret;
 109         }
 110
 111         /* Setup the signal pipe */
 112         udhcp_sp_setup();
 113
 114         timeout_end = monotonic_sec() + server_config.auto_time;
 115         while (1) { /* loop until universe collapses */
 116                 int bytes;
 117                 struct timeval tv;
 118
 119                 if (server_socket < 0) {
 120                         server_socket = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT,
 121                                         server_config.interface);
 122                 }
 123
 124                 max_sock = udhcp_sp_fd_set(&rfds, server_socket);
 125                 if (server_config.auto_time) {
 126                         tv.tv_sec = timeout_end - monotonic_sec();
 127                         tv.tv_usec = 0;
 128                 }
 129                 retval = 0;
 130                 if (!server_config.auto_time || tv.tv_sec > 0) {
 131                         retval = select(max_sock + 1, &rfds, NULL, NULL,
 132                                         server_config.auto_time ? &tv : NULL);
 133                 }
 134                 if (retval == 0) {
 135                         write_leases();
 136                         timeout_end = monotonic_sec() + server_config.auto_time;
 137                         continue;
 138                 }
 139                 if (retval < 0 && errno != EINTR) {
 140                         log1("Error on select");
 141                         continue;
 142                 }
 143
 144                 switch (udhcp_sp_read(&rfds)) {
 145                 case SIGUSR1:
 146                         bb_info_msg("Received a SIGUSR1");
 147                         write_leases();
 148                         /* why not just reset the timeout, eh */
 149                         timeout_end = monotonic_sec() + server_config.auto_time;
 150                         continue;
 151                 case SIGTERM:
 152                         bb_info_msg("Received a SIGTERM");
 153                         goto ret0;
 154                 case 0: /* no signal: read a packet */
 155                         break;
 156                 default: /* signal or error (probably EINTR): back to select */
 157                         continue;
 158                 }
 159
 160                 bytes = udhcp_recv_kernel_packet(&packet, server_socket);
 161                 if (bytes < 0) {
 162                         /* bytes can also be -2 ("bad packet data") */
 163                         if (bytes == -1 && errno != EINTR) {
 164                                 log1("Read error: %s, reopening socket", strerror(errno));
 165                                 close(server_socket);
 166                                 server_socket = -1;
 167                         }
 168                         continue;
 169                 }
 170
 171                 if (packet.hlen != 6) {
 172                         bb_error_msg("MAC length != 6, ignoring packet");
 173                         continue;
 174                 }
 175
 176                 state = get_option(&packet, DHCP_MESSAGE_TYPE);
 177                 if (state == NULL) {
 178                         bb_error_msg("no message type option, ignoring packet");
 179                         continue;
 180                 }
 181
 182                 /* Look for a static lease */
 183                 static_lease_ip = get_static_nip_by_mac(server_config.static_leases, &packet.chaddr);
 184                 if (static_lease_ip) {
 185                         bb_info_msg("Found static lease: %x", static_lease_ip);
 186
 187                         memcpy(&fake_lease.lease_mac, &packet.chaddr, 6);
 188                         fake_lease.lease_nip = static_lease_ip;
 189                         fake_lease.expires = 0;
 190
 191                         lease = &fake_lease;
 192                 } else {
 193                         lease = find_lease_by_mac(packet.chaddr);
 194                 }
 195
 196                 switch (state[0]) {
 197                 case DHCPDISCOVER:
 198                         log1("Received DISCOVER");
 199
 200                         if (send_offer(&packet) < 0) {
 201                                 bb_error_msg("send OFFER failed");
 202                         }
 203                         break;
 204                 case DHCPREQUEST: {
 205                         uint8_t *server_id_opt, *requested_opt;
 206                         uint32_t server_id_net = server_id_net; /* for compiler */
 207                         uint32_t requested_nip = requested_nip; /* for compiler */
 208
 209                         log1("Received REQUEST");
 210
 211                         requested_opt = get_option(&packet, DHCP_REQUESTED_IP);
 212                         server_id_opt = get_option(&packet, DHCP_SERVER_ID);
 213                         if (requested_opt)
 214                                 move_from_unaligned32(requested_nip, requested_opt);
 215                         if (server_id_opt)
 216                                 move_from_unaligned32(server_id_net, server_id_opt);
 217
 218                         if (lease) {
 219                                 if (server_id_opt) {
 220                                         /* SELECTING State */
 221                                         if (server_id_net == server_config.server_nip
 222                                          && requested_opt
 223                                          && requested_nip == lease->lease_nip
 224                                         ) {
 225                                                 send_ACK(&packet, lease->lease_nip);
 226                                         }
 227                                 } else if (requested_opt) {
 228                                         /* INIT-REBOOT State */
 229                                         if (lease->lease_nip == requested_nip)
 230                                                 send_ACK(&packet, lease->lease_nip);
 231                                         else
 232                                                 send_NAK(&packet);
 233                                 } else if (lease->lease_nip == packet.ciaddr) {
 234                                         /* RENEWING or REBINDING State */
 235                                         send_ACK(&packet, lease->lease_nip);
 236                                 } else { /* don't know what to do!!!! */
 237                                         send_NAK(&packet);
 238                                 }
 239
 240                         /* what to do if we have no record of the client */
 241                         } else if (server_id_opt) {
 242                                 /* SELECTING State */
 243
 244                         } else if (requested_opt) {
 245                                 /* INIT-REBOOT State */
 246                                 lease = find_lease_by_nip(requested_nip);
 247                                 if (lease) {
 248                                         if (is_expired_lease(lease)) {
 249                                                 /* probably best if we drop this lease */
 250                                                 memset(lease->lease_mac, 0, sizeof(lease->lease_mac));
 251                                         } else {
 252                                                 /* make some contention for this address */
 253                                                 send_NAK(&packet);
 254                                         }
 255                                 } else {
 256                                         uint32_t r = ntohl(requested_nip);
 257                                         if (r < server_config.start_ip
 258                                          || r > server_config.end_ip
 259                                         ) {
 260                                                 send_NAK(&packet);
 261                                         }
 262                                         /* else remain silent */
 263                                 }
 264
 265                         } else {
 266                                 /* RENEWING or REBINDING State */
 267                         }
 268                         break;
 269                 }
 270                 case DHCPDECLINE:
 271                         log1("Received DECLINE");
 272                         if (lease) {
 273                                 memset(lease->lease_mac, 0, sizeof(lease->lease_mac));
 274                                 lease->expires = time(NULL) + server_config.decline_time;
 275                         }
 276                         break;
 277                 case DHCPRELEASE:
 278                         log1("Received RELEASE");
 279                         if (lease)
 280                                 lease->expires = time(NULL);
 281                         break;
 282                 case DHCPINFORM:
 283                         log1("Received INFORM");
 284                         send_inform(&packet);
 285                         break;
 286                 default:
 287                         bb_info_msg("Unsupported DHCP message (%02x) - ignoring", state[0]);
 288                 }
 289         }
 290  ret0:
 291         retval = 0;
 292  ret:
 293         /*if (server_config.pidfile) - server_config.pidfile is never NULL */
 294                 remove_pidfile(server_config.pidfile);
 295         return retval;
 296 }