DHCPv4: Compile fix on 64bit Debian.
[project/odhcpd.git] / src / dhcpv4.c
1 /**
2  * Copyright (C) 2012-2013 Steven Barth <steven@midlink.org>
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License v2 as published by
6  * the Free Software Foundation.
7  *
8  * This program is distributed in the hope that it will be useful,
9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
11  * GNU General Public License for more details.
12  *
13  *
14  */
15
16 #include <time.h>
17 #include <errno.h>
18 #include <fcntl.h>
19 #include <unistd.h>
20 #include <stddef.h>
21 #include <stdlib.h>
22 #include <resolv.h>
23 #include <limits.h>
24 #include <net/if.h>
25 #include <net/if_arp.h>
26 #include <netinet/ip.h>
27 #include <sys/ioctl.h>
28 #include <sys/timerfd.h>
29 #include <arpa/inet.h>
30
31 #include "odhcpd.h"
32 #include "dhcpv4.h"
33 #include "dhcpv6.h"
34
35
36 static void handle_dhcpv4(void *addr, void *data, size_t len,
37                 struct interface *iface, void *dest_addr);
38 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
39                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
40                 const char *hostname);
41
42 // Create socket and register events
43 int init_dhcpv4(void)
44 {
45         return 0;
46 }
47
48 char *dhcpv4_msg_to_string(uint8_t reqmsg)
49 {
50         switch (reqmsg) {
51         case (DHCPV4_MSG_DISCOVER):
52                 return "DHCPV4_MSG_DISCOVER";
53         case (DHCPV4_MSG_OFFER):
54                 return "DHCPV4_MSG_OFFER";
55         case (DHCPV4_MSG_REQUEST):
56                 return "DHCPV4_MSG_REQUEST";
57         case (DHCPV4_MSG_DECLINE):
58                 return "DHCPV4_MSG_DECLINE";
59         case (DHCPV4_MSG_ACK):
60                 return "DHCPV4_MSG_ACK";
61         case (DHCPV4_MSG_NAK):
62                 return "DHCPV4_MSG_NAK";
63         case (DHCPV4_MSG_RELEASE):
64                 return "DHCPV4_MSG_RELEASE";
65         case (DHCPV4_MSG_INFORM):
66                 return "DHCPV4_MSG_INFORM";
67         default:
68                 return "UNKNOWN";
69         }
70 }
71
72 int setup_dhcpv4_interface(struct interface *iface, bool enable)
73 {
74         if (iface->dhcpv4_event.uloop.fd > 0) {
75                 uloop_fd_delete(&iface->dhcpv4_event.uloop);
76                 close(iface->dhcpv4_event.uloop.fd);
77                 iface->dhcpv4_event.uloop.fd = -1;
78         }
79
80         if (iface->dhcpv4 && enable) {
81                 if (!iface->dhcpv4_assignments.next)
82                         INIT_LIST_HEAD(&iface->dhcpv4_assignments);
83
84                 int sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
85                 if (sock < 0) {
86                         syslog(LOG_ERR, "Failed to create DHCPv4 server socket: %s",
87                                         strerror(errno));
88                         return -1;
89                 }
90
91                 // Basic IPv6 configuration
92                 int val = 1;
93                 setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
94                 setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &val, sizeof(val));
95                 setsockopt(sock, IPPROTO_IP, IP_PKTINFO, &val, sizeof(val));
96
97                 val = IPTOS_PREC_INTERNETCONTROL;
98                 setsockopt(sock, IPPROTO_IP, IP_TOS, &val, sizeof(val));
99
100                 val = IP_PMTUDISC_DONT;
101                 setsockopt(sock, IPPROTO_IP, IP_MTU_DISCOVER, &val, sizeof(val));
102
103                 setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
104                                 iface->ifname, strlen(iface->ifname));
105
106                 struct sockaddr_in bind_addr = {AF_INET, htons(DHCPV4_SERVER_PORT),
107                                         {INADDR_ANY}, {0}};
108
109                 if (bind(sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr))) {
110                         syslog(LOG_ERR, "Failed to open DHCPv4 server socket: %s",
111                                         strerror(errno));
112                         return -1;
113                 }
114
115
116                 if (ntohl(iface->dhcpv4_start.s_addr) > ntohl(iface->dhcpv4_end.s_addr)) {
117                         syslog(LOG_ERR, "Invalid DHCP range");
118                         return -1;
119                 }
120
121                 // Create a range if not specified
122                 struct ifreq ifreq;
123                 strncpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
124
125                 struct sockaddr_in *saddr = (struct sockaddr_in*)&ifreq.ifr_addr;
126                 struct sockaddr_in *smask = (struct sockaddr_in*)&ifreq.ifr_netmask;
127                 if (!(iface->dhcpv4_start.s_addr & htonl(0xffff0000)) &&
128                                 !(iface->dhcpv4_end.s_addr & htonl(0xffff0000)) &&
129                                 !ioctl(sock, SIOCGIFADDR, &ifreq)) {
130                         struct in_addr addr = saddr->sin_addr;
131
132                         ioctl(sock, SIOCGIFNETMASK, &ifreq);
133                         struct in_addr mask = smask->sin_addr;
134
135                         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
136                         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
137
138                         if (start && end && start < end &&
139                                         start > ntohl(addr.s_addr & ~mask.s_addr) &&
140                                         (start & ntohl(~mask.s_addr)) == start &&
141                                         (end & ntohl(~mask.s_addr)) == end) {
142                                 iface->dhcpv4_start.s_addr = htonl(start) |
143                                                 (addr.s_addr & mask.s_addr);
144                                 iface->dhcpv4_end.s_addr = htonl(end) |
145                                                 (addr.s_addr & mask.s_addr);
146                         } else if (ntohl(mask.s_addr) <= 0xfffffff0) {
147                                 start = addr.s_addr & mask.s_addr;
148                                 end = addr.s_addr & mask.s_addr;
149
150                                 if (ntohl(mask.s_addr) <= 0xffffff00) {
151                                         iface->dhcpv4_start.s_addr = start | htonl(100);
152                                         iface->dhcpv4_end.s_addr = end | htonl(250);
153                                 } else if (ntohl(mask.s_addr) <= 0xffffffc0) {
154                                         iface->dhcpv4_start.s_addr = start | htonl(10);
155                                         iface->dhcpv4_end.s_addr = end | htonl(60);
156                                 } else if (ntohl(mask.s_addr) <= 0xffffffe0) {
157                                         iface->dhcpv4_start.s_addr = start | htonl(10);
158                                         iface->dhcpv4_end.s_addr = end | htonl(30);
159                                 } else {
160                                         iface->dhcpv4_start.s_addr = start | htonl(3);
161                                         iface->dhcpv4_end.s_addr = end | htonl(12);
162                                 }
163                         }
164
165
166                 }
167
168                 // Parse static entries
169                 struct lease *lease;
170                 list_for_each_entry(lease, &leases, head) {
171                         // Construct entry
172                         size_t hostlen = strlen(lease->hostname) + 1;
173                         struct dhcpv4_assignment *a = calloc(1, sizeof(*a) + hostlen);
174                         if (!a) {
175                                 syslog(LOG_ERR, "Calloc failed for static lease on interface %s",
176                                         iface->ifname);
177                                 return -1;
178                         }
179                         a->addr = ntohl(lease->ipaddr.s_addr);
180                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
181                         memcpy(a->hostname, lease->hostname, hostlen);
182                         a->valid_until = LONG_MAX;
183
184                         // Assign to all interfaces
185                         struct dhcpv4_assignment *c;
186                         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
187                                 if (c->addr > a->addr) {
188                                         list_add_tail(&a->head, &c->head);
189                                         break;
190                                 } else if (c->addr == a->addr) {
191                                         // Already an assignment with that number
192                                         break;
193                                 }
194                         }
195                         if (&c->head == &iface->dhcpv4_assignments) {
196                                 list_add(&a->head, &iface->dhcpv4_assignments);
197                         }
198
199                         if (!a->head.next)
200                                 free(a);
201                 }
202
203                 // Clean invalid assignments
204                 struct dhcpv4_assignment *a, *n;
205                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
206                         if ((htonl(a->addr) & smask->sin_addr.s_addr) !=
207                                         (iface->dhcpv4_start.s_addr & smask->sin_addr.s_addr)) {
208                                 list_del(&a->head);
209                                 free(a);
210                         }
211                 }
212
213
214                 if (iface->dhcpv4_leasetime < 60)
215                         iface->dhcpv4_leasetime = 43200;
216
217                 iface->dhcpv4_event.uloop.fd = sock;
218                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
219                 odhcpd_register(&iface->dhcpv4_event);
220         } else if (iface->dhcpv4_assignments.next) {
221                 while (!list_empty(&iface->dhcpv4_assignments)) {
222                         struct dhcpv4_assignment *a = list_first_entry(&iface->dhcpv4_assignments,
223                                         struct dhcpv4_assignment, head);
224                         list_del(&a->head);
225                         free(a->hostname);
226                         free(a);
227                 }
228
229         }
230         return 0;
231 }
232
233
234 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
235                 uint8_t type, uint8_t len, const void *data)
236 {
237         uint8_t *c = *cookie;
238         if (*cookie + 2 + len > (uint8_t*)&msg[1])
239                 return;
240
241         *c++ = type;
242         *c++ = len;
243         memcpy(c, data, len);
244
245         *cookie = c + len;
246 }
247
248
249 // Simple DHCPv6-server for information requests
250 static void handle_dhcpv4(void *addr, void *data, size_t len,
251                 struct interface *iface, _unused void *dest_addr)
252 {
253         if (!iface->dhcpv4)
254                 return;
255
256         struct dhcpv4_message *req = data;
257         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
258                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
259                 return;
260
261         int sock = iface->dhcpv4_event.uloop.fd;
262         struct sockaddr_in ifaddr;
263         struct sockaddr_in ifnetmask;
264
265         syslog(LOG_NOTICE, "Got DHCPv4 request");
266
267         struct ifreq ifreq;
268         memcpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
269         if (ioctl(sock, SIOCGIFADDR, &ifreq)) {
270                 syslog(LOG_WARNING, "DHCPv4 failed to detect address: %s", strerror(errno));
271                 return;
272         }
273
274         memcpy(&ifaddr, &ifreq.ifr_addr, sizeof(ifaddr));
275         if (ioctl(sock, SIOCGIFNETMASK, &ifreq))
276                 return;
277
278         memcpy(&ifnetmask, &ifreq.ifr_netmask, sizeof(ifnetmask));
279         uint32_t network = ifaddr.sin_addr.s_addr & ifnetmask.sin_addr.s_addr;
280
281         if ((iface->dhcpv4_start.s_addr & ifnetmask.sin_addr.s_addr) != network ||
282                         (iface->dhcpv4_end.s_addr & ifnetmask.sin_addr.s_addr) != network) {
283                 syslog(LOG_WARNING, "DHCPv4 range out of assigned network");
284                 return;
285         }
286
287         struct ifreq ifr = {.ifr_name = ""};
288         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
289
290         struct dhcpv4_message reply = {
291                 .op = DHCPV4_BOOTREPLY,
292                 .htype = 1,
293                 .hlen = 6,
294                 .hops = 0,
295                 .xid = req->xid,
296                 .secs = 0,
297                 .flags = req->flags,
298                 .ciaddr = {INADDR_ANY},
299                 .giaddr = req->giaddr,
300                 .siaddr = ifaddr.sin_addr,
301         };
302         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
303
304         reply.options[0] = 0x63;
305         reply.options[1] = 0x82;
306         reply.options[2] = 0x53;
307         reply.options[3] = 0x63;
308
309         uint8_t *cookie = &reply.options[4];
310         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
311         uint8_t msg = DHCPV4_MSG_ACK;
312
313         struct in_addr reqaddr = {INADDR_ANY};
314         char hostname[256];
315         hostname[0] = 0;
316
317         uint8_t *start = &req->options[4];
318         uint8_t *end = ((uint8_t*)data) + len;
319         struct dhcpv4_option *opt;
320         dhcpv4_for_each_option(start, end, opt) {
321                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1) {
322                         reqmsg = opt->data[0];
323                 } else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
324                         memcpy(hostname, opt->data, opt->len);
325                         hostname[opt->len] = 0;
326                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4) {
327                         memcpy(&reqaddr, opt->data, 4);
328                 } else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
329                         if (memcmp(opt->data, &ifaddr.sin_addr, 4))
330                                 return;
331                 } else if (iface->filter_class && opt->type == DHCPV4_OPT_USER_CLASS) {
332                         uint8_t *c = opt->data, *cend = &opt->data[opt->len];
333                         for (; c < cend && &c[*c] < cend; c = &c[1 + *c]) {
334                                 size_t elen = strlen(iface->filter_class);
335                                 if (*c == elen && !memcmp(&c[1], iface->filter_class, elen))
336                                         return; // Ignore from homenet
337                         }
338                 }
339         }
340
341         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
342                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
343                         reqmsg != DHCPV4_MSG_RELEASE)
344                 return;
345
346         struct dhcpv4_assignment *lease = NULL;
347         if (reqmsg != DHCPV4_MSG_INFORM)
348                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr, hostname);
349
350         if (!lease) {
351                 if (reqmsg == DHCPV4_MSG_REQUEST)
352                         msg = DHCPV4_MSG_NAK;
353                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
354                         return;
355         } else if (reqmsg == DHCPV4_MSG_DISCOVER) {
356                 msg = DHCPV4_MSG_OFFER;
357         } else if (reqmsg == DHCPV4_MSG_REQUEST && reqaddr.s_addr &&
358                         reqaddr.s_addr != htonl(lease->addr)) {
359                 msg = DHCPV4_MSG_NAK;
360                 /*
361                  * DHCP client requested an IP which we can't offer to him. Probably the
362                  * client changed the network. The reply type is set to DHCPV4_MSG_NAK,
363                  * because the client should not use that IP.
364                  *
365                  * For modern devices we build an answer that includes a valid IP, like
366                  * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
367                  * perform additional DHCP round trips.
368                  *
369                  */
370         }
371
372         syslog(LOG_WARNING, "received %s from %x:%x:%x:%x:%x:%x",
373                         dhcpv4_msg_to_string(reqmsg),
374                         req->chaddr[0],req->chaddr[1],req->chaddr[2],
375                         req->chaddr[3],req->chaddr[4],req->chaddr[5]);
376
377         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
378                 return;
379
380         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
381         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &ifaddr.sin_addr);
382
383         if (lease) {
384                 reply.yiaddr.s_addr = htonl(lease->addr);
385
386                 uint32_t val = htonl(iface->dhcpv4_leasetime);
387                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
388
389                 val = htonl(500 * iface->dhcpv4_leasetime / 1000);
390                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
391
392                 val = htonl(875 * iface->dhcpv4_leasetime / 1000);
393                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
394
395                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &ifnetmask.sin_addr);
396
397                 if (lease->hostname[0])
398                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
399                                         strlen(lease->hostname), lease->hostname);
400
401                 if (!ioctl(sock, SIOCGIFBRDADDR, &ifr)) {
402                         struct sockaddr_in *ina = (struct sockaddr_in*)&ifr.ifr_broadaddr;
403                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &ina->sin_addr);
404                 }
405         }
406
407         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
408                 uint16_t mtu = htons(ifr.ifr_mtu);
409                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
410         }
411
412         if (iface->search && iface->search_len <= 255) {
413                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
414                                 iface->search_len, iface->search);
415         } else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
416                 uint8_t search_buf[256];
417                 int len = dn_comp(_res.dnsrch[0], search_buf,
418                                                 sizeof(search_buf), NULL, NULL);
419                 if (len > 0)
420                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SEARCH_DOMAIN,
421                                         len, search_buf);
422         }
423
424         if (iface->dhcpv4_router_cnt == 0)
425                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &ifaddr.sin_addr);
426         else
427                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
428                                 4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
429
430
431         if (iface->dhcpv4_dns_cnt == 0)
432                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &ifaddr.sin_addr);
433         else
434                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
435                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
436
437
438         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
439
440         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
441         if (req->giaddr.s_addr) {
442                 /*
443                  * relay agent is configured, send reply to the agent
444                  */
445                 dest.sin_addr = req->giaddr;
446                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
447         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
448                 /*
449                  * client has existing configuration (ciaddr is set) AND this address is
450                  * not the address it used for the dhcp message
451                  */
452                 dest.sin_addr = req->ciaddr;
453                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
454         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
455                         req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
456                 /*
457                  * client requests a broadcast reply OR we can't offer an IP
458                  */
459                 dest.sin_addr.s_addr = INADDR_BROADCAST;
460                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
461         } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
462                 /*
463                  * client has no previous configuration -> no IP, so we need to reply
464                  * with a broadcast packet
465                  */
466                 dest.sin_addr.s_addr = INADDR_BROADCAST;
467                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
468         } else {
469                 /*
470                  * send reply to the newly (in this proccess) allocated IP
471                  */
472                 dest.sin_addr = reply.yiaddr;
473                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
474
475                 struct arpreq arp = {.arp_flags = ATF_COM};
476                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
477                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
478                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
479                 ioctl(sock, SIOCSARP, &arp);
480         }
481
482         if (dest.sin_addr.s_addr == INADDR_BROADCAST) {
483                 /*
484                  * reply goes to IP broadcast -> MAC broadcast
485                  */
486                 syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
487                                 dhcpv4_msg_to_string(msg),
488                                 inet_ntoa(dest.sin_addr));
489         } else {
490                 /*
491                  * reply is send directly to IP,
492                  * MAC is assumed to be the same as the request
493                  */
494                 syslog(LOG_WARNING, "sending %s to %x:%x:%x:%x:%x:%x - %s",
495                                 dhcpv4_msg_to_string(msg),
496                                 req->chaddr[0],req->chaddr[1],req->chaddr[2],
497                                 req->chaddr[3],req->chaddr[4],req->chaddr[5],
498                                 inet_ntoa(dest.sin_addr));
499         }
500
501         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
502                         (struct sockaddr*)&dest, sizeof(dest));
503 }
504
505 static bool dhcpv4_test(struct interface *iface, uint32_t try)
506 {
507         struct dhcpv4_assignment *c;
508         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
509                 if (c->addr == try) {
510                         return false;
511                 }
512         }
513         return true;
514 }
515
516 static bool dhcpv4_assign(struct interface *iface,
517                 struct dhcpv4_assignment *assign, uint32_t raddr)
518 {
519         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
520         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
521         uint32_t count = end - start + 1;
522
523         // try to assign the IP the client asked for
524         if (start <= raddr && raddr <= end && dhcpv4_test(iface, raddr)) {
525                 assign->addr = raddr;
526                 list_add(&assign->head, &iface->dhcpv4_assignments);
527                 syslog(LOG_DEBUG, "assigning the IP the client asked for: %u.%u.%u.%u",
528                                 (assign->addr & 0xff000000) >> 24,
529                                 (assign->addr & 0x00ff0000) >> 16,
530                                 (assign->addr & 0x0000ff00) >> 8,
531                                 (assign->addr & 0x000000ff));
532                 return true;
533         }
534
535         // Seed RNG with checksum of hwaddress
536         uint32_t seed = 0;
537         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i) {
538                 // Knuth's multiplicative method
539                 uint8_t o = assign->hwaddr[i];
540                 seed += (o*2654435761) % UINT32_MAX;
541         }
542         srand(seed);
543
544         uint32_t try = (((uint32_t)rand()) % count) + start;
545
546         if (list_empty(&iface->dhcpv4_assignments)) {
547                 assign->addr = try;
548                 list_add(&assign->head, &iface->dhcpv4_assignments);
549                 syslog(LOG_DEBUG, "assigning mapped IP (empty list): %u.%u.%u.%u",
550                                 (assign->addr & 0xff000000) >> 24,
551                                 (assign->addr & 0x00ff0000) >> 16,
552                                 (assign->addr & 0x0000ff00) >> 8,
553                                 (assign->addr & 0x000000ff));
554                 return true;
555         }
556
557         for (uint32_t i = 0; i < count; ++i) {
558                 if (dhcpv4_test(iface, try)) {
559                         /* test was successful: IP address is not assigned, assign it */
560                         assign->addr = try;
561                         list_add(&assign->head, &iface->dhcpv4_assignments);
562                         syslog(LOG_DEBUG, "assigning mapped IP: %u.%u.%u.%u (try %u of %u)",
563                                         (assign->addr & 0xff000000) >> 24,
564                                         (assign->addr & 0x00ff0000) >> 16,
565                                         (assign->addr & 0x0000ff00) >> 8,
566                                         (assign->addr & 0x000000ff), i, count);
567                         return true;
568                 }
569                 try = (((try - start) + 1) % count) + start;
570         }
571
572         syslog(LOG_DEBUG, "can't assign any IP address -> address space is full");
573         return false;
574 }
575
576
577 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
578                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
579                 const char *hostname)
580 {
581         struct dhcpv4_assignment *lease = NULL;
582         uint32_t raddr = ntohl(reqaddr.s_addr);
583         time_t now = odhcpd_time();
584
585         struct dhcpv4_assignment *c, *n, *a = NULL;
586         list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
587                 if (!memcmp(c->hwaddr, mac, 6)) {
588                         a = c;
589                         if (c->addr == raddr)
590                                 break;
591                 } else if (c->valid_until < now) {
592                         list_del(&c->head);
593                         free(c);
594                 }
595         }
596
597         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
598                 bool assigned = !!a;
599                 size_t hostlen = strlen(hostname) + 1;
600
601                 if (!a && !iface->no_dynamic_dhcp) { // Create new binding
602                         a = calloc(1, sizeof(*a) + hostlen);
603                         if (!a) {
604                                 syslog(LOG_ERR, "Failed to calloc binding on interface %s", iface->ifname);
605                                 return NULL;
606                         }
607                         memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
608                         memcpy(a->hostname, hostname, hostlen);
609
610                         assigned = dhcpv4_assign(iface, a, raddr);
611                 }
612
613                 if (assigned && !a->hostname[0] && hostname) {
614                         a = realloc(a, sizeof(*a) + hostlen);
615                         if (!a) {
616                                 syslog(LOG_ERR, "Failed to realloc binding on interface %s", iface->ifname);
617                                 return NULL;
618                         }
619                         memcpy(a->hostname, hostname, hostlen);
620
621                         // Fixup list
622                         a->head.next->prev = &a->head;
623                         a->head.prev->next = &a->head;
624                 }
625
626                 // Was only a solicitation: mark binding for removal
627                 if (assigned && a->valid_until < now) {
628                         a->valid_until = (msg == DHCPV4_MSG_DISCOVER) ? 0 :
629                                         (now + iface->dhcpv4_leasetime);
630                 } else if (!assigned && a) { // Cleanup failed assignment
631                         free(a);
632                         a = NULL;
633                 }
634
635                 if (assigned && a)
636                         lease = a;
637         } else if (msg == DHCPV4_MSG_RELEASE) {
638                 if (a && a->valid_until != LONG_MAX)
639                         a->valid_until = 0;
640         } else if (msg == DHCPV4_MSG_DECLINE && a->valid_until != LONG_MAX) {
641                 memset(a->hwaddr, 0, sizeof(a->hwaddr));
642                 a->valid_until = now + 3600; // Block address for 1h
643         }
644
645         dhcpv6_write_statefile();
646
647         return lease;
648 }
649