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[project/odhcpd.git] / src / dhcpv4.c
1 /**
2 * Copyright (C) 2012-2013 Steven Barth <steven@midlink.org>
3 * Copyright (C) 2016 Hans Dedecker <dedeckeh@gmail.com>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License v2 as published by
7 * the Free Software Foundation.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 *
15 */
16
17 #include <time.h>
18 #include <errno.h>
19 #include <fcntl.h>
20 #include <unistd.h>
21 #include <stddef.h>
22 #include <stdlib.h>
23 #include <resolv.h>
24 #include <limits.h>
25 #include <net/if.h>
26 #include <net/if_arp.h>
27 #include <netinet/ip.h>
28 #include <sys/ioctl.h>
29 #include <sys/timerfd.h>
30 #include <arpa/inet.h>
31
32 #include <libubox/md5.h>
33
34 #include "odhcpd.h"
35 #include "dhcpv4.h"
36 #include "dhcpv6.h"
37
38 #define PACKET_SIZE(start, end) (((uint8_t *)end - (uint8_t *)start) < DHCPV4_MIN_PACKET_SIZE ? \
39 DHCPV4_MIN_PACKET_SIZE : (uint8_t *)end - (uint8_t *)start)
40
41 static void dhcpv4_netevent_cb(unsigned long event, struct netevent_handler_info *info);
42 static int setup_dhcpv4_addresses(struct interface *iface);
43 static bool addr_is_fr_ip(struct interface *iface, struct in_addr *addr);
44 static void valid_until_cb(struct uloop_timeout *event);
45 static void handle_addrlist_change(struct interface *iface);
46 static void dhcpv4_fr_start(struct dhcp_assignment *a);
47 static void dhcpv4_fr_rand_delay(struct dhcp_assignment *a);
48 static void dhcpv4_fr_stop(struct dhcp_assignment *a);
49 static void handle_dhcpv4(void *addr, void *data, size_t len,
50 struct interface *iface, void *dest_addr);
51 static struct dhcp_assignment* dhcpv4_lease(struct interface *iface,
52 enum dhcpv4_msg msg, const uint8_t *mac, const uint32_t reqaddr,
53 uint32_t *leasetime, const char *hostname, const size_t hostname_len,
54 const bool accept_fr_nonce, bool *incl_fr_opt, uint32_t *fr_serverid,
55 const char *reqopts, const size_t reqopts_len);
56
57 static struct netevent_handler dhcpv4_netevent_handler = { .cb = dhcpv4_netevent_cb, };
58 static struct uloop_timeout valid_until_timeout = {.cb = valid_until_cb};
59 static uint32_t serial = 0;
60
61 struct odhcpd_ref_ip {
62 struct list_head head;
63 int ref_cnt;
64 struct odhcpd_ipaddr addr;
65 };
66
67 /* Create socket and register events */
68 int dhcpv4_init(void)
69 {
70 uloop_timeout_set(&valid_until_timeout, 1000);
71 netlink_add_netevent_handler(&dhcpv4_netevent_handler);
72
73 return 0;
74 }
75
76 int dhcpv4_setup_interface(struct interface *iface, bool enable)
77 {
78 int ret = 0;
79
80 enable = enable && (iface->dhcpv4 != MODE_DISABLED);
81
82 if (iface->dhcpv4_event.uloop.fd >= 0) {
83 uloop_fd_delete(&iface->dhcpv4_event.uloop);
84 close(iface->dhcpv4_event.uloop.fd);
85 iface->dhcpv4_event.uloop.fd = -1;
86 }
87
88 if (enable) {
89 struct sockaddr_in bind_addr = {AF_INET, htons(DHCPV4_SERVER_PORT),
90 {INADDR_ANY}, {0}};
91 int val = 1;
92
93 iface->dhcpv4_event.uloop.fd = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
94 if (iface->dhcpv4_event.uloop.fd < 0) {
95 syslog(LOG_ERR, "socket(AF_INET): %m");
96 ret = -1;
97 goto out;
98 }
99
100 /* Basic IPv4 configuration */
101 if (setsockopt(iface->dhcpv4_event.uloop.fd, SOL_SOCKET, SO_REUSEADDR,
102 &val, sizeof(val)) < 0) {
103 syslog(LOG_ERR, "setsockopt(SO_REUSEADDR): %m");
104 ret = -1;
105 goto out;
106 }
107
108 if (setsockopt(iface->dhcpv4_event.uloop.fd, SOL_SOCKET, SO_BROADCAST,
109 &val, sizeof(val)) < 0) {
110 syslog(LOG_ERR, "setsockopt(SO_BROADCAST): %m");
111 ret = -1;
112 goto out;
113 }
114
115 if (setsockopt(iface->dhcpv4_event.uloop.fd, IPPROTO_IP, IP_PKTINFO,
116 &val, sizeof(val)) < 0) {
117 syslog(LOG_ERR, "setsockopt(IP_PKTINFO): %m");
118 ret = -1;
119 goto out;
120 }
121
122 val = IPTOS_PREC_INTERNETCONTROL;
123 if (setsockopt(iface->dhcpv4_event.uloop.fd, IPPROTO_IP, IP_TOS,
124 &val, sizeof(val)) < 0) {
125 syslog(LOG_ERR, "setsockopt(IP_TOS): %m");
126 ret = -1;
127 goto out;
128 }
129
130 val = IP_PMTUDISC_DONT;
131 if (setsockopt(iface->dhcpv4_event.uloop.fd, IPPROTO_IP, IP_MTU_DISCOVER,
132 &val, sizeof(val)) < 0) {
133 syslog(LOG_ERR, "setsockopt(IP_MTU_DISCOVER): %m");
134 ret = -1;
135 goto out;
136 }
137
138 if (setsockopt(iface->dhcpv4_event.uloop.fd, SOL_SOCKET, SO_BINDTODEVICE,
139 iface->ifname, strlen(iface->ifname)) < 0) {
140 syslog(LOG_ERR, "setsockopt(SO_BINDTODEVICE): %m");
141 ret = -1;
142 goto out;
143 }
144
145 if (bind(iface->dhcpv4_event.uloop.fd, (struct sockaddr*)&bind_addr,
146 sizeof(bind_addr)) < 0) {
147 syslog(LOG_ERR, "bind(): %m");
148 ret = -1;
149 goto out;
150 }
151
152 if (setup_dhcpv4_addresses(iface) < 0) {
153 ret = -1;
154 goto out;
155 }
156
157 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
158 odhcpd_register(&iface->dhcpv4_event);
159 } else {
160 while (!list_empty(&iface->dhcpv4_assignments))
161 free_assignment(list_first_entry(&iface->dhcpv4_assignments,
162 struct dhcp_assignment, head));
163 }
164
165 out:
166 if (ret < 0 && iface->dhcpv4_event.uloop.fd >= 0) {
167 close(iface->dhcpv4_event.uloop.fd);
168 iface->dhcpv4_event.uloop.fd = -1;
169 }
170
171 return ret;
172 }
173
174
175 static void dhcpv4_netevent_cb(unsigned long event, struct netevent_handler_info *info)
176 {
177 struct interface *iface = info->iface;
178
179 if (!iface || iface->dhcpv4 == MODE_DISABLED)
180 return;
181
182 switch (event) {
183 case NETEV_IFINDEX_CHANGE:
184 dhcpv4_setup_interface(iface, true);
185 break;
186 case NETEV_ADDRLIST_CHANGE:
187 handle_addrlist_change(iface);
188 break;
189 default:
190 break;
191 }
192 }
193
194 static struct dhcp_assignment *find_assignment_by_hwaddr(struct interface *iface, const uint8_t *hwaddr)
195 {
196 struct dhcp_assignment *a;
197
198 list_for_each_entry(a, &iface->dhcpv4_assignments, head)
199 if (!memcmp(a->hwaddr, hwaddr, 6))
200 return a;
201
202 return NULL;
203 }
204
205 static int setup_dhcpv4_addresses(struct interface *iface)
206 {
207 iface->dhcpv4_start_ip.s_addr = INADDR_ANY;
208 iface->dhcpv4_end_ip.s_addr = INADDR_ANY;
209 iface->dhcpv4_local.s_addr = INADDR_ANY;
210 iface->dhcpv4_bcast.s_addr = INADDR_ANY;
211 iface->dhcpv4_mask.s_addr = INADDR_ANY;
212
213 /* Sanity checks */
214 if (iface->dhcpv4_start.s_addr & htonl(0xffff0000) ||
215 iface->dhcpv4_end.s_addr & htonl(0xffff0000) ||
216 ntohl(iface->dhcpv4_start.s_addr) > ntohl(iface->dhcpv4_end.s_addr)) {
217 syslog(LOG_WARNING, "Invalid DHCP range for %s", iface->name);
218 return -1;
219 }
220
221 if (!iface->addr4_len) {
222 syslog(LOG_WARNING, "No network(s) available on %s", iface->name);
223 return -1;
224 }
225
226 uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
227 uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
228
229 for (size_t i = 0; i < iface->addr4_len && start && end; i++) {
230 struct in_addr *addr = &iface->addr4[i].addr.in;
231 struct in_addr mask;
232
233 if (addr_is_fr_ip(iface, addr))
234 continue;
235
236 odhcpd_bitlen2netmask(false, iface->addr4[i].prefix, &mask);
237 if ((start & ntohl(~mask.s_addr)) == start &&
238 (end & ntohl(~mask.s_addr)) == end &&
239 end < ntohl(~mask.s_addr)) { /* Exclude broadcast address */
240 iface->dhcpv4_start_ip.s_addr = htonl(start) |
241 (addr->s_addr & mask.s_addr);
242 iface->dhcpv4_end_ip.s_addr = htonl(end) |
243 (addr->s_addr & mask.s_addr);
244 iface->dhcpv4_local = *addr;
245 iface->dhcpv4_bcast = iface->addr4[i].broadcast;
246 iface->dhcpv4_mask = mask;
247 return 0;
248 }
249 }
250
251 /* Don't allocate IP range for subnets bigger than 28 */
252 if (iface->addr4[0].prefix > 28) {
253 syslog(LOG_WARNING, "Auto allocation of DHCP range fails on %s", iface->name);
254 return -1;
255 }
256
257 iface->dhcpv4_local = iface->addr4[0].addr.in;
258 iface->dhcpv4_bcast = iface->addr4[0].broadcast;
259 odhcpd_bitlen2netmask(false, iface->addr4[0].prefix, &iface->dhcpv4_mask);
260 end = start = iface->dhcpv4_local.s_addr & iface->dhcpv4_mask.s_addr;
261
262 /* Auto allocate ranges */
263 if (ntohl(iface->dhcpv4_mask.s_addr) <= 0xffffff00) { /* /24, 150 of 256, [100..249] */
264 iface->dhcpv4_start_ip.s_addr = start | htonl(100);
265 iface->dhcpv4_end_ip.s_addr = end | htonl(100 + 150 - 1);
266 } else if (ntohl(iface->dhcpv4_mask.s_addr) <= 0xffffff80) { /* /25, 100 of 128, [20..119] */
267 iface->dhcpv4_start_ip.s_addr = start | htonl(20);
268 iface->dhcpv4_end_ip.s_addr = end | htonl(20 + 100 - 1);
269 } else if (ntohl(iface->dhcpv4_mask.s_addr) <= 0xffffffc0) { /* /26, 50 of 64, [10..59] */
270 iface->dhcpv4_start_ip.s_addr = start | htonl(10);
271 iface->dhcpv4_end_ip.s_addr = end | htonl(10 + 50 - 1);
272 } else if (ntohl(iface->dhcpv4_mask.s_addr) <= 0xffffffe0) { /* /27, 20 of 32, [10..29] */
273 iface->dhcpv4_start_ip.s_addr = start | htonl(10);
274 iface->dhcpv4_end_ip.s_addr = end | htonl(10 + 20 - 1);
275 } else { /* /28, 10 of 16, [3..12] */
276 iface->dhcpv4_start_ip.s_addr = start | htonl(3);
277 iface->dhcpv4_end_ip.s_addr = end | htonl(3 + 10 - 1);
278 }
279
280 return 0;
281 }
282
283 static void inc_ref_cnt_ip(struct odhcpd_ref_ip **ptr, struct odhcpd_ref_ip *ip)
284 {
285 *ptr = ip;
286 ip->ref_cnt++;
287 }
288
289 static void decr_ref_cnt_ip(struct odhcpd_ref_ip **ptr, struct interface *iface)
290 {
291 struct odhcpd_ref_ip *ip = *ptr;
292
293 if (--ip->ref_cnt == 0) {
294 netlink_setup_addr(&ip->addr, iface->ifindex, false, false);
295
296 list_del(&ip->head);
297 free(ip);
298 }
299
300 *ptr = NULL;
301 }
302
303 static bool addr_is_fr_ip(struct interface *iface, struct in_addr *addr)
304 {
305 struct odhcpd_ref_ip *p;
306
307 list_for_each_entry(p, &iface->dhcpv4_fr_ips, head) {
308 if (addr->s_addr == p->addr.addr.in.s_addr)
309 return true;
310 }
311
312 return false;
313 }
314
315 static bool leases_require_fr(struct interface *iface, struct odhcpd_ipaddr *addr,
316 uint32_t mask)
317 {
318 struct dhcp_assignment *a = NULL;
319 struct odhcpd_ref_ip *fr_ip = NULL;
320
321 list_for_each_entry(a, &iface->dhcpv4_assignments, head) {
322 if ((a->accept_fr_nonce || iface->dhcpv4_forcereconf) &&
323 !a->fr_ip &&
324 ((a->addr & mask) == (addr->addr.in.s_addr & mask))) {
325 if (!fr_ip) {
326 fr_ip = calloc(1, sizeof(*fr_ip));
327 if (!fr_ip)
328 break;
329
330 list_add(&fr_ip->head, &iface->dhcpv4_fr_ips);
331 fr_ip->addr = *addr;
332 }
333 inc_ref_cnt_ip(&a->fr_ip, fr_ip);
334 }
335 }
336
337 return fr_ip ? true : false;
338 }
339
340 static void valid_until_cb(struct uloop_timeout *event)
341 {
342 struct interface *iface;
343 time_t now = odhcpd_time();
344
345 avl_for_each_element(&interfaces, iface, avl) {
346 struct dhcp_assignment *a, *n;
347
348 if (iface->dhcpv4 != MODE_SERVER)
349 continue;
350
351 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
352 if (!INFINITE_VALID(a->valid_until) && a->valid_until < now)
353 free_assignment(a);
354 }
355 }
356 uloop_timeout_set(event, 1000);
357 }
358
359 static void handle_addrlist_change(struct interface *iface)
360 {
361 struct odhcpd_ipaddr ip;
362 struct odhcpd_ref_ip *a;
363 struct dhcp_assignment *c;
364 uint32_t mask = iface->dhcpv4_mask.s_addr;
365
366 memset(&ip, 0, sizeof(ip));
367 ip.addr.in = iface->dhcpv4_local;
368 ip.prefix = odhcpd_netmask2bitlen(false, &iface->dhcpv4_mask);
369 ip.broadcast = iface->dhcpv4_bcast;
370
371 setup_dhcpv4_addresses(iface);
372
373 if ((ip.addr.in.s_addr & mask) ==
374 (iface->dhcpv4_local.s_addr & iface->dhcpv4_mask.s_addr))
375 return;
376
377 if (ip.addr.in.s_addr && !leases_require_fr(iface, &ip, mask))
378 return;
379
380 if (iface->dhcpv4_local.s_addr == INADDR_ANY || list_empty(&iface->dhcpv4_fr_ips))
381 return;
382
383 a = list_first_entry(&iface->dhcpv4_fr_ips, struct odhcpd_ref_ip, head);
384
385 if (netlink_setup_addr(&a->addr, iface->ifindex, false, true)) {
386 syslog(LOG_WARNING, "Failed to add ip address on %s", iface->name);
387 return;
388 }
389
390 list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
391 if ((c->flags & OAF_BOUND) && c->fr_ip && !c->fr_cnt) {
392 if (c->accept_fr_nonce || iface->dhcpv4_forcereconf)
393 dhcpv4_fr_rand_delay(c);
394 else
395 dhcpv4_fr_stop(c);
396 }
397 }
398 }
399
400 static char *dhcpv4_msg_to_string(uint8_t reqmsg)
401 {
402 switch (reqmsg) {
403 case (DHCPV4_MSG_DISCOVER):
404 return "DHCPV4_MSG_DISCOVER";
405 case (DHCPV4_MSG_OFFER):
406 return "DHCPV4_MSG_OFFER";
407 case (DHCPV4_MSG_REQUEST):
408 return "DHCPV4_MSG_REQUEST";
409 case (DHCPV4_MSG_DECLINE):
410 return "DHCPV4_MSG_DECLINE";
411 case (DHCPV4_MSG_ACK):
412 return "DHCPV4_MSG_ACK";
413 case (DHCPV4_MSG_NAK):
414 return "DHCPV4_MSG_NAK";
415 case (DHCPV4_MSG_RELEASE):
416 return "DHCPV4_MSG_RELEASE";
417 case (DHCPV4_MSG_INFORM):
418 return "DHCPV4_MSG_INFORM";
419 case (DHCPV4_MSG_FORCERENEW):
420 return "DHCPV4_MSG_FORCERENEW";
421 default:
422 return "UNKNOWN";
423 }
424 }
425
426 static void dhcpv4_free_assignment(struct dhcp_assignment *a)
427 {
428 if (a->fr_ip)
429 dhcpv4_fr_stop(a);
430 }
431
432 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
433 uint8_t type, uint8_t len, const void *data)
434 {
435 uint8_t *c = *cookie;
436 uint8_t *end = (uint8_t *)msg + sizeof(*msg);
437 bool tag_only = type == DHCPV4_OPT_PAD || type == DHCPV4_OPT_END;
438 int total_len = tag_only ? 1 : 2 + len;
439
440 if (*cookie + total_len > end)
441 return;
442
443 *cookie += total_len;
444 *c++ = type;
445
446 if (tag_only)
447 return;
448
449 *c++ = len;
450 memcpy(c, data, len);
451 }
452
453 static void dhcpv4_fr_send(struct dhcp_assignment *a)
454 {
455 struct dhcpv4_message fr_msg = {
456 .op = DHCPV4_BOOTREPLY,
457 .htype = 1,
458 .hlen = 6,
459 .hops = 0,
460 .secs = 0,
461 .flags = 0,
462 .ciaddr = {INADDR_ANY},
463 .yiaddr = {INADDR_ANY},
464 .siaddr = {INADDR_ANY},
465 .giaddr = {INADDR_ANY},
466 .chaddr = {0},
467 .sname = {0},
468 .file = {0},
469 };
470 struct dhcpv4_auth_forcerenew *auth_o, auth = {
471 .protocol = 3,
472 .algorithm = 1,
473 .rdm = 0,
474 .replay = {htonl(time(NULL)), htonl(++serial)},
475 .type = 2,
476 .key = {0},
477 };
478 struct interface *iface = a->iface;
479
480 odhcpd_urandom(&fr_msg.xid, sizeof(fr_msg.xid));
481 memcpy(fr_msg.chaddr, a->hwaddr, fr_msg.hlen);
482
483 fr_msg.options[0] = 0x63;
484 fr_msg.options[1] = 0x82;
485 fr_msg.options[2] = 0x53;
486 fr_msg.options[3] = 0x63;
487
488 uint8_t *cookie = &fr_msg.options[4];
489 uint8_t msg = DHCPV4_MSG_FORCERENEW;
490
491 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
492 if (a->accept_fr_nonce) {
493 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_AUTHENTICATION, sizeof(auth), &auth);
494 auth_o = (struct dhcpv4_auth_forcerenew *)(cookie - sizeof(auth));
495 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_END, 0, NULL);
496
497 md5_ctx_t md5;
498 uint8_t secretbytes[64];
499 memset(secretbytes, 0, sizeof(secretbytes));
500 memcpy(secretbytes, a->key, sizeof(a->key));
501
502 for (size_t i = 0; i < sizeof(secretbytes); ++i)
503 secretbytes[i] ^= 0x36;
504
505 md5_begin(&md5);
506 md5_hash(secretbytes, sizeof(secretbytes), &md5);
507 md5_hash(&fr_msg, sizeof(fr_msg), &md5);
508 md5_end(auth_o->key, &md5);
509
510 for (size_t i = 0; i < sizeof(secretbytes); ++i) {
511 secretbytes[i] ^= 0x36;
512 secretbytes[i] ^= 0x5c;
513 }
514
515 md5_begin(&md5);
516 md5_hash(secretbytes, sizeof(secretbytes), &md5);
517 md5_hash(auth_o->key, sizeof(auth_o->key), &md5);
518 md5_end(auth_o->key, &md5);
519 } else {
520 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_SERVERID, 4,
521 &a->fr_ip->addr.addr.in.s_addr);
522 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_END, 0, NULL);
523 }
524
525 struct sockaddr_in dest;
526 memset(&dest, 0, sizeof(dest));
527 dest.sin_family = AF_INET;
528 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
529 dest.sin_addr.s_addr = a->addr;
530
531 if (sendto(iface->dhcpv4_event.uloop.fd, &fr_msg, PACKET_SIZE(&fr_msg, cookie),
532 MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest)) < 0)
533 syslog(LOG_ERR, "Failed to send %s to %s - %s: %m", dhcpv4_msg_to_string(msg),
534 odhcpd_print_mac(a->hwaddr, sizeof(a->hwaddr)), inet_ntoa(dest.sin_addr));
535 else
536 syslog(LOG_DEBUG, "Sent %s to %s - %s", dhcpv4_msg_to_string(msg),
537 odhcpd_print_mac(a->hwaddr, sizeof(a->hwaddr)), inet_ntoa(dest.sin_addr));
538 }
539
540 static void dhcpv4_fr_timer(struct uloop_timeout *event)
541 {
542 struct dhcp_assignment *a = container_of(event, struct dhcp_assignment, fr_timer);
543
544 if (a->fr_cnt > 0 && a->fr_cnt < 8) {
545 dhcpv4_fr_send(a);
546 uloop_timeout_set(&a->fr_timer, 1000 << a->fr_cnt);
547 a->fr_cnt++;
548 } else
549 dhcpv4_fr_stop(a);
550 }
551
552 static void dhcpv4_fr_start(struct dhcp_assignment *a)
553 {
554 uloop_timeout_set(&a->fr_timer, 1000 << a->fr_cnt);
555 a->fr_timer.cb = dhcpv4_fr_timer;
556 a->fr_cnt++;
557
558 dhcpv4_fr_send(a);
559 }
560
561 static void dhcpv4_fr_delay_timer(struct uloop_timeout *event)
562 {
563 struct dhcp_assignment *a = container_of(event, struct dhcp_assignment, fr_timer);
564 struct interface *iface = a->iface;
565
566 (iface->dhcpv4_event.uloop.fd == -1 ? dhcpv4_fr_rand_delay(a) : dhcpv4_fr_start(a));
567 }
568
569 static void dhcpv4_fr_rand_delay(struct dhcp_assignment *a)
570 {
571 #define MIN_DELAY 500
572 #define MAX_FUZZ 500
573 int msecs;
574
575 odhcpd_urandom(&msecs, sizeof(msecs));
576
577 msecs = labs(msecs)%MAX_FUZZ + MIN_DELAY;
578
579 uloop_timeout_set(&a->fr_timer, msecs);
580 a->fr_timer.cb = dhcpv4_fr_delay_timer;
581 }
582
583 static void dhcpv4_fr_stop(struct dhcp_assignment *a)
584 {
585 uloop_timeout_cancel(&a->fr_timer);
586 decr_ref_cnt_ip(&a->fr_ip, a->iface);
587 a->fr_cnt = 0;
588 a->fr_timer.cb = NULL;
589 }
590
591 static int dhcpv4_send_reply(const void *buf, size_t len,
592 const struct sockaddr *dest, socklen_t dest_len,
593 void *opaque)
594 {
595 int *sock = opaque;
596
597 return sendto(*sock, buf, len, MSG_DONTWAIT, dest, dest_len);
598 }
599
600 /* Handler for DHCPv4 messages */
601 static void handle_dhcpv4(void *addr, void *data, size_t len,
602 struct interface *iface, _unused void *dest_addr)
603 {
604 int sock = iface->dhcpv4_event.uloop.fd;
605
606 dhcpv4_handle_msg(addr, data, len, iface, dest_addr, dhcpv4_send_reply, &sock);
607 }
608
609 void dhcpv4_handle_msg(void *addr, void *data, size_t len,
610 struct interface *iface, _unused void *dest_addr,
611 send_reply_cb_t send_reply, void *opaque)
612 {
613 struct dhcpv4_message *req = data;
614
615 if (iface->dhcpv4 == MODE_DISABLED)
616 return;
617
618 if (len < offsetof(struct dhcpv4_message, options) + 4 ||
619 req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
620 return;
621
622 syslog(LOG_DEBUG, "Got DHCPv4 request on %s", iface->name);
623
624 if (!iface->dhcpv4_start_ip.s_addr && !iface->dhcpv4_end_ip.s_addr) {
625 syslog(LOG_WARNING, "No DHCP range available on %s", iface->name);
626 return;
627 }
628
629 int sock = iface->dhcpv4_event.uloop.fd;
630
631 struct dhcpv4_message reply = {
632 .op = DHCPV4_BOOTREPLY,
633 .htype = req->htype,
634 .hlen = req->hlen,
635 .hops = 0,
636 .xid = req->xid,
637 .secs = 0,
638 .flags = req->flags,
639 .ciaddr = {INADDR_ANY},
640 .giaddr = req->giaddr,
641 .siaddr = iface->dhcpv4_local,
642 };
643 memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
644
645 reply.options[0] = 0x63;
646 reply.options[1] = 0x82;
647 reply.options[2] = 0x53;
648 reply.options[3] = 0x63;
649
650 uint8_t *cookie = &reply.options[4];
651 uint8_t reqmsg = DHCPV4_MSG_REQUEST;
652 uint8_t msg = DHCPV4_MSG_ACK;
653
654 uint32_t reqaddr = INADDR_ANY;
655 uint32_t leasetime = 0;
656 size_t hostname_len = 0;
657 size_t reqopts_len = 0;
658 char hostname[256];
659 char reqopts[256];
660 bool accept_fr_nonce = false;
661 bool incl_fr_opt = false;
662
663 uint8_t *start = &req->options[4];
664 uint8_t *end = ((uint8_t*)data) + len;
665 struct dhcpv4_option *opt;
666 dhcpv4_for_each_option(start, end, opt) {
667 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1)
668 reqmsg = opt->data[0];
669 else if (opt->type == DHCPV4_OPT_REQOPTS && opt->len > 0) {
670 reqopts_len = opt->len;
671 memcpy(reqopts, opt->data, reqopts_len);
672 reqopts[reqopts_len] = 0;
673 } else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
674 hostname_len = opt->len;
675 memcpy(hostname, opt->data, hostname_len);
676 hostname[hostname_len] = 0;
677 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4)
678 memcpy(&reqaddr, opt->data, 4);
679 else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
680 if (memcmp(opt->data, &iface->dhcpv4_local, 4))
681 return;
682 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
683 uint8_t *c = opt->data, *cend = &opt->data[opt->len];
684 for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
685 size_t elen = strlen(iface->filter_class);
686 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
687 return; // Ignore from homenet
688 }
689 } else if (opt->type == DHCPV4_OPT_LEASETIME && opt->len == 4)
690 memcpy(&leasetime, opt->data, 4);
691 else if (opt->type == DHCPV4_OPT_FORCERENEW_NONCE_CAPABLE && opt->len > 0) {
692 for (uint8_t i = 0; i < opt->len; i++) {
693 if (opt->data[i] == 1) {
694 accept_fr_nonce = true;
695 break;
696 }
697 }
698
699 }
700 }
701
702 if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
703 reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
704 reqmsg != DHCPV4_MSG_RELEASE)
705 return;
706
707 struct dhcp_assignment *a = NULL;
708 uint32_t serverid = iface->dhcpv4_local.s_addr;
709 uint32_t fr_serverid = INADDR_ANY;
710
711 if (reqmsg != DHCPV4_MSG_INFORM)
712 a = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr,
713 &leasetime, hostname, hostname_len,
714 accept_fr_nonce, &incl_fr_opt, &fr_serverid,
715 reqopts, reqopts_len);
716
717 if (!a) {
718 if (reqmsg == DHCPV4_MSG_REQUEST)
719 msg = DHCPV4_MSG_NAK;
720 else if (reqmsg == DHCPV4_MSG_DISCOVER)
721 return;
722 } else if (reqmsg == DHCPV4_MSG_DISCOVER)
723 msg = DHCPV4_MSG_OFFER;
724 else if (reqmsg == DHCPV4_MSG_REQUEST &&
725 ((reqaddr && reqaddr != a->addr) ||
726 (req->ciaddr.s_addr && req->ciaddr.s_addr != a->addr))) {
727 msg = DHCPV4_MSG_NAK;
728 /*
729 * DHCP client requested an IP which we can't offer to him. Probably the
730 * client changed the network or the network has been changed. The reply
731 * type is set to DHCPV4_MSG_NAK, because the client should not use that IP.
732 *
733 * For modern devices we build an answer that includes a valid IP, like
734 * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
735 * perform additional DHCP round trips.
736 *
737 */
738
739 /*
740 *
741 * Buggy clients do serverid checking in nack messages; therefore set the
742 * serverid in nack messages triggered by a previous force renew equal to
743 * the server id in use at that time by the server
744 *
745 */
746 if (fr_serverid)
747 serverid = fr_serverid;
748
749 if (req->ciaddr.s_addr &&
750 ((iface->dhcpv4_start_ip.s_addr & iface->dhcpv4_mask.s_addr) !=
751 (req->ciaddr.s_addr & iface->dhcpv4_mask.s_addr)))
752 req->ciaddr.s_addr = INADDR_ANY;
753 }
754
755 syslog(LOG_INFO, "Received %s from %s on %s", dhcpv4_msg_to_string(reqmsg),
756 odhcpd_print_mac(req->chaddr, req->hlen), iface->name);
757
758 #ifdef WITH_UBUS
759 if (reqmsg == DHCPV4_MSG_RELEASE)
760 ubus_bcast_dhcp_event("dhcp.release", req->chaddr, req->hlen,
761 &req->ciaddr, a ? a->hostname : NULL, iface->ifname);
762 #endif
763 if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
764 return;
765
766 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
767 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &serverid);
768
769 if (a) {
770 uint32_t val;
771
772 reply.yiaddr.s_addr = a->addr;
773
774 val = htonl(leasetime);
775 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
776
777 if (leasetime != UINT32_MAX) {
778 val = htonl(500 * leasetime / 1000);
779 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
780
781 val = htonl(875 * leasetime / 1000);
782 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
783 }
784
785 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4,
786 &iface->dhcpv4_mask.s_addr);
787
788 if (a->hostname)
789 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
790 strlen(a->hostname), a->hostname);
791
792 if (iface->dhcpv4_bcast.s_addr != INADDR_ANY)
793 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &iface->dhcpv4_bcast);
794
795 if (incl_fr_opt) {
796 if (reqmsg == DHCPV4_MSG_REQUEST) {
797 struct dhcpv4_auth_forcerenew auth = {
798 .protocol = 3,
799 .algorithm = 1,
800 .rdm = 0,
801 .replay = {htonl(time(NULL)), htonl(++serial)},
802 .type = 1,
803 .key = {0},
804 };
805
806 memcpy(auth.key, a->key, sizeof(auth.key));
807 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_AUTHENTICATION, sizeof(auth), &auth);
808 } else {
809 uint8_t one = 1;
810 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_FORCERENEW_NONCE_CAPABLE,
811 sizeof(one), &one);
812 }
813 }
814 }
815
816 struct ifreq ifr;
817
818 memset(&ifr, 0, sizeof(ifr));
819 strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name) - 1);
820
821 if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
822 uint16_t mtu = htons(ifr.ifr_mtu);
823 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
824 }
825
826 if (iface->search && iface->search_len <= 255)
827 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
828 iface->search_len, iface->search);
829 else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
830 uint8_t search_buf[256];
831 int len = dn_comp(_res.dnsrch[0], search_buf,
832 sizeof(search_buf), NULL, NULL);
833 if (len > 0)
834 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
835 len, search_buf);
836 }
837
838 if (iface->dhcpv4_router_cnt == 0)
839 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &iface->dhcpv4_local);
840 else
841 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
842 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
843
844
845 if (iface->dhcpv4_dns_cnt == 0) {
846 if (iface->dns_service)
847 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &iface->dhcpv4_local);
848 } else
849 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
850 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
851
852
853 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
854
855 struct sockaddr_in dest = *((struct sockaddr_in*)addr);
856 if (req->giaddr.s_addr) {
857 /*
858 * relay agent is configured, send reply to the agent
859 */
860 dest.sin_addr = req->giaddr;
861 dest.sin_port = htons(DHCPV4_SERVER_PORT);
862 } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
863 /*
864 * client has existing configuration (ciaddr is set) AND this address is
865 * not the address it used for the dhcp message
866 */
867 dest.sin_addr = req->ciaddr;
868 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
869 } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
870 req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
871 /*
872 * client requests a broadcast reply OR we can't offer an IP
873 */
874 dest.sin_addr.s_addr = INADDR_BROADCAST;
875 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
876 } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
877 /*
878 * client has no previous configuration -> no IP, so we need to reply
879 * with a broadcast packet
880 */
881 dest.sin_addr.s_addr = INADDR_BROADCAST;
882 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
883 } else {
884 struct arpreq arp = {.arp_flags = ATF_COM};
885
886 /*
887 * send reply to the newly (in this proccess) allocated IP
888 */
889 dest.sin_addr = reply.yiaddr;
890 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
891
892 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
893 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
894 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
895
896 if (ioctl(sock, SIOCSARP, &arp) < 0)
897 syslog(LOG_ERR, "ioctl(SIOCSARP): %m");
898 }
899
900 if (send_reply(&reply, PACKET_SIZE(&reply, cookie),
901 (struct sockaddr*)&dest, sizeof(dest), opaque) < 0)
902 syslog(LOG_ERR, "Failed to send %s to %s - %s: %m",
903 dhcpv4_msg_to_string(msg),
904 dest.sin_addr.s_addr == INADDR_BROADCAST ?
905 "ff:ff:ff:ff:ff:ff": odhcpd_print_mac(req->chaddr, req->hlen),
906 inet_ntoa(dest.sin_addr));
907 else
908 syslog(LOG_DEBUG, "Sent %s to %s - %s",
909 dhcpv4_msg_to_string(msg),
910 dest.sin_addr.s_addr == INADDR_BROADCAST ?
911 "ff:ff:ff:ff:ff:ff": odhcpd_print_mac(req->chaddr, req->hlen),
912 inet_ntoa(dest.sin_addr));
913
914
915 #ifdef WITH_UBUS
916 if (msg == DHCPV4_MSG_ACK)
917 ubus_bcast_dhcp_event("dhcp.ack", req->chaddr, req->hlen, &reply.yiaddr,
918 a ? a->hostname : NULL, iface->ifname);
919 #endif
920 }
921
922 static bool dhcpv4_insert_assignment(struct list_head *list, struct dhcp_assignment *a,
923 uint32_t addr)
924 {
925 uint32_t h_addr = ntohl(addr);
926 struct dhcp_assignment *c;
927
928 list_for_each_entry(c, list, head) {
929 uint32_t c_addr = ntohl(c->addr);
930
931 if (c_addr == h_addr)
932 return false;
933
934 if (c_addr > h_addr)
935 break;
936 }
937
938 /* Insert new node before c (might match list head) */
939 a->addr = addr;
940 list_add_tail(&a->head, &c->head);
941
942 return true;
943 }
944
945 static char* ip4toa(uint32_t addr)
946 {
947 static char buf[16];
948
949 snprintf(buf, sizeof(buf), "%u.%u.%u.%u",
950 ((uint8_t *)&addr)[0], ((uint8_t *)&addr)[1],
951 ((uint8_t *)&addr)[2], ((uint8_t *)&addr)[3]);
952
953 return buf;
954 }
955
956 static bool dhcpv4_assign(struct interface *iface, struct dhcp_assignment *a,
957 uint32_t raddr)
958 {
959 uint32_t start = ntohl(iface->dhcpv4_start_ip.s_addr);
960 uint32_t end = ntohl(iface->dhcpv4_end_ip.s_addr);
961 uint32_t count = end - start + 1;
962 uint32_t seed = 0;
963 bool assigned;
964
965 /* Preconfigured IP address by static lease */
966 if (a->addr) {
967 assigned = dhcpv4_insert_assignment(&iface->dhcpv4_assignments,
968 a, a->addr);
969
970 if (assigned)
971 syslog(LOG_DEBUG, "Assigning static IP: %s", ip4toa(a->addr));
972
973 return assigned;
974 }
975
976 /* try to assign the IP the client asked for */
977 if (start <= ntohl(raddr) && ntohl(raddr) <= end &&
978 !config_find_lease_by_ipaddr(raddr)) {
979 assigned = dhcpv4_insert_assignment(&iface->dhcpv4_assignments,
980 a, raddr);
981
982 if (assigned) {
983 syslog(LOG_DEBUG, "Assigning the IP the client asked for: %s",
984 ip4toa(a->addr));
985
986 return true;
987 }
988 }
989
990 /* Seed RNG with checksum of hwaddress */
991 for (size_t i = 0; i < sizeof(a->hwaddr); ++i) {
992 /* Knuth's multiplicative method */
993 uint8_t o = a->hwaddr[i];
994 seed += (o*2654435761) % UINT32_MAX;
995 }
996
997 srand(seed);
998
999 for (uint32_t i = 0, try = (((uint32_t)rand()) % count) + start; i < count;
1000 ++i, try = (((try - start) + 1) % count) + start) {
1001 uint32_t n_try = htonl(try);
1002
1003 if (config_find_lease_by_ipaddr(n_try))
1004 continue;
1005
1006 assigned = dhcpv4_insert_assignment(&iface->dhcpv4_assignments,
1007 a, n_try);
1008
1009 if (assigned) {
1010 syslog(LOG_DEBUG, "Assigning mapped IP: %s (try %u of %u)",
1011 ip4toa(a->addr), i + 1, count);
1012
1013 return true;
1014 }
1015 }
1016
1017 syslog(LOG_NOTICE, "Can't assign any IP address -> address space is full");
1018
1019 return false;
1020 }
1021
1022
1023 static struct dhcp_assignment*
1024 dhcpv4_lease(struct interface *iface, enum dhcpv4_msg msg, const uint8_t *mac,
1025 const uint32_t reqaddr, uint32_t *leasetime, const char *hostname,
1026 const size_t hostname_len, const bool accept_fr_nonce, bool *incl_fr_opt,
1027 uint32_t *fr_serverid, const char* reqopts, const size_t reqopts_len)
1028 {
1029 struct dhcp_assignment *a = find_assignment_by_hwaddr(iface, mac);
1030 struct lease *l = config_find_lease_by_mac(mac);
1031 time_t now = odhcpd_time();
1032
1033 if (l && a && a->lease != l) {
1034 free_assignment(a);
1035 a = NULL;
1036 }
1037
1038 if (a && (a->flags & OAF_BOUND) && a->fr_ip) {
1039 *fr_serverid = a->fr_ip->addr.addr.in.s_addr;
1040 dhcpv4_fr_stop(a);
1041 }
1042
1043 if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
1044 bool assigned = !!a;
1045
1046 if (!a) {
1047 if (!iface->no_dynamic_dhcp || l) {
1048 /* Create new binding */
1049 a = alloc_assignment(0);
1050 if (!a) {
1051 syslog(LOG_WARNING, "Failed to alloc assignment on interface %s",
1052 iface->ifname);
1053 return NULL;
1054 }
1055 memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
1056 /* Set valid time to 0 for static lease indicating */
1057 /* infinite lifetime otherwise current time */
1058 a->valid_until = l ? 0 : now;
1059 a->dhcp_free_cb = dhcpv4_free_assignment;
1060 a->iface = iface;
1061 a->flags = OAF_DHCPV4;
1062 a->addr = l ? l->ipaddr : INADDR_ANY;
1063
1064 assigned = dhcpv4_assign(iface, a, reqaddr);
1065
1066 if (l) {
1067 a->flags |= OAF_STATIC;
1068
1069 if (l->hostname)
1070 a->hostname = strdup(l->hostname);
1071
1072 if (l->leasetime)
1073 a->leasetime = l->leasetime;
1074
1075 list_add(&a->lease_list, &l->assignments);
1076 a->lease = l;
1077 }
1078 }
1079 } else if (((a->addr & iface->dhcpv4_mask.s_addr) !=
1080 (iface->dhcpv4_start_ip.s_addr & iface->dhcpv4_mask.s_addr)) &&
1081 !(a->flags & OAF_STATIC)) {
1082 list_del_init(&a->head);
1083 a->addr = INADDR_ANY;
1084
1085 assigned = dhcpv4_assign(iface, a, reqaddr);
1086 }
1087
1088 if (assigned) {
1089 uint32_t my_leasetime;
1090
1091 if (a->leasetime)
1092 my_leasetime = a->leasetime;
1093 else
1094 my_leasetime = iface->dhcp_leasetime;
1095
1096 if ((*leasetime == 0) || (my_leasetime < *leasetime))
1097 *leasetime = my_leasetime;
1098
1099 if (msg == DHCPV4_MSG_DISCOVER) {
1100 a->flags &= ~OAF_BOUND;
1101
1102 *incl_fr_opt = accept_fr_nonce;
1103 a->valid_until = now;
1104 } else {
1105 if ((!(a->flags & OAF_STATIC) || !a->hostname) && hostname_len > 0) {
1106 a->hostname = realloc(a->hostname, hostname_len + 1);
1107 if (a->hostname) {
1108 memcpy(a->hostname, hostname, hostname_len);
1109 a->hostname[hostname_len] = 0;
1110
1111 if (odhcpd_valid_hostname(a->hostname))
1112 a->flags &= ~OAF_BROKEN_HOSTNAME;
1113 else
1114 a->flags |= OAF_BROKEN_HOSTNAME;
1115 }
1116 }
1117
1118 if (reqopts_len > 0) {
1119 a->reqopts = realloc(a->reqopts, reqopts_len + 1);
1120 if (a->reqopts) {
1121 memcpy(a->reqopts, reqopts, reqopts_len);
1122 a->reqopts[reqopts_len] = 0;
1123 }
1124 }
1125
1126 if (!(a->flags & OAF_BOUND)) {
1127 a->accept_fr_nonce = accept_fr_nonce;
1128 *incl_fr_opt = accept_fr_nonce;
1129 odhcpd_urandom(a->key, sizeof(a->key));
1130 a->flags |= OAF_BOUND;
1131 } else
1132 *incl_fr_opt = false;
1133
1134 a->valid_until = ((*leasetime == UINT32_MAX) ? 0 : (time_t)(now + *leasetime));
1135 }
1136 } else if (!assigned && a) {
1137 /* Cleanup failed assignment */
1138 free_assignment(a);
1139 a = NULL;
1140 }
1141
1142 } else if (msg == DHCPV4_MSG_RELEASE && a) {
1143 a->flags &= ~OAF_BOUND;
1144 a->valid_until = now - 1;
1145
1146 } else if (msg == DHCPV4_MSG_DECLINE && a) {
1147 a->flags &= ~OAF_BOUND;
1148
1149 if (!(a->flags & OAF_STATIC) || a->lease->ipaddr != a->addr) {
1150 memset(a->hwaddr, 0, sizeof(a->hwaddr));
1151 a->valid_until = now + 3600; /* Block address for 1h */
1152 } else
1153 a->valid_until = now - 1;
1154 }
1155
1156 dhcpv6_ia_write_statefile();
1157
1158 return a;
1159 }
OpenWrt DHCP Server