b803359360618ccd103b2bc1c92128a4f7e5c43c
[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 static void dhcpv4_netevent_cb(unsigned long event, struct netevent_handler_info *info);
39 static int setup_dhcpv4_addresses(struct interface *iface);
40 static void update_static_assignments(struct interface *iface);
41 static void valid_until_cb(struct uloop_timeout *event);
42 static void handle_addrlist_change(struct interface *iface);
43 static void free_dhcpv4_assignment(struct dhcpv4_assignment *a);
44 static void dhcpv4_fr_start(struct dhcpv4_assignment *a);
45 static void dhcpv4_fr_stop(struct dhcpv4_assignment *a);
46 static void handle_dhcpv4(void *addr, void *data, size_t len,
47                 struct interface *iface, void *dest_addr);
48 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
49                 enum dhcpv4_msg msg, const uint8_t *mac, const uint32_t reqaddr,
50                 uint32_t *leasetime, const char *hostname, const size_t hostname_len,
51                 const bool accept_fr_nonce, bool *incl_fr_opt, uint32_t *fr_serverid);
52
53 static struct netevent_handler dhcpv4_netevent_handler = { .cb = dhcpv4_netevent_cb, };
54 static struct uloop_timeout valid_until_timeout = {.cb = valid_until_cb};
55 static uint32_t serial = 0;
56
57 struct odhcpd_ref_ip {
58         struct list_head head;
59         int ref_cnt;
60         struct odhcpd_ipaddr addr;
61 };
62
63 /* Create socket and register events */
64 int dhcpv4_init(void)
65 {
66         uloop_timeout_set(&valid_until_timeout, 1000);
67         netlink_add_netevent_handler(&dhcpv4_netevent_handler);
68
69         return 0;
70 }
71
72 int dhcpv4_setup_interface(struct interface *iface, bool enable)
73 {
74         int ret = 0;
75
76         if (iface->dhcpv4_event.uloop.fd > 0) {
77                 uloop_fd_delete(&iface->dhcpv4_event.uloop);
78                 close(iface->dhcpv4_event.uloop.fd);
79                 iface->dhcpv4_event.uloop.fd = -1;
80         }
81
82         if (iface->dhcpv4 && enable) {
83                 struct sockaddr_in bind_addr = {AF_INET, htons(DHCPV4_SERVER_PORT),
84                                         {INADDR_ANY}, {0}};
85                 int val = 1;
86
87                 if (!iface->dhcpv4_assignments.next)
88                         INIT_LIST_HEAD(&iface->dhcpv4_assignments);
89
90                 if (!iface->dhcpv4_fr_ips.next)
91                         INIT_LIST_HEAD(&iface->dhcpv4_fr_ips);
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))) {
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))) {
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))) {
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))) {
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, sizeof(bind_addr))) {
146                         syslog(LOG_ERR, "bind(): %m");
147                         ret = -1;
148                         goto out;
149                 }
150
151                 if (setup_dhcpv4_addresses(iface) < 0) {
152                         ret = -1;
153                         goto out;
154                 }
155
156                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
157                 odhcpd_register(&iface->dhcpv4_event);
158
159                 update_static_assignments(iface);
160         } else if (iface->dhcpv4_assignments.next) {
161                 while (!list_empty(&iface->dhcpv4_assignments))
162                         free_dhcpv4_assignment(list_first_entry(&iface->dhcpv4_assignments,
163                                                         struct dhcpv4_assignment, head));
164         }
165
166 out:
167         if (ret < 0 && iface->dhcpv4_event.uloop.fd > 0) {
168                 close(iface->dhcpv4_event.uloop.fd);
169                 iface->dhcpv4_event.uloop.fd = -1;
170         }
171
172         return ret;
173 }
174
175
176 static void dhcpv4_netevent_cb(unsigned long event, struct netevent_handler_info *info)
177 {
178         struct interface *iface = info->iface;
179
180         if (!iface || iface->dhcpv4 == MODE_DISABLED)
181                 return;
182
183         switch (event) {
184         case NETEV_IFINDEX_CHANGE:
185                 dhcpv4_setup_interface(iface, true);
186                 break;
187         case NETEV_ADDRLIST_CHANGE:
188                 handle_addrlist_change(iface);
189                 break;
190         default:
191                 break;
192         }
193 }
194
195 static struct dhcpv4_assignment *find_assignment_by_hwaddr(struct interface *iface, const uint8_t *hwaddr)
196 {
197         struct dhcpv4_assignment *a;
198
199         list_for_each_entry(a, &iface->dhcpv4_assignments, head)
200                 if (!memcmp(a->hwaddr, hwaddr, 6))
201                         return a;
202
203         return NULL;
204 }
205
206 static struct dhcpv4_assignment *find_assignment_by_addr(struct interface *iface, const uint32_t addr)
207 {
208         struct dhcpv4_assignment *a;
209
210         list_for_each_entry(a, &iface->dhcpv4_assignments, head)
211                 if (a->addr == addr)
212                         return a;
213
214         return NULL;
215 }
216
217 static int setup_dhcpv4_addresses(struct interface *iface)
218 {
219         iface->dhcpv4_start_ip.s_addr = INADDR_ANY;
220         iface->dhcpv4_end_ip.s_addr = INADDR_ANY;
221         iface->dhcpv4_local.s_addr = INADDR_ANY;
222         iface->dhcpv4_bcast.s_addr = INADDR_ANY;
223         iface->dhcpv4_mask.s_addr = INADDR_ANY;
224
225         /* Sanity checks */
226         if (iface->dhcpv4_start.s_addr & htonl(0xffff0000) ||
227             iface->dhcpv4_end.s_addr & htonl(0xffff0000) ||
228             ntohl(iface->dhcpv4_start.s_addr) > ntohl(iface->dhcpv4_end.s_addr)) {
229                 syslog(LOG_ERR, "invalid DHCP range for %s", iface->name);
230                 return -1;
231         }
232
233         if (!iface->addr4_len) {
234                 syslog(LOG_WARNING, "no network(s) available on %s", iface->name);
235                 return -1;
236         }
237
238         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
239         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
240
241         for (size_t i = 0; i < iface->addr4_len && start && end; i++) {
242                 struct in_addr *addr = &iface->addr4[i].addr.in;
243                 struct in_addr mask;
244
245                 odhcpd_bitlen2netmask(false, iface->addr4[i].prefix, &mask);
246                 if ((start & ntohl(~mask.s_addr)) == start &&
247                             (end & ntohl(~mask.s_addr)) == end) {
248                         iface->dhcpv4_start_ip.s_addr = htonl(start) |
249                                                         (addr->s_addr & mask.s_addr);
250                         iface->dhcpv4_end_ip.s_addr = htonl(end) |
251                                                         (addr->s_addr & mask.s_addr);
252                         iface->dhcpv4_local = *addr;
253                         iface->dhcpv4_bcast = iface->addr4[i].broadcast;
254                         iface->dhcpv4_mask = mask;
255                         return 0;
256                 }
257         }
258
259         /* Don't allocate IP range for subnets bigger than 28 */
260         if (iface->addr4[0].prefix > 28) {
261                 syslog(LOG_WARNING, "auto allocation of DHCP range fails on %s", iface->name);
262                 return -1;
263         }
264
265         iface->dhcpv4_local = iface->addr4[0].addr.in;
266         iface->dhcpv4_bcast = iface->addr4[0].broadcast;
267         odhcpd_bitlen2netmask(false, iface->addr4[0].prefix, &iface->dhcpv4_mask);
268         end = start = iface->dhcpv4_local.s_addr & iface->dhcpv4_mask.s_addr;
269
270         /* Auto allocate ranges */
271         if (ntohl(iface->dhcpv4_mask.s_addr) <= 0xffffff00) {
272                 iface->dhcpv4_start_ip.s_addr = start | htonl(100);
273                 iface->dhcpv4_end_ip.s_addr = end | htonl(250);
274         } else if (ntohl(iface->dhcpv4_mask.s_addr) <= 0xffffffc0) {
275                 iface->dhcpv4_start_ip.s_addr = start | htonl(10);
276                 iface->dhcpv4_end_ip.s_addr = end | htonl(60);
277         } else if (ntohl(iface->dhcpv4_mask.s_addr) <= 0xffffffe0) {
278                 iface->dhcpv4_start_ip.s_addr = start | htonl(10);
279                 iface->dhcpv4_end_ip.s_addr = end | htonl(30);
280         } else {
281                 iface->dhcpv4_start_ip.s_addr = start | htonl(3);
282                 iface->dhcpv4_end_ip.s_addr = end | htonl(12);
283         }
284
285         return 0;
286 }
287
288 static void update_static_assignments(struct interface *iface)
289 {
290         struct dhcpv4_assignment *a, *c;
291
292         /* Cleanup static entries not belonging to the network */
293         list_for_each_entry_safe(a, c, &iface->dhcpv4_assignments, head) {
294                 if ((a->flags & OAF_STATIC) &&
295                                 ((a->addr & iface->dhcpv4_mask.s_addr) !=
296                                  (iface->dhcpv4_start.s_addr & iface->dhcpv4_mask.s_addr)))
297                         free_dhcpv4_assignment(a);
298         }
299
300         /* Parse static entries */
301         struct lease *lease;
302         list_for_each_entry(lease, &leases, head) {
303                 if ((iface->dhcpv4_start_ip.s_addr & iface->dhcpv4_mask.s_addr) !=
304                                 (lease->ipaddr.s_addr & iface->dhcpv4_mask.s_addr)) {
305                         continue;
306                 }
307
308                 a = find_assignment_by_hwaddr(iface, lease->mac.ether_addr_octet);
309
310                 if (!a) {
311                         /* Check if there's an assignment with the specified IP address */
312                         if (find_assignment_by_addr(iface, lease->ipaddr.s_addr))
313                                 continue;
314
315                         /* Construct entry */
316                         a = calloc(1, sizeof(*a));
317                         if (!a) {
318                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
319                                         iface->ifname);
320                                 continue;
321                         }
322                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
323                 }
324
325                 a->leasetime = lease->dhcpv4_leasetime;
326
327                 a->addr = lease->ipaddr.s_addr;
328                 /* Static assignment */
329                 a->flags |= OAF_STATIC;
330                 /* Infinite valid */
331                 a->valid_until = 0;
332                 a->iface = iface;
333                 if (lease->hostname[0]) {
334                         free(a->hostname);
335                         a->hostname = strdup(lease->hostname);
336                 }
337
338                 /* Assign to all interfaces */
339                 list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
340                         if (ntohl(c->addr) > ntohl(a->addr)) {
341                                 list_add_tail(&a->head, &c->head);
342                                 break;
343                         }
344                 }
345
346                 if (&c->head == &iface->dhcpv4_assignments)
347                         list_add(&a->head, &iface->dhcpv4_assignments);
348         }
349 }
350
351 static void inc_ref_cnt_ip(struct odhcpd_ref_ip **ptr, struct odhcpd_ref_ip *ip)
352 {
353         *ptr = ip;
354         ip->ref_cnt++;
355 }
356
357 static void decr_ref_cnt_ip(struct odhcpd_ref_ip **ptr, struct interface *iface)
358 {
359         struct odhcpd_ref_ip *ip = *ptr;
360
361         if (--ip->ref_cnt == 0) {
362                 netlink_setup_addr(&ip->addr, iface->ifindex, false, false);
363
364                 list_del(&ip->head);
365                 free(ip);
366         }
367
368         *ptr = NULL;
369 }
370
371 static bool leases_require_fr(struct interface *iface, struct odhcpd_ipaddr *addr,
372                                 uint32_t mask)
373 {
374         struct dhcpv4_assignment *a = NULL;
375         struct odhcpd_ref_ip *fr_ip = NULL;
376
377         list_for_each_entry(a, &iface->dhcpv4_assignments, head) {
378                 if ((a->accept_fr_nonce || iface->dhcpv4_forcereconf) &&
379                     !a->fr_ip &&
380                     ((a->addr & mask) == (addr->addr.in.s_addr & mask))) {
381                         if (!fr_ip) {
382                                 fr_ip = calloc(1, sizeof(*fr_ip));
383                                 if (!fr_ip)
384                                         break;
385
386                                 list_add(&fr_ip->head, &iface->dhcpv4_fr_ips);
387                                 fr_ip->addr = *addr;
388                         }
389                         inc_ref_cnt_ip(&a->fr_ip, fr_ip);
390                 }
391         }
392
393         return fr_ip ? true : false;
394 }
395
396 static void valid_until_cb(struct uloop_timeout *event)
397 {
398         time_t now = odhcpd_time();
399         struct interface *iface;
400         list_for_each_entry(iface, &interfaces, head) {
401                 if (iface->dhcpv4 != MODE_SERVER || iface->dhcpv4_assignments.next == NULL)
402                         continue;
403
404                 struct dhcpv4_assignment *a, *n;
405                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
406                         if (!INFINITE_VALID(a->valid_until) && a->valid_until < now)
407                                 free_dhcpv4_assignment(a);
408                 }
409         }
410         uloop_timeout_set(event, 1000);
411 }
412
413 static void handle_addrlist_change(struct interface *iface)
414 {
415         struct odhcpd_ipaddr ip;
416         struct odhcpd_ref_ip *a;
417         struct dhcpv4_assignment *c;
418         uint32_t mask = iface->dhcpv4_mask.s_addr;
419
420         memset(&ip, 0, sizeof(ip));
421         ip.addr.in = iface->dhcpv4_local;
422         ip.prefix = odhcpd_netmask2bitlen(false, &iface->dhcpv4_mask);
423         ip.broadcast = iface->dhcpv4_bcast;
424
425         setup_dhcpv4_addresses(iface);
426
427         if ((ip.addr.in.s_addr & mask) ==
428             (iface->dhcpv4_local.s_addr & iface->dhcpv4_mask.s_addr))
429                 return;
430
431         if (ip.addr.in.s_addr && !leases_require_fr(iface, &ip, mask))
432                 return;
433
434         if (iface->dhcpv4_local.s_addr == INADDR_ANY || list_empty(&iface->dhcpv4_fr_ips))
435                 return;
436
437         a = list_first_entry(&iface->dhcpv4_fr_ips, struct odhcpd_ref_ip, head);
438
439         if (netlink_setup_addr(&a->addr, iface->ifindex, false, true)) {
440                 syslog(LOG_ERR, "Failed to add ip address");
441                 return;
442         }
443
444         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
445                 if ((c->flags & OAF_BOUND) && c->fr_ip && !c->fr_cnt) {
446                         if (c->accept_fr_nonce || iface->dhcpv4_forcereconf)
447                                 dhcpv4_fr_start(c);
448                         else
449                                 dhcpv4_fr_stop(c);
450                 }
451         }
452 }
453
454 static char *dhcpv4_msg_to_string(uint8_t reqmsg)
455 {
456         switch (reqmsg) {
457         case (DHCPV4_MSG_DISCOVER):
458                 return "DHCPV4_MSG_DISCOVER";
459         case (DHCPV4_MSG_OFFER):
460                 return "DHCPV4_MSG_OFFER";
461         case (DHCPV4_MSG_REQUEST):
462                 return "DHCPV4_MSG_REQUEST";
463         case (DHCPV4_MSG_DECLINE):
464                 return "DHCPV4_MSG_DECLINE";
465         case (DHCPV4_MSG_ACK):
466                 return "DHCPV4_MSG_ACK";
467         case (DHCPV4_MSG_NAK):
468                 return "DHCPV4_MSG_NAK";
469         case (DHCPV4_MSG_RELEASE):
470                 return "DHCPV4_MSG_RELEASE";
471         case (DHCPV4_MSG_INFORM):
472                 return "DHCPV4_MSG_INFORM";
473         case (DHCPV4_MSG_FORCERENEW):
474                 return "DHCPV4_MSG_FORCERENEW";
475         default:
476                 return "UNKNOWN";
477         }
478 }
479
480 static void free_dhcpv4_assignment(struct dhcpv4_assignment *a)
481 {
482         if (a->head.next)
483                 list_del(&a->head);
484
485         if (a->fr_ip)
486                 dhcpv4_fr_stop(a);
487
488         free(a->hostname);
489         free(a);
490 }
491
492 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
493                 uint8_t type, uint8_t len, const void *data)
494 {
495         uint8_t *c = *cookie;
496         uint8_t *end = (uint8_t *)msg + sizeof(*msg);
497
498         if (*cookie + 2 + len > end)
499                 return;
500
501         *c++ = type;
502         *c++ = len;
503         memcpy(c, data, len);
504
505         *cookie = c + len;
506 }
507
508 static void dhcpv4_fr_send(struct dhcpv4_assignment *a)
509 {
510         struct dhcpv4_message fr_msg = {
511                 .op = DHCPV4_BOOTREPLY,
512                 .htype = 1,
513                 .hlen = 6,
514                 .hops = 0,
515                 .secs = 0,
516                 .flags = 0,
517                 .ciaddr = {INADDR_ANY},
518                 .yiaddr = {INADDR_ANY},
519                 .siaddr = {INADDR_ANY},
520                 .giaddr = {INADDR_ANY},
521                 .chaddr = {0},
522                 .sname = {0},
523                 .file = {0},
524         };
525         struct dhcpv4_auth_forcerenew *auth_o, auth = {
526                 .protocol = 3,
527                 .algorithm = 1,
528                 .rdm = 0,
529                 .replay = {htonl(time(NULL)), htonl(++serial)},
530                 .type = 2,
531                 .key = {0},
532         };
533         struct interface *iface = a->iface;
534
535         odhcpd_urandom(&fr_msg.xid, sizeof(fr_msg.xid));
536         memcpy(fr_msg.chaddr, a->hwaddr, fr_msg.hlen);
537
538         fr_msg.options[0] = 0x63;
539         fr_msg.options[1] = 0x82;
540         fr_msg.options[2] = 0x53;
541         fr_msg.options[3] = 0x63;
542
543         uint8_t *cookie = &fr_msg.options[4];
544         uint8_t msg = DHCPV4_MSG_FORCERENEW;
545
546         dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
547         if (a->accept_fr_nonce) {
548                 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_AUTHENTICATION, sizeof(auth), &auth);
549                 auth_o = (struct dhcpv4_auth_forcerenew *)(cookie - sizeof(auth));
550                 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_END, 0, NULL);
551
552                 md5_ctx_t md5;
553                 uint8_t secretbytes[64];
554                 memset(secretbytes, 0, sizeof(secretbytes));
555                 memcpy(secretbytes, a->key, sizeof(a->key));
556
557                 for (size_t i = 0; i < sizeof(secretbytes); ++i)
558                         secretbytes[i] ^= 0x36;
559
560                 md5_begin(&md5);
561                 md5_hash(secretbytes, sizeof(secretbytes), &md5);
562                 md5_hash(&fr_msg, sizeof(fr_msg), &md5);
563                 md5_end(auth_o->key, &md5);
564
565                 for (size_t i = 0; i < sizeof(secretbytes); ++i) {
566                         secretbytes[i] ^= 0x36;
567                         secretbytes[i] ^= 0x5c;
568                 }
569
570                 md5_begin(&md5);
571                 md5_hash(secretbytes, sizeof(secretbytes), &md5);
572                 md5_hash(auth_o->key, sizeof(auth_o->key), &md5);
573                 md5_end(auth_o->key, &md5);
574         } else {
575                 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_SERVERID, 4,
576                                 &a->fr_ip->addr.addr.in.s_addr);
577                 dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_END, 0, NULL);
578         }
579
580         struct sockaddr_in dest;
581         memset(&dest, 0, sizeof(dest));
582         dest.sin_family = AF_INET;
583         dest.sin_port = htons(DHCPV4_CLIENT_PORT);
584         dest.sin_addr.s_addr = a->addr;
585
586         syslog(LOG_WARNING, "sending %s to %02x:%02x:%02x:%02x:%02x:%02x - %s",
587                         dhcpv4_msg_to_string(msg),
588                         a->hwaddr[0], a->hwaddr[1], a->hwaddr[2],
589                         a->hwaddr[3], a->hwaddr[4], a->hwaddr[5],
590                         inet_ntoa(dest.sin_addr));
591
592         sendto(iface->dhcpv4_event.uloop.fd, &fr_msg, sizeof(fr_msg),
593                         MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest));
594 }
595
596 static void dhcpv4_fr_timer(struct uloop_timeout *event)
597 {
598         struct dhcpv4_assignment *a = container_of(event, struct dhcpv4_assignment, fr_timer);
599
600         if (a->fr_cnt > 0 && a->fr_cnt < 8) {
601                 dhcpv4_fr_send(a);
602                 uloop_timeout_set(&a->fr_timer, 1000 << a->fr_cnt);
603                 a->fr_cnt++;
604         } else
605                 dhcpv4_fr_stop(a);
606 }
607
608 static void dhcpv4_fr_start(struct dhcpv4_assignment *a)
609 {
610         uloop_timeout_set(&a->fr_timer, 1000 << a->fr_cnt);
611         a->fr_timer.cb = dhcpv4_fr_timer;
612         a->fr_cnt++;
613
614         dhcpv4_fr_send(a);
615 }
616
617 static void dhcpv4_fr_stop(struct dhcpv4_assignment *a)
618 {
619         uloop_timeout_cancel(&a->fr_timer);
620         decr_ref_cnt_ip(&a->fr_ip, a->iface);
621         a->fr_cnt = 0;
622         a->fr_timer.cb = NULL;
623 }
624
625 // Handler for DHCPv4 messages
626 static void handle_dhcpv4(void *addr, void *data, size_t len,
627                 struct interface *iface, _unused void *dest_addr)
628 {
629         if (!iface->dhcpv4)
630                 return;
631
632         struct dhcpv4_message *req = data;
633         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
634                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
635                 return;
636
637
638         syslog(LOG_NOTICE, "Got DHCPv4 request");
639
640         if (!iface->dhcpv4_start_ip.s_addr && !iface->dhcpv4_end_ip.s_addr) {
641                 syslog(LOG_WARNING, "No DHCP range available on %s", iface->name);
642                 return;
643         }
644
645         int sock = iface->dhcpv4_event.uloop.fd;
646
647         struct dhcpv4_message reply = {
648                 .op = DHCPV4_BOOTREPLY,
649                 .htype = req->htype,
650                 .hlen = req->hlen,
651                 .hops = 0,
652                 .xid = req->xid,
653                 .secs = 0,
654                 .flags = req->flags,
655                 .ciaddr = {INADDR_ANY},
656                 .giaddr = req->giaddr,
657                 .siaddr = iface->dhcpv4_local,
658         };
659         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
660
661         reply.options[0] = 0x63;
662         reply.options[1] = 0x82;
663         reply.options[2] = 0x53;
664         reply.options[3] = 0x63;
665
666         uint8_t *cookie = &reply.options[4];
667         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
668         uint8_t msg = DHCPV4_MSG_ACK;
669
670         uint32_t reqaddr = INADDR_ANY;
671         uint32_t leasetime = 0;
672         size_t hostname_len = 0;
673         char hostname[256];
674         bool accept_fr_nonce = false;
675         bool incl_fr_opt = false;
676
677         uint8_t *start = &req->options[4];
678         uint8_t *end = ((uint8_t*)data) + len;
679         struct dhcpv4_option *opt;
680         dhcpv4_for_each_option(start, end, opt) {
681                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1)
682                         reqmsg = opt->data[0];
683                 else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
684                         hostname_len = opt->len;
685                         memcpy(hostname, opt->data, hostname_len);
686                         hostname[hostname_len] = 0;
687                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4)
688                         memcpy(&reqaddr, opt->data, 4);
689                 else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
690                         if (memcmp(opt->data, &iface->dhcpv4_local, 4))
691                                 return;
692                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
693                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
694                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
695                                 size_t elen = strlen(iface->filter_class);
696                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
697                                         return; // Ignore from homenet
698                         }
699                 } else if (opt->type == DHCPV4_OPT_LEASETIME && opt->len == 4)
700                         memcpy(&leasetime, opt->data, 4);
701                 else if (opt->type == DHCPV4_OPT_FORCERENEW_NONCE_CAPABLE && opt->len > 0) {
702                         for (uint8_t i = 0; i < opt->len; i++) {
703                                 if (opt->data[i] == 1) {
704                                         accept_fr_nonce = true;
705                                         break;
706                                 }
707                         }
708
709                 }
710         }
711
712         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
713                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
714                         reqmsg != DHCPV4_MSG_RELEASE)
715                 return;
716
717         struct dhcpv4_assignment *lease = NULL;
718         uint32_t serverid = iface->dhcpv4_local.s_addr;
719         uint32_t fr_serverid = INADDR_ANY;
720
721         if (reqmsg != DHCPV4_MSG_INFORM)
722                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr,
723                                         &leasetime, hostname, hostname_len,
724                                         accept_fr_nonce, &incl_fr_opt, &fr_serverid);
725
726         if (!lease) {
727                 if (reqmsg == DHCPV4_MSG_REQUEST)
728                         msg = DHCPV4_MSG_NAK;
729                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
730                         return;
731         } else if (reqmsg == DHCPV4_MSG_DISCOVER)
732                 msg = DHCPV4_MSG_OFFER;
733         else if (reqmsg == DHCPV4_MSG_REQUEST &&
734                         ((reqaddr && reqaddr != lease->addr) ||
735                          (req->ciaddr.s_addr && req->ciaddr.s_addr != lease->addr))) {
736                 msg = DHCPV4_MSG_NAK;
737                 /*
738                  * DHCP client requested an IP which we can't offer to him. Probably the
739                  * client changed the network or the network has been changed. The reply
740                  * type is set to DHCPV4_MSG_NAK, because the client should not use that IP.
741                  *
742                  * For modern devices we build an answer that includes a valid IP, like
743                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
744                  * perform additional DHCP round trips.
745                  *
746                  */
747
748                 /*
749                  *
750                  * Buggy clients do serverid checking in nack messages; therefore set the
751                  * serverid in nack messages triggered by a previous force renew equal to
752                  * the server id in use at that time by the server
753                  *
754                  */
755                 if (fr_serverid)
756                         serverid = fr_serverid;
757
758                 if (req->ciaddr.s_addr &&
759                                 ((iface->dhcpv4_start_ip.s_addr & iface->dhcpv4_mask.s_addr) !=
760                                  (req->ciaddr.s_addr & iface->dhcpv4_mask.s_addr)))
761                         req->ciaddr.s_addr = INADDR_ANY;
762         }
763
764         syslog(LOG_WARNING, "received %s from %02x:%02x:%02x:%02x:%02x:%02x",
765                         dhcpv4_msg_to_string(reqmsg),
766                         req->chaddr[0],req->chaddr[1],req->chaddr[2],
767                         req->chaddr[3],req->chaddr[4],req->chaddr[5]);
768
769 #ifdef WITH_UBUS
770         if (reqmsg == DHCPV4_MSG_RELEASE)
771                 ubus_bcast_dhcp_event("dhcp.release", req->chaddr, req->hlen,
772                                         &req->ciaddr, hostname, iface->ifname);
773 #endif
774         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
775                 return;
776
777         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
778         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &serverid);
779
780         if (lease) {
781                 uint32_t val;
782
783                 reply.yiaddr.s_addr = lease->addr;
784
785                 val = htonl(leasetime);
786                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
787
788                 if (leasetime != UINT32_MAX) {
789                         val = htonl(500 * leasetime / 1000);
790                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
791
792                         val = htonl(875 * leasetime / 1000);
793                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
794                 }
795
796                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4,
797                                 &iface->dhcpv4_mask.s_addr);
798
799                 if (lease->hostname)
800                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
801                                         strlen(lease->hostname), lease->hostname);
802
803                 if (iface->dhcpv4_bcast.s_addr != INADDR_ANY)
804                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &iface->dhcpv4_bcast);
805
806                 if (incl_fr_opt) {
807                         if (reqmsg == DHCPV4_MSG_REQUEST) {
808                                 struct dhcpv4_auth_forcerenew auth = {
809                                         .protocol = 3,
810                                         .algorithm = 1,
811                                         .rdm = 0,
812                                         .replay = {htonl(time(NULL)), htonl(++serial)},
813                                         .type = 1,
814                                         .key = {0},
815                                 };
816
817                                 memcpy(auth.key, lease->key, sizeof(auth.key));
818                                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_AUTHENTICATION, sizeof(auth), &auth);
819                         } else {
820                                 uint8_t one = 1;
821                                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_FORCERENEW_NONCE_CAPABLE,
822                                         sizeof(one), &one);
823                         }
824                 }
825         }
826
827         struct ifreq ifr;
828
829         memset(&ifr, 0, sizeof(ifr));
830         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name) - 1);
831
832         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
833                 uint16_t mtu = htons(ifr.ifr_mtu);
834                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
835         }
836
837         if (iface->search && iface->search_len <= 255)
838                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
839                                 iface->search_len, iface->search);
840         else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
841                 uint8_t search_buf[256];
842                 int len = dn_comp(_res.dnsrch[0], search_buf,
843                                                 sizeof(search_buf), NULL, NULL);
844                 if (len > 0)
845                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
846                                         len, search_buf);
847         }
848
849         if (iface->dhcpv4_router_cnt == 0)
850                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &iface->dhcpv4_local);
851         else
852                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
853                                 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
854
855
856         if (iface->dhcpv4_dns_cnt == 0)
857                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &iface->dhcpv4_local);
858         else
859                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
860                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
861
862
863         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
864
865         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
866         if (req->giaddr.s_addr) {
867                 /*
868                  * relay agent is configured, send reply to the agent
869                  */
870                 dest.sin_addr = req->giaddr;
871                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
872         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
873                 /*
874                  * client has existing configuration (ciaddr is set) AND this address is
875                  * not the address it used for the dhcp message
876                  */
877                 dest.sin_addr = req->ciaddr;
878                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
879         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
880                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
881                 /*
882                  * client requests a broadcast reply OR we can't offer an IP
883                  */
884                 dest.sin_addr.s_addr = INADDR_BROADCAST;
885                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
886         } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
887                 /*
888                  * client has no previous configuration -> no IP, so we need to reply
889                  * with a broadcast packet
890                  */
891                 dest.sin_addr.s_addr = INADDR_BROADCAST;
892                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
893         } else {
894                 /*
895                  * send reply to the newly (in this proccess) allocated IP
896                  */
897                 dest.sin_addr = reply.yiaddr;
898                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
899
900                 struct arpreq arp = {.arp_flags = ATF_COM};
901                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
902                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
903                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
904                 ioctl(sock, SIOCSARP, &arp);
905         }
906
907         if (dest.sin_addr.s_addr == INADDR_BROADCAST)
908                 /* reply goes to IP broadcast -> MAC broadcast */
909                 syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
910                                 dhcpv4_msg_to_string(msg),
911                                 inet_ntoa(dest.sin_addr));
912         else
913                 /*
914                  * reply is send directly to IP,
915                  * MAC is assumed to be the same as the request
916                  */
917                 syslog(LOG_WARNING, "sending %s to %02x:%02x:%02x:%02x:%02x:%02x - %s",
918                                 dhcpv4_msg_to_string(msg),
919                                 req->chaddr[0],req->chaddr[1],req->chaddr[2],
920                                 req->chaddr[3],req->chaddr[4],req->chaddr[5],
921                                 inet_ntoa(dest.sin_addr));
922
923         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
924                         (struct sockaddr*)&dest, sizeof(dest));
925
926 #ifdef WITH_UBUS
927         if (msg == DHCPV4_MSG_ACK)
928                 ubus_bcast_dhcp_event("dhcp.ack", req->chaddr, req->hlen, &reply.yiaddr,
929                                         hostname, iface->ifname);
930 #endif
931 }
932
933 static bool dhcpv4_assign(struct interface *iface,
934                 struct dhcpv4_assignment *assign, uint32_t raddr)
935 {
936         uint32_t start = ntohl(iface->dhcpv4_start_ip.s_addr);
937         uint32_t end = ntohl(iface->dhcpv4_end_ip.s_addr);
938         uint32_t count = end - start + 1;
939
940         // try to assign the IP the client asked for
941         if (start <= ntohl(raddr) && ntohl(raddr) <= end &&
942                         !find_assignment_by_addr(iface, raddr)) {
943                 assign->addr = raddr;
944                 syslog(LOG_INFO, "assigning the IP the client asked for: %u.%u.%u.%u",
945                                 ((uint8_t *)&assign->addr)[0],
946                                 ((uint8_t *)&assign->addr)[1],
947                                 ((uint8_t *)&assign->addr)[2],
948                                 ((uint8_t *)&assign->addr)[3]);
949                 return true;
950         }
951
952         // Seed RNG with checksum of hwaddress
953         uint32_t seed = 0;
954         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
955                 // Knuth's multiplicative method
956                 uint8_t o = assign->hwaddr[i];
957                 seed += (o*2654435761) % UINT32_MAX;
958         }
959
960         srand(seed);
961
962         uint32_t try = (((uint32_t)rand()) % count) + start;
963
964         if (list_empty(&iface->dhcpv4_assignments)) {
965                 assign->addr = htonl(try);
966                 syslog(LOG_INFO, "assigning mapped IP (empty list): %u.%u.%u.%u",
967                                 ((uint8_t *)&assign->addr)[0],
968                                 ((uint8_t *)&assign->addr)[1],
969                                 ((uint8_t *)&assign->addr)[2],
970                                 ((uint8_t *)&assign->addr)[3]);
971                 return true;
972         }
973
974         for (uint32_t i = 0; i < count; ++i) {
975                 if (!find_assignment_by_addr(iface, htonl(try))) {
976                         /* test was successful: IP address is not assigned, assign it */
977                         assign->addr = htonl(try);
978                         syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
979                                         ((uint8_t *)&assign->addr)[0],
980                                         ((uint8_t *)&assign->addr)[1],
981                                         ((uint8_t *)&assign->addr)[2],
982                                         ((uint8_t *)&assign->addr)[3],
983                                         i, count);
984                         return true;
985                 }
986                 try = (((try - start) + 1) % count) + start;
987         }
988
989         syslog(LOG_WARNING, "can't assign any IP address -> address space is full");
990         return false;
991 }
992
993
994 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
995                 enum dhcpv4_msg msg, const uint8_t *mac, const uint32_t reqaddr,
996                 uint32_t *leasetime, const char *hostname, const size_t hostname_len,
997                 const bool accept_fr_nonce, bool *incl_fr_opt, uint32_t *fr_serverid)
998 {
999         struct dhcpv4_assignment *a = find_assignment_by_hwaddr(iface, mac);
1000         struct dhcpv4_assignment *lease = NULL;
1001         time_t now = odhcpd_time();
1002
1003         if (a && (a->flags & OAF_BOUND) && a->fr_ip) {
1004                 *fr_serverid = a->fr_ip->addr.addr.in.s_addr;
1005                 dhcpv4_fr_stop(a);
1006         }
1007
1008         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
1009                 bool assigned = !!a;
1010
1011                 if (!a) {
1012                         if (!iface->no_dynamic_dhcp) {
1013                                 /* Create new binding */
1014                                 a = calloc(1, sizeof(*a));
1015                                 if (!a) {
1016                                         syslog(LOG_ERR, "Failed to calloc binding on interface %s",
1017                                                         iface->ifname);
1018                                         return NULL;
1019                                 }
1020                                 memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
1021                                 /* Don't consider new assignment as infinite */
1022                                 a->valid_until = now;
1023
1024                                 assigned = dhcpv4_assign(iface, a, reqaddr);
1025                                 if (assigned) {
1026                                         a->iface = iface;
1027                                         list_add(&a->head, &iface->dhcpv4_assignments);
1028                                 }
1029                         }
1030                 } else if ((a->addr & iface->dhcpv4_mask.s_addr) !=
1031                                 (iface->dhcpv4_start_ip.s_addr & iface->dhcpv4_mask.s_addr)) {
1032                         list_del(&a->head);
1033
1034                         assigned = dhcpv4_assign(iface, a, reqaddr);
1035                         if (assigned)
1036                                 list_add(&a->head, &iface->dhcpv4_assignments);
1037                 }
1038
1039                 if (assigned) {
1040                         uint32_t my_leasetime;
1041
1042                         if (a->leasetime)
1043                                 my_leasetime = a->leasetime;
1044                         else
1045                                 my_leasetime = iface->dhcpv4_leasetime;
1046
1047                         if ((*leasetime == 0) || (my_leasetime < *leasetime))
1048                                 *leasetime = my_leasetime;
1049
1050                         if (msg == DHCPV4_MSG_DISCOVER) {
1051                                 a->flags &= ~OAF_BOUND;
1052
1053                                 *incl_fr_opt = accept_fr_nonce;
1054                                 if (!(a->flags & OAF_STATIC))
1055                                         a->valid_until = now;
1056                         } else {
1057                                 if (hostname_len > 0) {
1058                                         a->hostname = realloc(a->hostname, hostname_len + 1);
1059                                         if (a->hostname) {
1060                                                 memcpy(a->hostname, hostname, hostname_len);
1061                                                 a->hostname[hostname_len] = 0;
1062                                         }
1063                                 }
1064
1065                                 if (!(a->flags & OAF_BOUND)) {
1066                                         a->accept_fr_nonce = accept_fr_nonce;
1067                                         *incl_fr_opt = accept_fr_nonce;
1068                                         odhcpd_urandom(a->key, sizeof(a->key));
1069                                         a->flags |= OAF_BOUND;
1070                                 } else
1071                                         *incl_fr_opt = false;
1072
1073                                 if (!(a->flags & OAF_STATIC))
1074                                         a->valid_until = ((*leasetime == UINT32_MAX) ? 0 : (time_t)(now + *leasetime));
1075                         }
1076                 } else if (!assigned && a) {
1077                         /* Cleanup failed assignment */
1078                         free_dhcpv4_assignment(a);
1079                         a = NULL;
1080                 }
1081
1082                 if (assigned && a)
1083                         lease = a;
1084         } else if (msg == DHCPV4_MSG_RELEASE && a) {
1085                 a->flags &= ~OAF_BOUND;
1086
1087                 if (!(a->flags & OAF_STATIC))
1088                         a->valid_until = now - 1;
1089
1090         } else if (msg == DHCPV4_MSG_DECLINE && a) {
1091                 a->flags &= ~OAF_BOUND;
1092
1093                 if (!(a->flags & OAF_STATIC)) {
1094                         memset(a->hwaddr, 0, sizeof(a->hwaddr));
1095                         a->valid_until = now + 3600; /* Block address for 1h */
1096                 }
1097         }
1098
1099         dhcpv6_write_statefile();
1100
1101         return lease;
1102 }