1 | /* vi: set sw=4 ts=4: */
|
---|
2 | /*
|
---|
3 | * udhcp server
|
---|
4 | * Copyright (C) 1999 Matthew Ramsay <matthewr@moreton.com.au>
|
---|
5 | * Chris Trew <ctrew@moreton.com.au>
|
---|
6 | *
|
---|
7 | * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
|
---|
8 | *
|
---|
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.
|
---|
13 | *
|
---|
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.
|
---|
18 | *
|
---|
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.
|
---|
22 | */
|
---|
23 |
|
---|
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)"
|
---|
34 | //usage: )
|
---|
35 |
|
---|
36 | #include <syslog.h>
|
---|
37 | #include "common.h"
|
---|
38 | #include "dhcpc.h"
|
---|
39 | #include "dhcpd.h"
|
---|
40 |
|
---|
41 |
|
---|
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)
|
---|
44 | {
|
---|
45 | const uint8_t *chaddr;
|
---|
46 | uint32_t ciaddr;
|
---|
47 |
|
---|
48 | // Was:
|
---|
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,
|
---|
58 | // and can be used.
|
---|
59 |
|
---|
60 | if (force_broadcast
|
---|
61 | || (dhcp_pkt->flags & htons(BROADCAST_FLAG))
|
---|
62 | || dhcp_pkt->ciaddr == 0
|
---|
63 | ) {
|
---|
64 | log1("broadcasting packet to client");
|
---|
65 | ciaddr = INADDR_BROADCAST;
|
---|
66 | chaddr = MAC_BCAST_ADDR;
|
---|
67 | } else {
|
---|
68 | log1("unicasting packet to client ciaddr");
|
---|
69 | ciaddr = dhcp_pkt->ciaddr;
|
---|
70 | chaddr = dhcp_pkt->chaddr;
|
---|
71 | }
|
---|
72 |
|
---|
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);
|
---|
77 | }
|
---|
78 |
|
---|
79 | /* Send a packet to gateway_nip using the kernel ip stack */
|
---|
80 | static void send_packet_to_relay(struct dhcp_packet *dhcp_pkt)
|
---|
81 | {
|
---|
82 | log1("forwarding packet to relay");
|
---|
83 |
|
---|
84 | udhcp_send_kernel_packet(dhcp_pkt,
|
---|
85 | server_config.server_nip, SERVER_PORT,
|
---|
86 | dhcp_pkt->gateway_nip, SERVER_PORT);
|
---|
87 | }
|
---|
88 |
|
---|
89 | static void send_packet(struct dhcp_packet *dhcp_pkt, int force_broadcast)
|
---|
90 | {
|
---|
91 | if (dhcp_pkt->gateway_nip)
|
---|
92 | send_packet_to_relay(dhcp_pkt);
|
---|
93 | else
|
---|
94 | send_packet_to_client(dhcp_pkt, force_broadcast);
|
---|
95 | }
|
---|
96 |
|
---|
97 | static void init_packet(struct dhcp_packet *packet, struct dhcp_packet *oldpacket, char type)
|
---|
98 | {
|
---|
99 | /* Sets op, htype, hlen, cookie fields
|
---|
100 | * and adds DHCP_MESSAGE_TYPE option */
|
---|
101 | udhcp_init_header(packet, type);
|
---|
102 |
|
---|
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);
|
---|
109 | }
|
---|
110 |
|
---|
111 | /* Fill options field, siaddr_nip, and sname and boot_file fields.
|
---|
112 | * TODO: teach this code to use overload option.
|
---|
113 | */
|
---|
114 | static void add_server_options(struct dhcp_packet *packet)
|
---|
115 | {
|
---|
116 | struct option_set *curr = server_config.options;
|
---|
117 |
|
---|
118 | while (curr) {
|
---|
119 | if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
|
---|
120 | udhcp_add_binary_option(packet, curr->data);
|
---|
121 | curr = curr->next;
|
---|
122 | }
|
---|
123 |
|
---|
124 | packet->siaddr_nip = server_config.siaddr_nip;
|
---|
125 |
|
---|
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);
|
---|
130 | }
|
---|
131 |
|
---|
132 | static uint32_t select_lease_time(struct dhcp_packet *packet)
|
---|
133 | {
|
---|
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;
|
---|
143 | }
|
---|
144 | return lease_time_sec;
|
---|
145 | }
|
---|
146 |
|
---|
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,
|
---|
153 | unsigned arpping_ms)
|
---|
154 | {
|
---|
155 | struct dhcp_packet packet;
|
---|
156 | uint32_t lease_time_sec;
|
---|
157 | struct in_addr addr;
|
---|
158 |
|
---|
159 | init_packet(&packet, oldpacket, DHCPOFFER);
|
---|
160 |
|
---|
161 | /* If it is a static lease, use its IP */
|
---|
162 | packet.yiaddr = static_lease_nip;
|
---|
163 | /* Else: */
|
---|
164 | if (!static_lease_nip) {
|
---|
165 | /* We have no static lease for client's chaddr */
|
---|
166 | uint32_t req_nip;
|
---|
167 | const char *p_host_name;
|
---|
168 |
|
---|
169 | if (lease) {
|
---|
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.
|
---|
173 | */
|
---|
174 | packet.yiaddr = lease->lease_nip;
|
---|
175 | }
|
---|
176 | /* Or: if client has requested an IP */
|
---|
177 | else if (requested_ip_opt != NULL
|
---|
178 | /* (read IP) */
|
---|
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
|
---|
183 | /* and */
|
---|
184 | && ( !(lease = find_lease_by_nip(req_nip)) /* is not already taken */
|
---|
185 | || is_expired_lease(lease) /* or is taken, but expired */
|
---|
186 | )
|
---|
187 | ) {
|
---|
188 | packet.yiaddr = req_nip;
|
---|
189 | }
|
---|
190 | else {
|
---|
191 | /* Otherwise, find a free IP */
|
---|
192 | packet.yiaddr = find_free_or_expired_nip(oldpacket->chaddr, arpping_ms);
|
---|
193 | }
|
---|
194 |
|
---|
195 | if (!packet.yiaddr) {
|
---|
196 | bb_error_msg("no free IP addresses. OFFER abandoned");
|
---|
197 | return;
|
---|
198 | }
|
---|
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,
|
---|
203 | p_host_name,
|
---|
204 | p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
|
---|
205 | );
|
---|
206 | if (!lease) {
|
---|
207 | bb_error_msg("no free IP addresses. OFFER abandoned");
|
---|
208 | return;
|
---|
209 | }
|
---|
210 | }
|
---|
211 |
|
---|
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);
|
---|
215 |
|
---|
216 | addr.s_addr = packet.yiaddr;
|
---|
217 | bb_error_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);
|
---|
220 | }
|
---|
221 |
|
---|
222 | /* NOINLINE: limit stack usage in caller */
|
---|
223 | static NOINLINE void send_NAK(struct dhcp_packet *oldpacket)
|
---|
224 | {
|
---|
225 | struct dhcp_packet packet;
|
---|
226 |
|
---|
227 | init_packet(&packet, oldpacket, DHCPNAK);
|
---|
228 |
|
---|
229 | log1("sending %s", "NAK");
|
---|
230 | send_packet(&packet, /*force_bcast:*/ 1);
|
---|
231 | }
|
---|
232 |
|
---|
233 | /* NOINLINE: limit stack usage in caller */
|
---|
234 | static NOINLINE void send_ACK(struct dhcp_packet *oldpacket, uint32_t yiaddr)
|
---|
235 | {
|
---|
236 | struct dhcp_packet packet;
|
---|
237 | uint32_t lease_time_sec;
|
---|
238 | struct in_addr addr;
|
---|
239 | const char *p_host_name;
|
---|
240 |
|
---|
241 | init_packet(&packet, oldpacket, DHCPACK);
|
---|
242 | packet.yiaddr = yiaddr;
|
---|
243 |
|
---|
244 | lease_time_sec = select_lease_time(oldpacket);
|
---|
245 | udhcp_add_simple_option(&packet, DHCP_LEASE_TIME, htonl(lease_time_sec));
|
---|
246 |
|
---|
247 | add_server_options(&packet);
|
---|
248 |
|
---|
249 | addr.s_addr = yiaddr;
|
---|
250 | bb_error_msg("sending ACK to %s", inet_ntoa(addr));
|
---|
251 | send_packet(&packet, /*force_bcast:*/ 0);
|
---|
252 |
|
---|
253 | p_host_name = (const char*) udhcp_get_option(oldpacket, DHCP_HOST_NAME);
|
---|
254 | add_lease(packet.chaddr, packet.yiaddr,
|
---|
255 | lease_time_sec,
|
---|
256 | p_host_name,
|
---|
257 | p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
|
---|
258 | );
|
---|
259 | if (ENABLE_FEATURE_UDHCPD_WRITE_LEASES_EARLY) {
|
---|
260 | /* rewrite the file with leases at every new acceptance */
|
---|
261 | write_leases();
|
---|
262 | }
|
---|
263 | }
|
---|
264 |
|
---|
265 | /* NOINLINE: limit stack usage in caller */
|
---|
266 | static NOINLINE void send_inform(struct dhcp_packet *oldpacket)
|
---|
267 | {
|
---|
268 | struct dhcp_packet packet;
|
---|
269 |
|
---|
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.
|
---|
279 | * ...
|
---|
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'."
|
---|
284 | */
|
---|
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);
|
---|
289 |
|
---|
290 | send_packet(&packet, /*force_bcast:*/ 0);
|
---|
291 | }
|
---|
292 |
|
---|
293 |
|
---|
294 | /* globals */
|
---|
295 | struct dyn_lease *g_leases;
|
---|
296 | /* struct server_config_t server_config is in bb_common_bufsiz1 */
|
---|
297 |
|
---|
298 |
|
---|
299 | int udhcpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
|
---|
300 | int udhcpd_main(int argc UNUSED_PARAM, char **argv)
|
---|
301 | {
|
---|
302 | int server_socket = -1, retval, max_sock;
|
---|
303 | uint8_t *state;
|
---|
304 | unsigned timeout_end;
|
---|
305 | unsigned num_ips;
|
---|
306 | unsigned opt;
|
---|
307 | struct option_set *option;
|
---|
308 | char *str_I = str_I;
|
---|
309 | const char *str_a = "2000";
|
---|
310 | unsigned arpping_ms;
|
---|
311 | IF_FEATURE_UDHCP_PORT(char *str_P;)
|
---|
312 |
|
---|
313 | setup_common_bufsiz();
|
---|
314 |
|
---|
315 | IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
|
---|
316 | IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
|
---|
317 |
|
---|
318 | #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
|
---|
319 | opt_complementary = "vv";
|
---|
320 | #endif
|
---|
321 | opt = getopt32(argv, "fSI:va:"
|
---|
322 | IF_FEATURE_UDHCP_PORT("P:")
|
---|
323 | , &str_I
|
---|
324 | , &str_a
|
---|
325 | IF_FEATURE_UDHCP_PORT(, &str_P)
|
---|
326 | IF_UDHCP_VERBOSE(, &dhcp_verbose)
|
---|
327 | );
|
---|
328 | if (!(opt & 1)) { /* no -f */
|
---|
329 | bb_daemonize_or_rexec(0, argv);
|
---|
330 | logmode = LOGMODE_NONE;
|
---|
331 | }
|
---|
332 | /* update argv after the possible vfork+exec in daemonize */
|
---|
333 | argv += optind;
|
---|
334 | if (opt & 2) { /* -S */
|
---|
335 | openlog(applet_name, LOG_PID, LOG_DAEMON);
|
---|
336 | logmode |= LOGMODE_SYSLOG;
|
---|
337 | }
|
---|
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;
|
---|
341 | free(lsa);
|
---|
342 | }
|
---|
343 | #if ENABLE_FEATURE_UDHCP_PORT
|
---|
344 | if (opt & 32) { /* -P */
|
---|
345 | SERVER_PORT = xatou16(str_P);
|
---|
346 | CLIENT_PORT = SERVER_PORT + 1;
|
---|
347 | }
|
---|
348 | #endif
|
---|
349 | arpping_ms = xatou(str_a);
|
---|
350 |
|
---|
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);
|
---|
354 |
|
---|
355 | /* Make sure fd 0,1,2 are open */
|
---|
356 | bb_sanitize_stdio();
|
---|
357 | /* Equivalent of doing a fflush after every \n */
|
---|
358 | setlinebuf(stdout);
|
---|
359 |
|
---|
360 | /* Create pidfile */
|
---|
361 | write_pidfile(server_config.pidfile);
|
---|
362 | /* if (!..) bb_perror_msg("can't create pidfile %s", pidfile); */
|
---|
363 |
|
---|
364 | bb_error_msg("started, v"BB_VER);
|
---|
365 |
|
---|
366 | option = udhcp_find_option(server_config.options, DHCP_LEASE_TIME);
|
---|
367 | server_config.max_lease_sec = DEFAULT_LEASE_TIME;
|
---|
368 | if (option) {
|
---|
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);
|
---|
371 | }
|
---|
372 |
|
---|
373 | /* Sanity check */
|
---|
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;
|
---|
379 | }
|
---|
380 |
|
---|
381 | g_leases = xzalloc(server_config.max_leases * sizeof(g_leases[0]));
|
---|
382 | read_leases(server_config.lease_file);
|
---|
383 |
|
---|
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)
|
---|
388 | ) {
|
---|
389 | retval = 1;
|
---|
390 | goto ret;
|
---|
391 | }
|
---|
392 |
|
---|
393 | /* Setup the signal pipe */
|
---|
394 | udhcp_sp_setup();
|
---|
395 |
|
---|
396 | continue_with_autotime:
|
---|
397 | timeout_end = monotonic_sec() + server_config.auto_time;
|
---|
398 | while (1) { /* loop until universe collapses */
|
---|
399 | fd_set rfds;
|
---|
400 | struct dhcp_packet packet;
|
---|
401 | int bytes;
|
---|
402 | struct timeval tv;
|
---|
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;
|
---|
408 |
|
---|
409 | if (server_socket < 0) {
|
---|
410 | server_socket = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT,
|
---|
411 | server_config.interface);
|
---|
412 | }
|
---|
413 |
|
---|
414 | max_sock = udhcp_sp_fd_set(&rfds, server_socket);
|
---|
415 | if (server_config.auto_time) {
|
---|
416 | /* cast to signed is essential if tv_sec is wider than int */
|
---|
417 | tv.tv_sec = (int)(timeout_end - monotonic_sec());
|
---|
418 | tv.tv_usec = 0;
|
---|
419 | }
|
---|
420 | retval = 0;
|
---|
421 | if (!server_config.auto_time || tv.tv_sec > 0) {
|
---|
422 | retval = select(max_sock + 1, &rfds, NULL, NULL,
|
---|
423 | server_config.auto_time ? &tv : NULL);
|
---|
424 | }
|
---|
425 | if (retval == 0) {
|
---|
426 | write_leases();
|
---|
427 | goto continue_with_autotime;
|
---|
428 | }
|
---|
429 | if (retval < 0 && errno != EINTR) {
|
---|
430 | log1("error on select");
|
---|
431 | continue;
|
---|
432 | }
|
---|
433 |
|
---|
434 | switch (udhcp_sp_read(&rfds)) {
|
---|
435 | case SIGUSR1:
|
---|
436 | bb_error_msg("received %s", "SIGUSR1");
|
---|
437 | write_leases();
|
---|
438 | /* why not just reset the timeout, eh */
|
---|
439 | goto continue_with_autotime;
|
---|
440 | case SIGTERM:
|
---|
441 | bb_error_msg("received %s", "SIGTERM");
|
---|
442 | write_leases();
|
---|
443 | goto ret0;
|
---|
444 | case 0: /* no signal: read a packet */
|
---|
445 | break;
|
---|
446 | default: /* signal or error (probably EINTR): back to select */
|
---|
447 | continue;
|
---|
448 | }
|
---|
449 |
|
---|
450 | bytes = udhcp_recv_kernel_packet(&packet, server_socket);
|
---|
451 | if (bytes < 0) {
|
---|
452 | /* bytes can also be -2 ("bad packet data") */
|
---|
453 | if (bytes == -1 && errno != EINTR) {
|
---|
454 | log1("read error: %s, reopening socket", strerror(errno));
|
---|
455 | close(server_socket);
|
---|
456 | server_socket = -1;
|
---|
457 | }
|
---|
458 | continue;
|
---|
459 | }
|
---|
460 | if (packet.hlen != 6) {
|
---|
461 | bb_error_msg("MAC length != 6, ignoring packet");
|
---|
462 | continue;
|
---|
463 | }
|
---|
464 | if (packet.op != BOOTREQUEST) {
|
---|
465 | bb_error_msg("not a REQUEST, ignoring packet");
|
---|
466 | continue;
|
---|
467 | }
|
---|
468 | state = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
|
---|
469 | if (state == NULL || state[0] < DHCP_MINTYPE || state[0] > DHCP_MAXTYPE) {
|
---|
470 | bb_error_msg("no or bad message type option, ignoring packet");
|
---|
471 | continue;
|
---|
472 | }
|
---|
473 |
|
---|
474 | /* Get SERVER_ID if present */
|
---|
475 | server_id_opt = udhcp_get_option(&packet, DHCP_SERVER_ID);
|
---|
476 | if (server_id_opt) {
|
---|
477 | uint32_t server_id_network_order;
|
---|
478 | move_from_unaligned32(server_id_network_order, server_id_opt);
|
---|
479 | if (server_id_network_order != server_config.server_nip) {
|
---|
480 | /* client talks to somebody else */
|
---|
481 | log1("server ID doesn't match, ignoring");
|
---|
482 | continue;
|
---|
483 | }
|
---|
484 | }
|
---|
485 |
|
---|
486 | /* Look for a static/dynamic lease */
|
---|
487 | static_lease_nip = get_static_nip_by_mac(server_config.static_leases, &packet.chaddr);
|
---|
488 | if (static_lease_nip) {
|
---|
489 | bb_error_msg("found static lease: %x", static_lease_nip);
|
---|
490 | memcpy(&fake_lease.lease_mac, &packet.chaddr, 6);
|
---|
491 | fake_lease.lease_nip = static_lease_nip;
|
---|
492 | fake_lease.expires = 0;
|
---|
493 | lease = &fake_lease;
|
---|
494 | } else {
|
---|
495 | lease = find_lease_by_mac(packet.chaddr);
|
---|
496 | }
|
---|
497 |
|
---|
498 | /* Get REQUESTED_IP if present */
|
---|
499 | requested_ip_opt = udhcp_get_option(&packet, DHCP_REQUESTED_IP);
|
---|
500 | if (requested_ip_opt) {
|
---|
501 | move_from_unaligned32(requested_nip, requested_ip_opt);
|
---|
502 | }
|
---|
503 |
|
---|
504 | switch (state[0]) {
|
---|
505 |
|
---|
506 | case DHCPDISCOVER:
|
---|
507 | log1("received %s", "DISCOVER");
|
---|
508 |
|
---|
509 | send_offer(&packet, static_lease_nip, lease, requested_ip_opt, arpping_ms);
|
---|
510 | break;
|
---|
511 |
|
---|
512 | case DHCPREQUEST:
|
---|
513 | log1("received %s", "REQUEST");
|
---|
514 | /* RFC 2131:
|
---|
515 |
|
---|
516 | o DHCPREQUEST generated during SELECTING state:
|
---|
517 |
|
---|
518 | Client inserts the address of the selected server in 'server
|
---|
519 | identifier', 'ciaddr' MUST be zero, 'requested IP address' MUST be
|
---|
520 | filled in with the yiaddr value from the chosen DHCPOFFER.
|
---|
521 |
|
---|
522 | Note that the client may choose to collect several DHCPOFFER
|
---|
523 | messages and select the "best" offer. The client indicates its
|
---|
524 | selection by identifying the offering server in the DHCPREQUEST
|
---|
525 | message. If the client receives no acceptable offers, the client
|
---|
526 | may choose to try another DHCPDISCOVER message. Therefore, the
|
---|
527 | servers may not receive a specific DHCPREQUEST from which they can
|
---|
528 | decide whether or not the client has accepted the offer.
|
---|
529 |
|
---|
530 | o DHCPREQUEST generated during INIT-REBOOT state:
|
---|
531 |
|
---|
532 | 'server identifier' MUST NOT be filled in, 'requested IP address'
|
---|
533 | option MUST be filled in with client's notion of its previously
|
---|
534 | assigned address. 'ciaddr' MUST be zero. The client is seeking to
|
---|
535 | verify a previously allocated, cached configuration. Server SHOULD
|
---|
536 | send a DHCPNAK message to the client if the 'requested IP address'
|
---|
537 | is incorrect, or is on the wrong network.
|
---|
538 |
|
---|
539 | Determining whether a client in the INIT-REBOOT state is on the
|
---|
540 | correct network is done by examining the contents of 'giaddr', the
|
---|
541 | 'requested IP address' option, and a database lookup. If the DHCP
|
---|
542 | server detects that the client is on the wrong net (i.e., the
|
---|
543 | result of applying the local subnet mask or remote subnet mask (if
|
---|
544 | 'giaddr' is not zero) to 'requested IP address' option value
|
---|
545 | doesn't match reality), then the server SHOULD send a DHCPNAK
|
---|
546 | message to the client.
|
---|
547 |
|
---|
548 | If the network is correct, then the DHCP server should check if
|
---|
549 | the client's notion of its IP address is correct. If not, then the
|
---|
550 | server SHOULD send a DHCPNAK message to the client. If the DHCP
|
---|
551 | server has no record of this client, then it MUST remain silent,
|
---|
552 | and MAY output a warning to the network administrator. This
|
---|
553 | behavior is necessary for peaceful coexistence of non-
|
---|
554 | communicating DHCP servers on the same wire.
|
---|
555 |
|
---|
556 | If 'giaddr' is 0x0 in the DHCPREQUEST message, the client is on
|
---|
557 | the same subnet as the server. The server MUST broadcast the
|
---|
558 | DHCPNAK message to the 0xffffffff broadcast address because the
|
---|
559 | client may not have a correct network address or subnet mask, and
|
---|
560 | the client may not be answering ARP requests.
|
---|
561 |
|
---|
562 | If 'giaddr' is set in the DHCPREQUEST message, the client is on a
|
---|
563 | different subnet. The server MUST set the broadcast bit in the
|
---|
564 | DHCPNAK, so that the relay agent will broadcast the DHCPNAK to the
|
---|
565 | client, because the client may not have a correct network address
|
---|
566 | or subnet mask, and the client may not be answering ARP requests.
|
---|
567 |
|
---|
568 | o DHCPREQUEST generated during RENEWING state:
|
---|
569 |
|
---|
570 | 'server identifier' MUST NOT be filled in, 'requested IP address'
|
---|
571 | option MUST NOT be filled in, 'ciaddr' MUST be filled in with
|
---|
572 | client's IP address. In this situation, the client is completely
|
---|
573 | configured, and is trying to extend its lease. This message will
|
---|
574 | be unicast, so no relay agents will be involved in its
|
---|
575 | transmission. Because 'giaddr' is therefore not filled in, the
|
---|
576 | DHCP server will trust the value in 'ciaddr', and use it when
|
---|
577 | replying to the client.
|
---|
578 |
|
---|
579 | A client MAY choose to renew or extend its lease prior to T1. The
|
---|
580 | server may choose not to extend the lease (as a policy decision by
|
---|
581 | the network administrator), but should return a DHCPACK message
|
---|
582 | regardless.
|
---|
583 |
|
---|
584 | o DHCPREQUEST generated during REBINDING state:
|
---|
585 |
|
---|
586 | 'server identifier' MUST NOT be filled in, 'requested IP address'
|
---|
587 | option MUST NOT be filled in, 'ciaddr' MUST be filled in with
|
---|
588 | client's IP address. In this situation, the client is completely
|
---|
589 | configured, and is trying to extend its lease. This message MUST
|
---|
590 | be broadcast to the 0xffffffff IP broadcast address. The DHCP
|
---|
591 | server SHOULD check 'ciaddr' for correctness before replying to
|
---|
592 | the DHCPREQUEST.
|
---|
593 |
|
---|
594 | The DHCPREQUEST from a REBINDING client is intended to accommodate
|
---|
595 | sites that have multiple DHCP servers and a mechanism for
|
---|
596 | maintaining consistency among leases managed by multiple servers.
|
---|
597 | A DHCP server MAY extend a client's lease only if it has local
|
---|
598 | administrative authority to do so.
|
---|
599 | */
|
---|
600 | if (!requested_ip_opt) {
|
---|
601 | requested_nip = packet.ciaddr;
|
---|
602 | if (requested_nip == 0) {
|
---|
603 | log1("no requested IP and no ciaddr, ignoring");
|
---|
604 | break;
|
---|
605 | }
|
---|
606 | }
|
---|
607 | if (lease && requested_nip == lease->lease_nip) {
|
---|
608 | /* client requested or configured IP matches the lease.
|
---|
609 | * ACK it, and bump lease expiration time. */
|
---|
610 | send_ACK(&packet, lease->lease_nip);
|
---|
611 | break;
|
---|
612 | }
|
---|
613 | /* No lease for this MAC, or lease IP != requested IP */
|
---|
614 |
|
---|
615 | if (server_id_opt /* client is in SELECTING state */
|
---|
616 | || requested_ip_opt /* client is in INIT-REBOOT state */
|
---|
617 | ) {
|
---|
618 | /* "No, we don't have this IP for you" */
|
---|
619 | send_NAK(&packet);
|
---|
620 | } /* else: client is in RENEWING or REBINDING, do not answer */
|
---|
621 |
|
---|
622 | break;
|
---|
623 |
|
---|
624 | case DHCPDECLINE:
|
---|
625 | /* RFC 2131:
|
---|
626 | * "If the server receives a DHCPDECLINE message,
|
---|
627 | * the client has discovered through some other means
|
---|
628 | * that the suggested network address is already
|
---|
629 | * in use. The server MUST mark the network address
|
---|
630 | * as not available and SHOULD notify the local
|
---|
631 | * sysadmin of a possible configuration problem."
|
---|
632 | *
|
---|
633 | * SERVER_ID must be present,
|
---|
634 | * REQUESTED_IP must be present,
|
---|
635 | * chaddr must be filled in,
|
---|
636 | * ciaddr must be 0 (we do not check this)
|
---|
637 | */
|
---|
638 | log1("received %s", "DECLINE");
|
---|
639 | if (server_id_opt
|
---|
640 | && requested_ip_opt
|
---|
641 | && lease /* chaddr matches this lease */
|
---|
642 | && requested_nip == lease->lease_nip
|
---|
643 | ) {
|
---|
644 | memset(lease->lease_mac, 0, sizeof(lease->lease_mac));
|
---|
645 | lease->expires = time(NULL) + server_config.decline_time;
|
---|
646 | }
|
---|
647 | break;
|
---|
648 |
|
---|
649 | case DHCPRELEASE:
|
---|
650 | /* "Upon receipt of a DHCPRELEASE message, the server
|
---|
651 | * marks the network address as not allocated."
|
---|
652 | *
|
---|
653 | * SERVER_ID must be present,
|
---|
654 | * REQUESTED_IP must not be present (we do not check this),
|
---|
655 | * chaddr must be filled in,
|
---|
656 | * ciaddr must be filled in
|
---|
657 | */
|
---|
658 | log1("received %s", "RELEASE");
|
---|
659 | if (server_id_opt
|
---|
660 | && lease /* chaddr matches this lease */
|
---|
661 | && packet.ciaddr == lease->lease_nip
|
---|
662 | ) {
|
---|
663 | lease->expires = time(NULL);
|
---|
664 | }
|
---|
665 | break;
|
---|
666 |
|
---|
667 | case DHCPINFORM:
|
---|
668 | log1("received %s", "INFORM");
|
---|
669 | send_inform(&packet);
|
---|
670 | break;
|
---|
671 | }
|
---|
672 | }
|
---|
673 | ret0:
|
---|
674 | retval = 0;
|
---|
675 | ret:
|
---|
676 | /*if (server_config.pidfile) - server_config.pidfile is never NULL */
|
---|
677 | remove_pidfile(server_config.pidfile);
|
---|
678 | return retval;
|
---|
679 | }
|
---|