1 /* vi: set sw=4 ts=4: */
4 * Copyright (C) 1999 Matthew Ramsay <matthewr@moreton.com.au>
5 * Chris Trew <ctrew@moreton.com.au>
7 * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU General Public License for more details.
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 //usage:#define udhcpd_trivial_usage
25 //usage: "[-fS]" IF_FEATURE_UDHCP_PORT(" [-P N]") " [CONFFILE]"
26 //usage:#define udhcpd_full_usage "\n\n"
27 //usage: "DHCP server\n"
28 //usage: "\n -f Run in foreground"
29 //usage: "\n -S Log to syslog too"
30 //usage: IF_FEATURE_UDHCP_PORT(
31 //usage: "\n -P N Use port N (default 67)"
40 /* Send a packet to a specific mac address and ip address by creating our own ip packet */
41 static void send_packet_to_client(struct dhcp_packet *dhcp_pkt, int force_broadcast)
43 const uint8_t *chaddr;
47 //if (force_broadcast) { /* broadcast */ }
48 //else if (dhcp_pkt->ciaddr) { /* unicast to dhcp_pkt->ciaddr */ }
49 //else if (dhcp_pkt->flags & htons(BROADCAST_FLAG)) { /* broadcast */ }
50 //else { /* unicast to dhcp_pkt->yiaddr */ }
51 // But this is wrong: yiaddr is _our_ idea what client's IP is
52 // (for example, from lease file). Client may not know that,
53 // and may not have UDP socket listening on that IP!
54 // We should never unicast to dhcp_pkt->yiaddr!
55 // dhcp_pkt->ciaddr, OTOH, comes from client's request packet,
59 || (dhcp_pkt->flags & htons(BROADCAST_FLAG))
60 || dhcp_pkt->ciaddr == 0
62 log1("Broadcasting packet to client");
63 ciaddr = INADDR_BROADCAST;
64 chaddr = MAC_BCAST_ADDR;
66 log1("Unicasting packet to client ciaddr");
67 ciaddr = dhcp_pkt->ciaddr;
68 chaddr = dhcp_pkt->chaddr;
71 udhcp_send_raw_packet(dhcp_pkt,
72 /*src*/ server_config.server_nip, SERVER_PORT,
73 /*dst*/ ciaddr, CLIENT_PORT, chaddr,
74 server_config.ifindex);
77 /* Send a packet to gateway_nip using the kernel ip stack */
78 static void send_packet_to_relay(struct dhcp_packet *dhcp_pkt)
80 log1("Forwarding packet to relay");
82 udhcp_send_kernel_packet(dhcp_pkt,
83 server_config.server_nip, SERVER_PORT,
84 dhcp_pkt->gateway_nip, SERVER_PORT);
87 static void send_packet(struct dhcp_packet *dhcp_pkt, int force_broadcast)
89 if (dhcp_pkt->gateway_nip)
90 send_packet_to_relay(dhcp_pkt);
92 send_packet_to_client(dhcp_pkt, force_broadcast);
95 static void init_packet(struct dhcp_packet *packet, struct dhcp_packet *oldpacket, char type)
97 /* Sets op, htype, hlen, cookie fields
98 * and adds DHCP_MESSAGE_TYPE option */
99 udhcp_init_header(packet, type);
101 packet->xid = oldpacket->xid;
102 memcpy(packet->chaddr, oldpacket->chaddr, sizeof(oldpacket->chaddr));
103 packet->flags = oldpacket->flags;
104 packet->gateway_nip = oldpacket->gateway_nip;
105 packet->ciaddr = oldpacket->ciaddr;
106 udhcp_add_simple_option(packet, DHCP_SERVER_ID, server_config.server_nip);
109 /* Fill options field, siaddr_nip, and sname and boot_file fields.
110 * TODO: teach this code to use overload option.
112 static void add_server_options(struct dhcp_packet *packet)
114 struct option_set *curr = server_config.options;
117 if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
118 udhcp_add_binary_option(packet, curr->data);
122 packet->siaddr_nip = server_config.siaddr_nip;
124 if (server_config.sname)
125 strncpy((char*)packet->sname, server_config.sname, sizeof(packet->sname) - 1);
126 if (server_config.boot_file)
127 strncpy((char*)packet->file, server_config.boot_file, sizeof(packet->file) - 1);
130 static uint32_t select_lease_time(struct dhcp_packet *packet)
132 uint32_t lease_time_sec = server_config.max_lease_sec;
133 uint8_t *lease_time_opt = udhcp_get_option(packet, DHCP_LEASE_TIME);
134 if (lease_time_opt) {
135 move_from_unaligned32(lease_time_sec, lease_time_opt);
136 lease_time_sec = ntohl(lease_time_sec);
137 if (lease_time_sec > server_config.max_lease_sec)
138 lease_time_sec = server_config.max_lease_sec;
139 if (lease_time_sec < server_config.min_lease_sec)
140 lease_time_sec = server_config.min_lease_sec;
142 return lease_time_sec;
145 /* We got a DHCP DISCOVER. Send an OFFER. */
146 /* NOINLINE: limit stack usage in caller */
147 static NOINLINE void send_offer(struct dhcp_packet *oldpacket,
148 uint32_t static_lease_nip,
149 struct dyn_lease *lease,
150 uint8_t *requested_ip_opt)
152 struct dhcp_packet packet;
153 uint32_t lease_time_sec;
156 init_packet(&packet, oldpacket, DHCPOFFER);
158 /* If it is a static lease, use its IP */
159 packet.yiaddr = static_lease_nip;
161 if (!static_lease_nip) {
162 /* We have no static lease for client's chaddr */
164 const char *p_host_name;
167 /* We have a dynamic lease for client's chaddr.
168 * Reuse its IP (even if lease is expired).
169 * Note that we ignore requested IP in this case.
171 packet.yiaddr = lease->lease_nip;
173 /* Or: if client has requested an IP */
174 else if (requested_ip_opt != NULL
176 && (move_from_unaligned32(req_nip, requested_ip_opt), 1)
177 /* and the IP is in the lease range */
178 && ntohl(req_nip) >= server_config.start_ip
179 && ntohl(req_nip) <= server_config.end_ip
181 && ( !(lease = find_lease_by_nip(req_nip)) /* is not already taken */
182 || is_expired_lease(lease) /* or is taken, but expired */
185 packet.yiaddr = req_nip;
188 /* Otherwise, find a free IP */
189 packet.yiaddr = find_free_or_expired_nip(oldpacket->chaddr);
192 if (!packet.yiaddr) {
193 bb_error_msg("no free IP addresses. OFFER abandoned");
196 /* Reserve the IP for a short time hoping to get DHCPREQUEST soon */
197 p_host_name = (const char*) udhcp_get_option(oldpacket, DHCP_HOST_NAME);
198 lease = add_lease(packet.chaddr, packet.yiaddr,
199 server_config.offer_time,
201 p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
204 bb_error_msg("no free IP addresses. OFFER abandoned");
209 lease_time_sec = select_lease_time(oldpacket);
210 udhcp_add_simple_option(&packet, DHCP_LEASE_TIME, htonl(lease_time_sec));
211 add_server_options(&packet);
213 addr.s_addr = packet.yiaddr;
214 bb_info_msg("Sending OFFER of %s", inet_ntoa(addr));
215 /* send_packet emits error message itself if it detects failure */
216 send_packet(&packet, /*force_bcast:*/ 0);
219 /* NOINLINE: limit stack usage in caller */
220 static NOINLINE void send_NAK(struct dhcp_packet *oldpacket)
222 struct dhcp_packet packet;
224 init_packet(&packet, oldpacket, DHCPNAK);
227 send_packet(&packet, /*force_bcast:*/ 1);
230 /* NOINLINE: limit stack usage in caller */
231 static NOINLINE void send_ACK(struct dhcp_packet *oldpacket, uint32_t yiaddr)
233 struct dhcp_packet packet;
234 uint32_t lease_time_sec;
236 const char *p_host_name;
238 init_packet(&packet, oldpacket, DHCPACK);
239 packet.yiaddr = yiaddr;
241 lease_time_sec = select_lease_time(oldpacket);
242 udhcp_add_simple_option(&packet, DHCP_LEASE_TIME, htonl(lease_time_sec));
244 add_server_options(&packet);
246 addr.s_addr = yiaddr;
247 bb_info_msg("Sending ACK to %s", inet_ntoa(addr));
248 send_packet(&packet, /*force_bcast:*/ 0);
250 p_host_name = (const char*) udhcp_get_option(oldpacket, DHCP_HOST_NAME);
251 add_lease(packet.chaddr, packet.yiaddr,
254 p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
256 if (ENABLE_FEATURE_UDHCPD_WRITE_LEASES_EARLY) {
257 /* rewrite the file with leases at every new acceptance */
262 /* NOINLINE: limit stack usage in caller */
263 static NOINLINE void send_inform(struct dhcp_packet *oldpacket)
265 struct dhcp_packet packet;
267 /* "If a client has obtained a network address through some other means
268 * (e.g., manual configuration), it may use a DHCPINFORM request message
269 * to obtain other local configuration parameters. Servers receiving a
270 * DHCPINFORM message construct a DHCPACK message with any local
271 * configuration parameters appropriate for the client without:
272 * allocating a new address, checking for an existing binding, filling
273 * in 'yiaddr' or including lease time parameters. The servers SHOULD
274 * unicast the DHCPACK reply to the address given in the 'ciaddr' field
275 * of the DHCPINFORM message.
277 * The server responds to a DHCPINFORM message by sending a DHCPACK
278 * message directly to the address given in the 'ciaddr' field
279 * of the DHCPINFORM message. The server MUST NOT send a lease
280 * expiration time to the client and SHOULD NOT fill in 'yiaddr'."
282 //TODO: do a few sanity checks: is ciaddr set?
283 //Better yet: is ciaddr == IP source addr?
284 init_packet(&packet, oldpacket, DHCPACK);
285 add_server_options(&packet);
287 send_packet(&packet, /*force_bcast:*/ 0);
292 struct dyn_lease *g_leases;
293 /* struct server_config_t server_config is in bb_common_bufsiz1 */
296 int udhcpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
297 int udhcpd_main(int argc UNUSED_PARAM, char **argv)
299 int server_socket = -1, retval, max_sock;
301 unsigned timeout_end;
304 struct option_set *option;
305 IF_FEATURE_UDHCP_PORT(char *str_P;)
307 #if ENABLE_FEATURE_UDHCP_PORT
312 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
313 opt_complementary = "vv";
315 opt = getopt32(argv, "fSv"
316 IF_FEATURE_UDHCP_PORT("P:", &str_P)
317 IF_UDHCP_VERBOSE(, &dhcp_verbose)
319 if (!(opt & 1)) { /* no -f */
320 bb_daemonize_or_rexec(0, argv);
321 logmode = LOGMODE_NONE;
323 /* update argv after the possible vfork+exec in daemonize */
325 if (opt & 2) { /* -S */
326 openlog(applet_name, LOG_PID, LOG_DAEMON);
327 logmode |= LOGMODE_SYSLOG;
329 #if ENABLE_FEATURE_UDHCP_PORT
330 if (opt & 8) { /* -P */
331 SERVER_PORT = xatou16(str_P);
332 CLIENT_PORT = SERVER_PORT + 1;
335 /* Would rather not do read_config before daemonization -
336 * otherwise NOMMU machines will parse config twice */
337 read_config(argv[0] ? argv[0] : DHCPD_CONF_FILE);
339 /* Make sure fd 0,1,2 are open */
341 /* Equivalent of doing a fflush after every \n */
345 write_pidfile(server_config.pidfile);
346 /* if (!..) bb_perror_msg("can't create pidfile %s", pidfile); */
348 bb_info_msg("%s (v"BB_VER") started", applet_name);
350 option = udhcp_find_option(server_config.options, DHCP_LEASE_TIME);
351 server_config.max_lease_sec = DEFAULT_LEASE_TIME;
353 move_from_unaligned32(server_config.max_lease_sec, option->data + OPT_DATA);
354 server_config.max_lease_sec = ntohl(server_config.max_lease_sec);
358 num_ips = server_config.end_ip - server_config.start_ip + 1;
359 if (server_config.max_leases > num_ips) {
360 bb_error_msg("max_leases=%u is too big, setting to %u",
361 (unsigned)server_config.max_leases, num_ips);
362 server_config.max_leases = num_ips;
365 g_leases = xzalloc(server_config.max_leases * sizeof(g_leases[0]));
366 read_leases(server_config.lease_file);
368 if (udhcp_read_interface(server_config.interface,
369 &server_config.ifindex,
370 &server_config.server_nip,
371 server_config.server_mac)
377 /* Setup the signal pipe */
380 continue_with_autotime:
381 timeout_end = monotonic_sec() + server_config.auto_time;
382 while (1) { /* loop until universe collapses */
384 struct dhcp_packet packet;
387 uint8_t *server_id_opt;
388 uint8_t *requested_ip_opt;
389 uint32_t requested_nip = requested_nip; /* for compiler */
390 uint32_t static_lease_nip;
391 struct dyn_lease *lease, fake_lease;
393 if (server_socket < 0) {
394 server_socket = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT,
395 server_config.interface);
398 max_sock = udhcp_sp_fd_set(&rfds, server_socket);
399 if (server_config.auto_time) {
400 tv.tv_sec = timeout_end - monotonic_sec();
404 if (!server_config.auto_time || tv.tv_sec > 0) {
405 retval = select(max_sock + 1, &rfds, NULL, NULL,
406 server_config.auto_time ? &tv : NULL);
410 goto continue_with_autotime;
412 if (retval < 0 && errno != EINTR) {
413 log1("Error on select");
417 switch (udhcp_sp_read(&rfds)) {
419 bb_info_msg("Received SIGUSR1");
421 /* why not just reset the timeout, eh */
422 goto continue_with_autotime;
424 bb_info_msg("Received SIGTERM");
427 case 0: /* no signal: read a packet */
429 default: /* signal or error (probably EINTR): back to select */
433 bytes = udhcp_recv_kernel_packet(&packet, server_socket);
435 /* bytes can also be -2 ("bad packet data") */
436 if (bytes == -1 && errno != EINTR) {
437 log1("Read error: %s, reopening socket", strerror(errno));
438 close(server_socket);
443 if (packet.hlen != 6) {
444 bb_error_msg("MAC length != 6, ignoring packet");
447 if (packet.op != BOOTREQUEST) {
448 bb_error_msg("not a REQUEST, ignoring packet");
451 state = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
452 if (state == NULL || state[0] < DHCP_MINTYPE || state[0] > DHCP_MAXTYPE) {
453 bb_error_msg("no or bad message type option, ignoring packet");
457 /* Get SERVER_ID if present */
458 server_id_opt = udhcp_get_option(&packet, DHCP_SERVER_ID);
460 uint32_t server_id_network_order;
461 move_from_unaligned32(server_id_network_order, server_id_opt);
462 if (server_id_network_order != server_config.server_nip) {
463 /* client talks to somebody else */
464 log1("server ID doesn't match, ignoring");
469 /* Look for a static/dynamic lease */
470 static_lease_nip = get_static_nip_by_mac(server_config.static_leases, &packet.chaddr);
471 if (static_lease_nip) {
472 bb_info_msg("Found static lease: %x", static_lease_nip);
473 memcpy(&fake_lease.lease_mac, &packet.chaddr, 6);
474 fake_lease.lease_nip = static_lease_nip;
475 fake_lease.expires = 0;
478 lease = find_lease_by_mac(packet.chaddr);
481 /* Get REQUESTED_IP if present */
482 requested_ip_opt = udhcp_get_option(&packet, DHCP_REQUESTED_IP);
483 if (requested_ip_opt) {
484 move_from_unaligned32(requested_nip, requested_ip_opt);
490 log1("Received DISCOVER");
492 send_offer(&packet, static_lease_nip, lease, requested_ip_opt);
496 log1("Received REQUEST");
499 o DHCPREQUEST generated during SELECTING state:
501 Client inserts the address of the selected server in 'server
502 identifier', 'ciaddr' MUST be zero, 'requested IP address' MUST be
503 filled in with the yiaddr value from the chosen DHCPOFFER.
505 Note that the client may choose to collect several DHCPOFFER
506 messages and select the "best" offer. The client indicates its
507 selection by identifying the offering server in the DHCPREQUEST
508 message. If the client receives no acceptable offers, the client
509 may choose to try another DHCPDISCOVER message. Therefore, the
510 servers may not receive a specific DHCPREQUEST from which they can
511 decide whether or not the client has accepted the offer.
513 o DHCPREQUEST generated during INIT-REBOOT state:
515 'server identifier' MUST NOT be filled in, 'requested IP address'
516 option MUST be filled in with client's notion of its previously
517 assigned address. 'ciaddr' MUST be zero. The client is seeking to
518 verify a previously allocated, cached configuration. Server SHOULD
519 send a DHCPNAK message to the client if the 'requested IP address'
520 is incorrect, or is on the wrong network.
522 Determining whether a client in the INIT-REBOOT state is on the
523 correct network is done by examining the contents of 'giaddr', the
524 'requested IP address' option, and a database lookup. If the DHCP
525 server detects that the client is on the wrong net (i.e., the
526 result of applying the local subnet mask or remote subnet mask (if
527 'giaddr' is not zero) to 'requested IP address' option value
528 doesn't match reality), then the server SHOULD send a DHCPNAK
529 message to the client.
531 If the network is correct, then the DHCP server should check if
532 the client's notion of its IP address is correct. If not, then the
533 server SHOULD send a DHCPNAK message to the client. If the DHCP
534 server has no record of this client, then it MUST remain silent,
535 and MAY output a warning to the network administrator. This
536 behavior is necessary for peaceful coexistence of non-
537 communicating DHCP servers on the same wire.
539 If 'giaddr' is 0x0 in the DHCPREQUEST message, the client is on
540 the same subnet as the server. The server MUST broadcast the
541 DHCPNAK message to the 0xffffffff broadcast address because the
542 client may not have a correct network address or subnet mask, and
543 the client may not be answering ARP requests.
545 If 'giaddr' is set in the DHCPREQUEST message, the client is on a
546 different subnet. The server MUST set the broadcast bit in the
547 DHCPNAK, so that the relay agent will broadcast the DHCPNAK to the
548 client, because the client may not have a correct network address
549 or subnet mask, and the client may not be answering ARP requests.
551 o DHCPREQUEST generated during RENEWING state:
553 'server identifier' MUST NOT be filled in, 'requested IP address'
554 option MUST NOT be filled in, 'ciaddr' MUST be filled in with
555 client's IP address. In this situation, the client is completely
556 configured, and is trying to extend its lease. This message will
557 be unicast, so no relay agents will be involved in its
558 transmission. Because 'giaddr' is therefore not filled in, the
559 DHCP server will trust the value in 'ciaddr', and use it when
560 replying to the client.
562 A client MAY choose to renew or extend its lease prior to T1. The
563 server may choose not to extend the lease (as a policy decision by
564 the network administrator), but should return a DHCPACK message
567 o DHCPREQUEST generated during REBINDING state:
569 'server identifier' MUST NOT be filled in, 'requested IP address'
570 option MUST NOT be filled in, 'ciaddr' MUST be filled in with
571 client's IP address. In this situation, the client is completely
572 configured, and is trying to extend its lease. This message MUST
573 be broadcast to the 0xffffffff IP broadcast address. The DHCP
574 server SHOULD check 'ciaddr' for correctness before replying to
577 The DHCPREQUEST from a REBINDING client is intended to accommodate
578 sites that have multiple DHCP servers and a mechanism for
579 maintaining consistency among leases managed by multiple servers.
580 A DHCP server MAY extend a client's lease only if it has local
581 administrative authority to do so.
583 if (!requested_ip_opt) {
584 requested_nip = packet.ciaddr;
585 if (requested_nip == 0) {
586 log1("no requested IP and no ciaddr, ignoring");
590 if (lease && requested_nip == lease->lease_nip) {
591 /* client requested or configured IP matches the lease.
592 * ACK it, and bump lease expiration time. */
593 send_ACK(&packet, lease->lease_nip);
596 /* No lease for this MAC, or lease IP != requested IP */
598 if (server_id_opt /* client is in SELECTING state */
599 || requested_ip_opt /* client is in INIT-REBOOT state */
601 /* "No, we don't have this IP for you" */
603 } /* else: client is in RENEWING or REBINDING, do not answer */
609 * "If the server receives a DHCPDECLINE message,
610 * the client has discovered through some other means
611 * that the suggested network address is already
612 * in use. The server MUST mark the network address
613 * as not available and SHOULD notify the local
614 * sysadmin of a possible configuration problem."
616 * SERVER_ID must be present,
617 * REQUESTED_IP must be present,
618 * chaddr must be filled in,
619 * ciaddr must be 0 (we do not check this)
621 log1("Received DECLINE");
624 && lease /* chaddr matches this lease */
625 && requested_nip == lease->lease_nip
627 memset(lease->lease_mac, 0, sizeof(lease->lease_mac));
628 lease->expires = time(NULL) + server_config.decline_time;
633 /* "Upon receipt of a DHCPRELEASE message, the server
634 * marks the network address as not allocated."
636 * SERVER_ID must be present,
637 * REQUESTED_IP must not be present (we do not check this),
638 * chaddr must be filled in,
639 * ciaddr must be filled in
641 log1("Received RELEASE");
643 && lease /* chaddr matches this lease */
644 && packet.ciaddr == lease->lease_nip
646 lease->expires = time(NULL);
651 log1("Received INFORM");
652 send_inform(&packet);
659 /*if (server_config.pidfile) - server_config.pidfile is never NULL */
660 remove_pidfile(server_config.pidfile);