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] [-I ADDR]" 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: "\n -I ADDR Local address"
31 //usage: "\n -a MSEC Timeout for ARP ping (default 2000)"
32 //usage: IF_FEATURE_UDHCP_PORT(
33 //usage: "\n -P N Use port N (default 67)"
42 /* Send a packet to a specific mac address and ip address by creating our own ip packet */
43 static void send_packet_to_client(struct dhcp_packet
*dhcp_pkt
, int force_broadcast
)
45 const uint8_t *chaddr
;
49 //if (force_broadcast) { /* broadcast */ }
50 //else if (dhcp_pkt->ciaddr) { /* unicast to dhcp_pkt->ciaddr */ }
51 //else if (dhcp_pkt->flags & htons(BROADCAST_FLAG)) { /* broadcast */ }
52 //else { /* unicast to dhcp_pkt->yiaddr */ }
53 // But this is wrong: yiaddr is _our_ idea what client's IP is
54 // (for example, from lease file). Client may not know that,
55 // and may not have UDP socket listening on that IP!
56 // We should never unicast to dhcp_pkt->yiaddr!
57 // dhcp_pkt->ciaddr, OTOH, comes from client's request packet,
61 || (dhcp_pkt
->flags
& htons(BROADCAST_FLAG
))
62 || dhcp_pkt
->ciaddr
== 0
64 log1("Broadcasting packet to client");
65 ciaddr
= INADDR_BROADCAST
;
66 chaddr
= MAC_BCAST_ADDR
;
68 log1("Unicasting packet to client ciaddr");
69 ciaddr
= dhcp_pkt
->ciaddr
;
70 chaddr
= dhcp_pkt
->chaddr
;
73 udhcp_send_raw_packet(dhcp_pkt
,
74 /*src*/ server_config
.server_nip
, SERVER_PORT
,
75 /*dst*/ ciaddr
, CLIENT_PORT
, chaddr
,
76 server_config
.ifindex
);
79 /* Send a packet to gateway_nip using the kernel ip stack */
80 static void send_packet_to_relay(struct dhcp_packet
*dhcp_pkt
)
82 log1("Forwarding packet to relay");
84 udhcp_send_kernel_packet(dhcp_pkt
,
85 server_config
.server_nip
, SERVER_PORT
,
86 dhcp_pkt
->gateway_nip
, SERVER_PORT
);
89 static void send_packet(struct dhcp_packet
*dhcp_pkt
, int force_broadcast
)
91 if (dhcp_pkt
->gateway_nip
)
92 send_packet_to_relay(dhcp_pkt
);
94 send_packet_to_client(dhcp_pkt
, force_broadcast
);
97 static void init_packet(struct dhcp_packet
*packet
, struct dhcp_packet
*oldpacket
, char type
)
99 /* Sets op, htype, hlen, cookie fields
100 * and adds DHCP_MESSAGE_TYPE option */
101 udhcp_init_header(packet
, type
);
103 packet
->xid
= oldpacket
->xid
;
104 memcpy(packet
->chaddr
, oldpacket
->chaddr
, sizeof(oldpacket
->chaddr
));
105 packet
->flags
= oldpacket
->flags
;
106 packet
->gateway_nip
= oldpacket
->gateway_nip
;
107 packet
->ciaddr
= oldpacket
->ciaddr
;
108 udhcp_add_simple_option(packet
, DHCP_SERVER_ID
, server_config
.server_nip
);
111 /* Fill options field, siaddr_nip, and sname and boot_file fields.
112 * TODO: teach this code to use overload option.
114 static void add_server_options(struct dhcp_packet
*packet
)
116 struct option_set
*curr
= server_config
.options
;
119 if (curr
->data
[OPT_CODE
] != DHCP_LEASE_TIME
)
120 udhcp_add_binary_option(packet
, curr
->data
);
124 packet
->siaddr_nip
= server_config
.siaddr_nip
;
126 if (server_config
.sname
)
127 strncpy((char*)packet
->sname
, server_config
.sname
, sizeof(packet
->sname
) - 1);
128 if (server_config
.boot_file
)
129 strncpy((char*)packet
->file
, server_config
.boot_file
, sizeof(packet
->file
) - 1);
132 static uint32_t select_lease_time(struct dhcp_packet
*packet
)
134 uint32_t lease_time_sec
= server_config
.max_lease_sec
;
135 uint8_t *lease_time_opt
= udhcp_get_option(packet
, DHCP_LEASE_TIME
);
136 if (lease_time_opt
) {
137 move_from_unaligned32(lease_time_sec
, lease_time_opt
);
138 lease_time_sec
= ntohl(lease_time_sec
);
139 if (lease_time_sec
> server_config
.max_lease_sec
)
140 lease_time_sec
= server_config
.max_lease_sec
;
141 if (lease_time_sec
< server_config
.min_lease_sec
)
142 lease_time_sec
= server_config
.min_lease_sec
;
144 return lease_time_sec
;
147 /* We got a DHCP DISCOVER. Send an OFFER. */
148 /* NOINLINE: limit stack usage in caller */
149 static NOINLINE
void send_offer(struct dhcp_packet
*oldpacket
,
150 uint32_t static_lease_nip
,
151 struct dyn_lease
*lease
,
152 uint8_t *requested_ip_opt
,
155 struct dhcp_packet packet
;
156 uint32_t lease_time_sec
;
159 init_packet(&packet
, oldpacket
, DHCPOFFER
);
161 /* If it is a static lease, use its IP */
162 packet
.yiaddr
= static_lease_nip
;
164 if (!static_lease_nip
) {
165 /* We have no static lease for client's chaddr */
167 const char *p_host_name
;
170 /* We have a dynamic lease for client's chaddr.
171 * Reuse its IP (even if lease is expired).
172 * Note that we ignore requested IP in this case.
174 packet
.yiaddr
= lease
->lease_nip
;
176 /* Or: if client has requested an IP */
177 else if (requested_ip_opt
!= NULL
179 && (move_from_unaligned32(req_nip
, requested_ip_opt
), 1)
180 /* and the IP is in the lease range */
181 && ntohl(req_nip
) >= server_config
.start_ip
182 && ntohl(req_nip
) <= server_config
.end_ip
184 && ( !(lease
= find_lease_by_nip(req_nip
)) /* is not already taken */
185 || is_expired_lease(lease
) /* or is taken, but expired */
188 packet
.yiaddr
= req_nip
;
191 /* Otherwise, find a free IP */
192 packet
.yiaddr
= find_free_or_expired_nip(oldpacket
->chaddr
, arpping_ms
);
195 if (!packet
.yiaddr
) {
196 bb_error_msg("no free IP addresses. OFFER abandoned");
199 /* Reserve the IP for a short time hoping to get DHCPREQUEST soon */
200 p_host_name
= (const char*) udhcp_get_option(oldpacket
, DHCP_HOST_NAME
);
201 lease
= add_lease(packet
.chaddr
, packet
.yiaddr
,
202 server_config
.offer_time
,
204 p_host_name
? (unsigned char)p_host_name
[OPT_LEN
- OPT_DATA
] : 0
207 bb_error_msg("no free IP addresses. OFFER abandoned");
212 lease_time_sec
= select_lease_time(oldpacket
);
213 udhcp_add_simple_option(&packet
, DHCP_LEASE_TIME
, htonl(lease_time_sec
));
214 add_server_options(&packet
);
216 addr
.s_addr
= packet
.yiaddr
;
217 bb_info_msg("Sending OFFER of %s", inet_ntoa(addr
));
218 /* send_packet emits error message itself if it detects failure */
219 send_packet(&packet
, /*force_bcast:*/ 0);
222 /* NOINLINE: limit stack usage in caller */
223 static NOINLINE
void send_NAK(struct dhcp_packet
*oldpacket
)
225 struct dhcp_packet packet
;
227 init_packet(&packet
, oldpacket
, DHCPNAK
);
230 send_packet(&packet
, /*force_bcast:*/ 1);
233 /* NOINLINE: limit stack usage in caller */
234 static NOINLINE
void send_ACK(struct dhcp_packet
*oldpacket
, uint32_t yiaddr
)
236 struct dhcp_packet packet
;
237 uint32_t lease_time_sec
;
239 const char *p_host_name
;
241 init_packet(&packet
, oldpacket
, DHCPACK
);
242 packet
.yiaddr
= yiaddr
;
244 lease_time_sec
= select_lease_time(oldpacket
);
245 udhcp_add_simple_option(&packet
, DHCP_LEASE_TIME
, htonl(lease_time_sec
));
247 add_server_options(&packet
);
249 addr
.s_addr
= yiaddr
;
250 bb_info_msg("Sending ACK to %s", inet_ntoa(addr
));
251 send_packet(&packet
, /*force_bcast:*/ 0);
253 p_host_name
= (const char*) udhcp_get_option(oldpacket
, DHCP_HOST_NAME
);
254 add_lease(packet
.chaddr
, packet
.yiaddr
,
257 p_host_name
? (unsigned char)p_host_name
[OPT_LEN
- OPT_DATA
] : 0
259 if (ENABLE_FEATURE_UDHCPD_WRITE_LEASES_EARLY
) {
260 /* rewrite the file with leases at every new acceptance */
265 /* NOINLINE: limit stack usage in caller */
266 static NOINLINE
void send_inform(struct dhcp_packet
*oldpacket
)
268 struct dhcp_packet packet
;
270 /* "If a client has obtained a network address through some other means
271 * (e.g., manual configuration), it may use a DHCPINFORM request message
272 * to obtain other local configuration parameters. Servers receiving a
273 * DHCPINFORM message construct a DHCPACK message with any local
274 * configuration parameters appropriate for the client without:
275 * allocating a new address, checking for an existing binding, filling
276 * in 'yiaddr' or including lease time parameters. The servers SHOULD
277 * unicast the DHCPACK reply to the address given in the 'ciaddr' field
278 * of the DHCPINFORM message.
280 * The server responds to a DHCPINFORM message by sending a DHCPACK
281 * message directly to the address given in the 'ciaddr' field
282 * of the DHCPINFORM message. The server MUST NOT send a lease
283 * expiration time to the client and SHOULD NOT fill in 'yiaddr'."
285 //TODO: do a few sanity checks: is ciaddr set?
286 //Better yet: is ciaddr == IP source addr?
287 init_packet(&packet
, oldpacket
, DHCPACK
);
288 add_server_options(&packet
);
290 send_packet(&packet
, /*force_bcast:*/ 0);
295 struct dyn_lease
*g_leases
;
296 /* struct server_config_t server_config is in bb_common_bufsiz1 */
299 int udhcpd_main(int argc
, char **argv
) MAIN_EXTERNALLY_VISIBLE
;
300 int udhcpd_main(int argc UNUSED_PARAM
, char **argv
)
302 int server_socket
= -1, retval
, max_sock
;
304 unsigned timeout_end
;
307 struct option_set
*option
;
309 const char *str_a
= "2000";
311 IF_FEATURE_UDHCP_PORT(char *str_P
;)
313 #if ENABLE_FEATURE_UDHCP_PORT
318 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
319 opt_complementary
= "vv";
321 opt
= getopt32(argv
, "fSI:va:"
322 IF_FEATURE_UDHCP_PORT("P:")
325 IF_FEATURE_UDHCP_PORT(, &str_P
)
326 IF_UDHCP_VERBOSE(, &dhcp_verbose
)
328 if (!(opt
& 1)) { /* no -f */
329 bb_daemonize_or_rexec(0, argv
);
330 logmode
= LOGMODE_NONE
;
332 /* update argv after the possible vfork+exec in daemonize */
334 if (opt
& 2) { /* -S */
335 openlog(applet_name
, LOG_PID
, LOG_DAEMON
);
336 logmode
|= LOGMODE_SYSLOG
;
338 if (opt
& 4) { /* -I */
339 len_and_sockaddr
*lsa
= xhost_and_af2sockaddr(str_I
, 0, AF_INET
);
340 server_config
.server_nip
= lsa
->u
.sin
.sin_addr
.s_addr
;
343 #if ENABLE_FEATURE_UDHCP_PORT
344 if (opt
& 32) { /* -P */
345 SERVER_PORT
= xatou16(str_P
);
346 CLIENT_PORT
= SERVER_PORT
+ 1;
349 arpping_ms
= xatou(str_a
);
351 /* Would rather not do read_config before daemonization -
352 * otherwise NOMMU machines will parse config twice */
353 read_config(argv
[0] ? argv
[0] : DHCPD_CONF_FILE
);
355 /* Make sure fd 0,1,2 are open */
357 /* Equivalent of doing a fflush after every \n */
361 write_pidfile(server_config
.pidfile
);
362 /* if (!..) bb_perror_msg("can't create pidfile %s", pidfile); */
364 bb_info_msg("%s (v"BB_VER
") started", applet_name
);
366 option
= udhcp_find_option(server_config
.options
, DHCP_LEASE_TIME
);
367 server_config
.max_lease_sec
= DEFAULT_LEASE_TIME
;
369 move_from_unaligned32(server_config
.max_lease_sec
, option
->data
+ OPT_DATA
);
370 server_config
.max_lease_sec
= ntohl(server_config
.max_lease_sec
);
374 num_ips
= server_config
.end_ip
- server_config
.start_ip
+ 1;
375 if (server_config
.max_leases
> num_ips
) {
376 bb_error_msg("max_leases=%u is too big, setting to %u",
377 (unsigned)server_config
.max_leases
, num_ips
);
378 server_config
.max_leases
= num_ips
;
381 g_leases
= xzalloc(server_config
.max_leases
* sizeof(g_leases
[0]));
382 read_leases(server_config
.lease_file
);
384 if (udhcp_read_interface(server_config
.interface
,
385 &server_config
.ifindex
,
386 (server_config
.server_nip
== 0 ? &server_config
.server_nip
: NULL
),
387 server_config
.server_mac
)
393 /* Setup the signal pipe */
396 continue_with_autotime
:
397 timeout_end
= monotonic_sec() + server_config
.auto_time
;
398 while (1) { /* loop until universe collapses */
400 struct dhcp_packet packet
;
403 uint8_t *server_id_opt
;
404 uint8_t *requested_ip_opt
;
405 uint32_t requested_nip
= requested_nip
; /* for compiler */
406 uint32_t static_lease_nip
;
407 struct dyn_lease
*lease
, fake_lease
;
409 if (server_socket
< 0) {
410 server_socket
= udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT
,
411 server_config
.interface
);
414 max_sock
= udhcp_sp_fd_set(&rfds
, server_socket
);
415 if (server_config
.auto_time
) {
416 tv
.tv_sec
= timeout_end
- monotonic_sec();
420 if (!server_config
.auto_time
|| tv
.tv_sec
> 0) {
421 retval
= select(max_sock
+ 1, &rfds
, NULL
, NULL
,
422 server_config
.auto_time
? &tv
: NULL
);
426 goto continue_with_autotime
;
428 if (retval
< 0 && errno
!= EINTR
) {
429 log1("Error on select");
433 switch (udhcp_sp_read(&rfds
)) {
435 bb_info_msg("Received SIGUSR1");
437 /* why not just reset the timeout, eh */
438 goto continue_with_autotime
;
440 bb_info_msg("Received SIGTERM");
443 case 0: /* no signal: read a packet */
445 default: /* signal or error (probably EINTR): back to select */
449 bytes
= udhcp_recv_kernel_packet(&packet
, server_socket
);
451 /* bytes can also be -2 ("bad packet data") */
452 if (bytes
== -1 && errno
!= EINTR
) {
453 log1("Read error: %s, reopening socket", strerror(errno
));
454 close(server_socket
);
459 if (packet
.hlen
!= 6) {
460 bb_error_msg("MAC length != 6, ignoring packet");
463 if (packet
.op
!= BOOTREQUEST
) {
464 bb_error_msg("not a REQUEST, ignoring packet");
467 state
= udhcp_get_option(&packet
, DHCP_MESSAGE_TYPE
);
468 if (state
== NULL
|| state
[0] < DHCP_MINTYPE
|| state
[0] > DHCP_MAXTYPE
) {
469 bb_error_msg("no or bad message type option, ignoring packet");
473 /* Get SERVER_ID if present */
474 server_id_opt
= udhcp_get_option(&packet
, DHCP_SERVER_ID
);
476 uint32_t server_id_network_order
;
477 move_from_unaligned32(server_id_network_order
, server_id_opt
);
478 if (server_id_network_order
!= server_config
.server_nip
) {
479 /* client talks to somebody else */
480 log1("server ID doesn't match, ignoring");
485 /* Look for a static/dynamic lease */
486 static_lease_nip
= get_static_nip_by_mac(server_config
.static_leases
, &packet
.chaddr
);
487 if (static_lease_nip
) {
488 bb_info_msg("Found static lease: %x", static_lease_nip
);
489 memcpy(&fake_lease
.lease_mac
, &packet
.chaddr
, 6);
490 fake_lease
.lease_nip
= static_lease_nip
;
491 fake_lease
.expires
= 0;
494 lease
= find_lease_by_mac(packet
.chaddr
);
497 /* Get REQUESTED_IP if present */
498 requested_ip_opt
= udhcp_get_option(&packet
, DHCP_REQUESTED_IP
);
499 if (requested_ip_opt
) {
500 move_from_unaligned32(requested_nip
, requested_ip_opt
);
506 log1("Received DISCOVER");
508 send_offer(&packet
, static_lease_nip
, lease
, requested_ip_opt
, arpping_ms
);
512 log1("Received REQUEST");
515 o DHCPREQUEST generated during SELECTING state:
517 Client inserts the address of the selected server in 'server
518 identifier', 'ciaddr' MUST be zero, 'requested IP address' MUST be
519 filled in with the yiaddr value from the chosen DHCPOFFER.
521 Note that the client may choose to collect several DHCPOFFER
522 messages and select the "best" offer. The client indicates its
523 selection by identifying the offering server in the DHCPREQUEST
524 message. If the client receives no acceptable offers, the client
525 may choose to try another DHCPDISCOVER message. Therefore, the
526 servers may not receive a specific DHCPREQUEST from which they can
527 decide whether or not the client has accepted the offer.
529 o DHCPREQUEST generated during INIT-REBOOT state:
531 'server identifier' MUST NOT be filled in, 'requested IP address'
532 option MUST be filled in with client's notion of its previously
533 assigned address. 'ciaddr' MUST be zero. The client is seeking to
534 verify a previously allocated, cached configuration. Server SHOULD
535 send a DHCPNAK message to the client if the 'requested IP address'
536 is incorrect, or is on the wrong network.
538 Determining whether a client in the INIT-REBOOT state is on the
539 correct network is done by examining the contents of 'giaddr', the
540 'requested IP address' option, and a database lookup. If the DHCP
541 server detects that the client is on the wrong net (i.e., the
542 result of applying the local subnet mask or remote subnet mask (if
543 'giaddr' is not zero) to 'requested IP address' option value
544 doesn't match reality), then the server SHOULD send a DHCPNAK
545 message to the client.
547 If the network is correct, then the DHCP server should check if
548 the client's notion of its IP address is correct. If not, then the
549 server SHOULD send a DHCPNAK message to the client. If the DHCP
550 server has no record of this client, then it MUST remain silent,
551 and MAY output a warning to the network administrator. This
552 behavior is necessary for peaceful coexistence of non-
553 communicating DHCP servers on the same wire.
555 If 'giaddr' is 0x0 in the DHCPREQUEST message, the client is on
556 the same subnet as the server. The server MUST broadcast the
557 DHCPNAK message to the 0xffffffff broadcast address because the
558 client may not have a correct network address or subnet mask, and
559 the client may not be answering ARP requests.
561 If 'giaddr' is set in the DHCPREQUEST message, the client is on a
562 different subnet. The server MUST set the broadcast bit in the
563 DHCPNAK, so that the relay agent will broadcast the DHCPNAK to the
564 client, because the client may not have a correct network address
565 or subnet mask, and the client may not be answering ARP requests.
567 o DHCPREQUEST generated during RENEWING 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 will
573 be unicast, so no relay agents will be involved in its
574 transmission. Because 'giaddr' is therefore not filled in, the
575 DHCP server will trust the value in 'ciaddr', and use it when
576 replying to the client.
578 A client MAY choose to renew or extend its lease prior to T1. The
579 server may choose not to extend the lease (as a policy decision by
580 the network administrator), but should return a DHCPACK message
583 o DHCPREQUEST generated during REBINDING state:
585 'server identifier' MUST NOT be filled in, 'requested IP address'
586 option MUST NOT be filled in, 'ciaddr' MUST be filled in with
587 client's IP address. In this situation, the client is completely
588 configured, and is trying to extend its lease. This message MUST
589 be broadcast to the 0xffffffff IP broadcast address. The DHCP
590 server SHOULD check 'ciaddr' for correctness before replying to
593 The DHCPREQUEST from a REBINDING client is intended to accommodate
594 sites that have multiple DHCP servers and a mechanism for
595 maintaining consistency among leases managed by multiple servers.
596 A DHCP server MAY extend a client's lease only if it has local
597 administrative authority to do so.
599 if (!requested_ip_opt
) {
600 requested_nip
= packet
.ciaddr
;
601 if (requested_nip
== 0) {
602 log1("no requested IP and no ciaddr, ignoring");
606 if (lease
&& requested_nip
== lease
->lease_nip
) {
607 /* client requested or configured IP matches the lease.
608 * ACK it, and bump lease expiration time. */
609 send_ACK(&packet
, lease
->lease_nip
);
612 /* No lease for this MAC, or lease IP != requested IP */
614 if (server_id_opt
/* client is in SELECTING state */
615 || requested_ip_opt
/* client is in INIT-REBOOT state */
617 /* "No, we don't have this IP for you" */
619 } /* else: client is in RENEWING or REBINDING, do not answer */
625 * "If the server receives a DHCPDECLINE message,
626 * the client has discovered through some other means
627 * that the suggested network address is already
628 * in use. The server MUST mark the network address
629 * as not available and SHOULD notify the local
630 * sysadmin of a possible configuration problem."
632 * SERVER_ID must be present,
633 * REQUESTED_IP must be present,
634 * chaddr must be filled in,
635 * ciaddr must be 0 (we do not check this)
637 log1("Received DECLINE");
640 && lease
/* chaddr matches this lease */
641 && requested_nip
== lease
->lease_nip
643 memset(lease
->lease_mac
, 0, sizeof(lease
->lease_mac
));
644 lease
->expires
= time(NULL
) + server_config
.decline_time
;
649 /* "Upon receipt of a DHCPRELEASE message, the server
650 * marks the network address as not allocated."
652 * SERVER_ID must be present,
653 * REQUESTED_IP must not be present (we do not check this),
654 * chaddr must be filled in,
655 * ciaddr must be filled in
657 log1("Received RELEASE");
659 && lease
/* chaddr matches this lease */
660 && packet
.ciaddr
== lease
->lease_nip
662 lease
->expires
= time(NULL
);
667 log1("Received INFORM");
668 send_inform(&packet
);
675 /*if (server_config.pidfile) - server_config.pidfile is never NULL */
676 remove_pidfile(server_config
.pidfile
);