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 dhcpOfferedAddr *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         struct timeval tv;
  30         int server_socket = -1, bytes, retval, max_sock;
  31         struct dhcpMessage packet;
  32         uint8_t *state, *server_id, *requested;
  33         uint32_t server_id_aligned = server_id_aligned; /* for compiler */
  34         uint32_t requested_aligned = requested_aligned;
  35         uint32_t static_lease_ip;
  36         unsigned timeout_end;
  37         unsigned num_ips;
  38         unsigned opt;
  39         struct option_set *option;
  40         struct dhcpOfferedAddr *lease, static_lease;
  41         USE_FEATURE_UDHCP_PORT(char *str_P;)
  42
  43 #if ENABLE_FEATURE_UDHCP_PORT
  44         SERVER_PORT = 67;
  45         CLIENT_PORT = 68;
  46 #endif
  47
  48         opt = getopt32(argv, "fS" USE_FEATURE_UDHCP_PORT("P:", &str_P));
  49         argv += optind;
  50
  51         if (!(opt & 1)) { /* no -f */
  52                 bb_daemonize_or_rexec(0, argv);
  53                 logmode &= ~LOGMODE_STDIO;
  54         }
  55
  56         if (opt & 2) { /* -S */
  57                 openlog(applet_name, LOG_PID, LOG_LOCAL0);
  58                 logmode |= LOGMODE_SYSLOG;
  59         }
  60 #if ENABLE_FEATURE_UDHCP_PORT
  61         if (opt & 4) { /* -P */
  62                 SERVER_PORT = xatou16(str_P);
  63                 CLIENT_PORT = SERVER_PORT + 1;
  64         }
  65 #endif
  66         /* Would rather not do read_config before daemonization -
  67          * otherwise NOMMU machines will parse config twice */
  68         read_config(argv[0] ? argv[0] : DHCPD_CONF_FILE);
  69
  70         /* Make sure fd 0,1,2 are open */
  71         bb_sanitize_stdio();
  72         /* Equivalent of doing a fflush after every \n */
  73         setlinebuf(stdout);
  74
  75         /* Create pidfile */
  76         write_pidfile(server_config.pidfile);
  77         /* if (!..) bb_perror_msg("cannot create pidfile %s", pidfile); */
  78
  79         bb_info_msg("%s (v"BB_VER") started", applet_name);
  80
  81         option = find_option(server_config.options, DHCP_LEASE_TIME);
  82         server_config.lease = LEASE_TIME;
  83         if (option) {
  84                 move_from_unaligned32(server_config.lease, option->data + 2);
  85                 server_config.lease = ntohl(server_config.lease);
  86         }
  87
  88         /* Sanity check */
  89         num_ips = server_config.end_ip - server_config.start_ip + 1;
  90         if (server_config.max_leases > num_ips) {
  91                 bb_error_msg("max_leases=%u is too big, setting to %u",
  92                         (unsigned)server_config.max_leases, num_ips);
  93                 server_config.max_leases = num_ips;
  94         }
  95
  96         leases = xzalloc(server_config.max_leases * sizeof(*leases));
  97         read_leases(server_config.lease_file);
  98
  99         if (udhcp_read_interface(server_config.interface, &server_config.ifindex,
 100                            &server_config.server, server_config.arp)) {
 101                 retval = 1;
 102                 goto ret;
 103         }
 104
 105         /* Setup the signal pipe */
 106         udhcp_sp_setup();
 107
 108         timeout_end = monotonic_sec() + server_config.auto_time;
 109         while (1) { /* loop until universe collapses */
 110
 111                 if (server_socket < 0) {
 112                         server_socket = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT,
 113                                         server_config.interface);
 114                 }
 115
 116                 max_sock = udhcp_sp_fd_set(&rfds, server_socket);
 117                 if (server_config.auto_time) {
 118                         tv.tv_sec = timeout_end - monotonic_sec();
 119                         tv.tv_usec = 0;
 120                 }
 121                 retval = 0;
 122                 if (!server_config.auto_time || tv.tv_sec > 0) {
 123                         retval = select(max_sock + 1, &rfds, NULL, NULL,
 124                                         server_config.auto_time ? &tv : NULL);
 125                 }
 126                 if (retval == 0) {
 127                         write_leases();
 128                         timeout_end = monotonic_sec() + server_config.auto_time;
 129                         continue;
 130                 }
 131                 if (retval < 0 && errno != EINTR) {
 132                         DEBUG("error on select");
 133                         continue;
 134                 }
 135
 136                 switch (udhcp_sp_read(&rfds)) {
 137                 case SIGUSR1:
 138                         bb_info_msg("Received a SIGUSR1");
 139                         write_leases();
 140                         /* why not just reset the timeout, eh */
 141                         timeout_end = monotonic_sec() + server_config.auto_time;
 142                         continue;
 143                 case SIGTERM:
 144                         bb_info_msg("Received a SIGTERM");
 145                         goto ret0;
 146                 case 0: break;          /* no signal */
 147                 default: continue;      /* signal or error (probably EINTR) */
 148                 }
 149
 150                 bytes = udhcp_recv_kernel_packet(&packet, server_socket); /* this waits for a packet - idle */
 151                 if (bytes < 0) {
 152                         if (bytes == -1 && errno != EINTR) {
 153                                 DEBUG("error on read, %s, reopening socket", strerror(errno));
 154                                 close(server_socket);
 155                                 server_socket = -1;
 156                         }
 157                         continue;
 158                 }
 159
 160                 state = get_option(&packet, DHCP_MESSAGE_TYPE);
 161                 if (state == NULL) {
 162                         bb_error_msg("cannot get option from packet, ignoring");
 163                         continue;
 164                 }
 165
 166                 /* Look for a static lease */
 167                 static_lease_ip = getIpByMac(server_config.static_leases, &packet.chaddr);
 168
 169                 if (static_lease_ip) {
 170                         bb_info_msg("Found static lease: %x", static_lease_ip);
 171
 172                         memcpy(&static_lease.chaddr, &packet.chaddr, 16);
 173                         static_lease.yiaddr = static_lease_ip;
 174                         static_lease.expires = 0;
 175
 176                         lease = &static_lease;
 177                 } else {
 178                         lease = find_lease_by_chaddr(packet.chaddr);
 179                 }
 180
 181                 switch (state[0]) {
 182                 case DHCPDISCOVER:
 183                         DEBUG("Received DISCOVER");
 184
 185                         if (send_offer(&packet) < 0) {
 186                                 bb_error_msg("send OFFER failed");
 187                         }
 188                         break;
 189                 case DHCPREQUEST:
 190                         DEBUG("received REQUEST");
 191
 192                         requested = get_option(&packet, DHCP_REQUESTED_IP);
 193                         server_id = get_option(&packet, DHCP_SERVER_ID);
 194
 195                         if (requested)
 196                                 move_from_unaligned32(requested_aligned, requested);
 197                         if (server_id)
 198                                 move_from_unaligned32(server_id_aligned, server_id);
 199
 200                         if (lease) {
 201                                 if (server_id) {
 202                                         /* SELECTING State */
 203                                         DEBUG("server_id = %08x", ntohl(server_id_aligned));
 204                                         if (server_id_aligned == server_config.server
 205                                          && requested
 206                                          && requested_aligned == lease->yiaddr
 207                                         ) {
 208                                                 send_ACK(&packet, lease->yiaddr);
 209                                         }
 210                                 } else if (requested) {
 211                                         /* INIT-REBOOT State */
 212                                         if (lease->yiaddr == requested_aligned)
 213                                                 send_ACK(&packet, lease->yiaddr);
 214                                         else
 215                                                 send_NAK(&packet);
 216                                 } else if (lease->yiaddr == packet.ciaddr) {
 217                                         /* RENEWING or REBINDING State */
 218                                         send_ACK(&packet, lease->yiaddr);
 219                                 } else { /* don't know what to do!!!! */
 220                                         send_NAK(&packet);
 221                                 }
 222
 223                         /* what to do if we have no record of the client */
 224                         } else if (server_id) {
 225                                 /* SELECTING State */
 226
 227                         } else if (requested) {
 228                                 /* INIT-REBOOT State */
 229                                 lease = find_lease_by_yiaddr(requested_aligned);
 230                                 if (lease) {
 231                                         if (lease_expired(lease)) {
 232                                                 /* probably best if we drop this lease */
 233                                                 memset(lease->chaddr, 0, 16);
 234                                         /* make some contention for this address */
 235                                         } else
 236                                                 send_NAK(&packet);
 237                                 } else {
 238                                         uint32_t r = ntohl(requested_aligned);
 239                                         if (r < server_config.start_ip
 240                                          || r > server_config.end_ip
 241                                         ) {
 242                                                 send_NAK(&packet);
 243                                         }
 244                                         /* else remain silent */
 245                                 }
 246
 247                         } else {
 248                                 /* RENEWING or REBINDING State */
 249                         }
 250                         break;
 251                 case DHCPDECLINE:
 252                         DEBUG("Received DECLINE");
 253                         if (lease) {
 254                                 memset(lease->chaddr, 0, 16);
 255                                 lease->expires = time(0) + server_config.decline_time;
 256                         }
 257                         break;
 258                 case DHCPRELEASE:
 259                         DEBUG("Received RELEASE");
 260                         if (lease)
 261                                 lease->expires = time(0);
 262                         break;
 263                 case DHCPINFORM:
 264                         DEBUG("Received INFORM");
 265                         send_inform(&packet);
 266                         break;
 267                 default:
 268                         bb_info_msg("Unsupported DHCP message (%02x) - ignoring", state[0]);
 269                 }
 270         }
 271  ret0:
 272         retval = 0;
 273  ret:
 274         /*if (server_config.pidfile) - server_config.pidfile is never NULL */
 275                 remove_pidfile(server_config.pidfile);
 276         return retval;
 277 }