Minor fixes
[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 <net/if.h>
24 #include <net/if_arp.h>
25 #include <netinet/ip.h>
26 #include <sys/ioctl.h>
27 #include <sys/timerfd.h>
28 #include <arpa/inet.h>
29
30 #include "odhcpd.h"
31 #include "dhcpv4.h"
32 #include "dhcpv6.h"
33
34
35 static void handle_dhcpv4(void *addr, void *data, size_t len,
36                 struct interface *iface);
37 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
38                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
39                 const char *hostname);
40
41
42 // Create socket and register events
43 int init_dhcpv4(void)
44 {
45         return 0;
46 }
47
48
49 int setup_dhcpv4_interface(struct interface *iface, bool enable)
50 {
51         if (iface->dhcpv4_event.uloop.fd > 0) {
52                 uloop_fd_delete(&iface->dhcpv4_event.uloop);
53                 close(iface->dhcpv4_event.uloop.fd);
54                 iface->dhcpv4_event.uloop.fd = -1;
55         }
56
57         if (iface->dhcpv4 && enable) {
58                 if (!iface->dhcpv4_assignments.next)
59                         INIT_LIST_HEAD(&iface->dhcpv4_assignments);
60
61                 int sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
62
63                 // Basic IPv6 configuration
64                 int val = 1;
65                 setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
66                 setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &val, sizeof(val));
67                 setsockopt(sock, IPPROTO_IP, IP_PKTINFO, &val, sizeof(val));
68
69                 val = IPTOS_PREC_INTERNETCONTROL;
70                 setsockopt(sock, IPPROTO_IP, IP_TOS, &val, sizeof(val));
71
72                 val = IP_PMTUDISC_DONT;
73                 setsockopt(sock, IPPROTO_IP, IP_MTU_DISCOVER, &val, sizeof(val));
74
75                 setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
76                                 iface->ifname, strlen(iface->ifname));
77
78                 struct sockaddr_in bind_addr = {AF_INET, htons(DHCPV4_SERVER_PORT),
79                                         {INADDR_ANY}, {0}};
80
81                 if (bind(sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr))) {
82                         syslog(LOG_ERR, "Failed to open DHCPv4 server socket: %s",
83                                         strerror(errno));
84                         return -1;
85                 }
86
87
88                 if (ntohl(iface->dhcpv4_start.s_addr) > ntohl(iface->dhcpv4_end.s_addr)) {
89                         syslog(LOG_ERR, "Invalid DHCP range");
90                         return -1;
91                 }
92
93                 // Create a range if not specified
94                 struct ifreq ifreq;
95                 strncpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
96
97                 struct sockaddr_in *saddr = (struct sockaddr_in*)&ifreq.ifr_addr;
98                 struct sockaddr_in *smask = (struct sockaddr_in*)&ifreq.ifr_netmask;
99                 if (!(iface->dhcpv4_start.s_addr & htonl(0xffff0000)) &&
100                                 !(iface->dhcpv4_end.s_addr & htonl(0xffff0000)) &&
101                                 !ioctl(sock, SIOCGIFADDR, &ifreq)) {
102                         struct in_addr addr = saddr->sin_addr;
103
104                         ioctl(sock, SIOCGIFNETMASK, &ifreq);
105                         struct in_addr mask = smask->sin_addr;
106
107                         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
108                         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
109
110                         if (start && end && start < end &&
111                                         start > ntohl(addr.s_addr & ~mask.s_addr) &&
112                                         (start & ntohl(mask.s_addr)) == start &&
113                                         (end & ntohl(mask.s_addr)) == end) {
114                                 iface->dhcpv4_start.s_addr = htonl(start) |
115                                                 (addr.s_addr & mask.s_addr);
116                                 iface->dhcpv4_end.s_addr = htonl(end) |
117                                                 (addr.s_addr & mask.s_addr);
118                         } else if (ntohl(mask.s_addr) <= 0xffffffc0) {
119                                 start = addr.s_addr & mask.s_addr;
120                                 end = addr.s_addr & mask.s_addr;
121
122                                 if (ntohl(mask.s_addr) <= 0xffffff00) {
123                                         iface->dhcpv4_start.s_addr = start | htonl(100);
124                                         iface->dhcpv4_end.s_addr = end | htonl(250);
125                                 } else {
126                                         iface->dhcpv4_start.s_addr = start | htonl(10);
127                                         iface->dhcpv4_end.s_addr = end | htonl(59);
128                                 }
129                         }
130
131
132                 }
133
134                 // Parse static entries
135                 struct lease *lease;
136                 list_for_each_entry(lease, &leases, head) {
137                         // Construct entry
138                         size_t hostlen = strlen(lease->hostname) + 1;
139                         struct dhcpv4_assignment *a = calloc(1, sizeof(*a) + hostlen);
140
141                         a->addr = ntohl(lease->ipaddr.s_addr);
142                         memcpy(a->hwaddr, lease->mac.ether_addr_octet, sizeof(a->hwaddr));
143                         memcpy(a->hostname, lease->hostname, hostlen);
144
145                         // Assign to all interfaces
146                         struct dhcpv4_assignment *c;
147                         list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
148                                 if (c->addr > a->addr) {
149                                         list_add_tail(&a->head, &c->head);
150                                 } else if (c->addr == a->addr) {
151                                         // Already an assignment with that number
152                                         break;
153                                 }
154                         }
155
156                         if (!a->head.next)
157                                 free(a);
158                 }
159
160                 // Clean invalid assignments
161                 struct dhcpv4_assignment *a, *n;
162                 list_for_each_entry_safe(a, n, &iface->dhcpv4_assignments, head) {
163                         if ((htonl(a->addr) & smask->sin_addr.s_addr) !=
164                                         (saddr->sin_addr.s_addr & smask->sin_addr.s_addr)) {
165                                 list_del(&a->head);
166                                 free(a);
167                         }
168                 }
169
170
171                 if (iface->dhcpv4_leasetime < 60)
172                         iface->dhcpv4_leasetime = 43200;
173
174                 iface->dhcpv4_event.uloop.fd = sock;
175                 iface->dhcpv4_event.handle_dgram = handle_dhcpv4;
176                 odhcpd_register(&iface->dhcpv4_event);
177         } else if (iface->dhcpv4_assignments.next) {
178                 while (!list_empty(&iface->dhcpv4_assignments)) {
179                         struct dhcpv4_assignment *a = list_first_entry(&iface->dhcpv4_assignments,
180                                         struct dhcpv4_assignment, head);
181                         list_del(&a->head);
182                         free(a->hostname);
183                         free(a);
184                 }
185
186         }
187         return 0;
188 }
189
190
191 static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
192                 uint8_t type, uint8_t len, const void *data)
193 {
194         uint8_t *c = *cookie;
195         if (*cookie + 2 + len > (uint8_t*)&msg[1])
196                 return;
197
198         *c++ = type;
199         *c++ = len;
200         memcpy(c, data, len);
201
202         *cookie = c + len;
203 }
204
205
206 // Simple DHCPv6-server for information requests
207 static void handle_dhcpv4(void *addr, void *data, size_t len,
208                 struct interface *iface)
209 {
210         if (!iface->dhcpv4)
211                 return;
212
213         struct dhcpv4_message *req = data;
214         if (len < offsetof(struct dhcpv4_message, options) + 4 ||
215                         req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
216                 return;
217
218         int sock = iface->dhcpv4_event.uloop.fd;
219         struct sockaddr_in ifaddr;
220         struct sockaddr_in ifnetmask;
221
222         syslog(LOG_NOTICE, "Got DHCPv4 request");
223
224         struct ifreq ifreq;
225         memcpy(ifreq.ifr_name, iface->ifname, sizeof(ifreq.ifr_name));
226         if (ioctl(sock, SIOCGIFADDR, &ifreq)) {
227                 syslog(LOG_WARNING, "DHCPv4 failed to detect address: %s", strerror(errno));
228                 return;
229         }
230
231         memcpy(&ifaddr, &ifreq.ifr_addr, sizeof(ifaddr));
232         if (ioctl(sock, SIOCGIFNETMASK, &ifreq))
233                 return;
234
235         memcpy(&ifnetmask, &ifreq.ifr_netmask, sizeof(ifnetmask));
236         uint32_t network = ifaddr.sin_addr.s_addr & ifnetmask.sin_addr.s_addr;
237
238         if ((iface->dhcpv4_start.s_addr & ifnetmask.sin_addr.s_addr) != network ||
239                         (iface->dhcpv4_end.s_addr & ifnetmask.sin_addr.s_addr) != network) {
240                 syslog(LOG_WARNING, "DHCPv4 range out of assigned network");
241                 return;
242         }
243
244         struct ifreq ifr = {.ifr_name = ""};
245         strncpy(ifr.ifr_name, iface->ifname, sizeof(ifr.ifr_name));
246
247         struct dhcpv4_message reply = {
248                 .op = DHCPV4_BOOTREPLY,
249                 .htype = 1,
250                 .hlen = 6,
251                 .hops = 0,
252                 .xid = req->xid,
253                 .secs = 0,
254                 .flags = req->flags,
255                 .ciaddr = {INADDR_ANY},
256                 .giaddr = req->giaddr,
257                 .siaddr = ifaddr.sin_addr,
258         };
259         memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
260
261         reply.options[0] = 0x63;
262         reply.options[1] = 0x82;
263         reply.options[2] = 0x53;
264         reply.options[3] = 0x63;
265
266         uint8_t *cookie = &reply.options[4];
267         uint8_t reqmsg = DHCPV4_MSG_REQUEST;
268         uint8_t msg = DHCPV4_MSG_ACK;
269
270         struct in_addr reqaddr = {INADDR_ANY};
271         char hostname[256];
272         hostname[0] = 0;
273
274         uint8_t *start = &req->options[4];
275         uint8_t *end = ((uint8_t*)data) + len;
276         struct dhcpv4_option *opt;
277         dhcpv4_for_each_option(start, end, opt) {
278                 if (opt->type == DHCPV4_OPT_MESSAGE && opt->len == 1) {
279                         reqmsg = opt->data[0];
280                 } else if (opt->type == DHCPV4_OPT_HOSTNAME && opt->len > 0) {
281                         memcpy(hostname, opt->data, opt->len);
282                         hostname[opt->len] = 0;
283                 } else if (opt->type == DHCPV4_OPT_IPADDRESS && opt->len == 4) {
284                         memcpy(&reqaddr, opt->data, 4);
285                 } else if (opt->type == DHCPV4_OPT_SERVERID && opt->len == 4) {
286                         if (memcmp(opt->data, &ifaddr.sin_addr, 4))
287                                 return;
288                 }
289         }
290
291         if (reqmsg != DHCPV4_MSG_DISCOVER && reqmsg != DHCPV4_MSG_REQUEST &&
292                         reqmsg != DHCPV4_MSG_INFORM && reqmsg != DHCPV4_MSG_DECLINE &&
293                         reqmsg != DHCPV4_MSG_RELEASE)
294                 return;
295
296         struct dhcpv4_assignment *lease = NULL;
297         if (reqmsg != DHCPV4_MSG_INFORM)
298                 lease = dhcpv4_lease(iface, reqmsg, req->chaddr, reqaddr, hostname);
299
300         if (!lease) {
301                 if (reqmsg == DHCPV4_MSG_REQUEST)
302                         msg = DHCPV4_MSG_NAK;
303                 else if (reqmsg == DHCPV4_MSG_DISCOVER)
304                         return;
305         } else if (reqmsg == DHCPV4_MSG_DISCOVER) {
306                 msg = DHCPV4_MSG_OFFER;
307         }
308
309         if (reqmsg == DHCPV4_MSG_DECLINE || reqmsg == DHCPV4_MSG_RELEASE)
310                 return;
311
312         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
313         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_SERVERID, 4, &ifaddr.sin_addr);
314
315         if (lease) {
316                 reply.yiaddr.s_addr = htonl(lease->addr);
317
318                 uint32_t val = htonl(iface->dhcpv4_leasetime);
319                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_LEASETIME, 4, &val);
320
321                 val = htonl(500 * iface->dhcpv4_leasetime / 1000);
322                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_RENEW, 4, &val);
323
324                 val = htonl(875 * iface->dhcpv4_leasetime / 1000);
325                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_REBIND, 4, &val);
326
327                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_NETMASK, 4, &ifnetmask.sin_addr);
328
329                 if (lease->hostname[0])
330                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_HOSTNAME,
331                                         strlen(lease->hostname), lease->hostname);
332
333                 if (!ioctl(sock, SIOCGIFBRDADDR, &ifr)) {
334                         struct sockaddr_in *ina = (struct sockaddr_in*)&ifr.ifr_broadaddr;
335                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_BROADCAST, 4, &ina->sin_addr);
336                 }
337         }
338
339         if (!ioctl(sock, SIOCGIFMTU, &ifr)) {
340                 uint16_t mtu = htons(ifr.ifr_mtu);
341                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_MTU, 2, &mtu);
342         }
343
344         if (iface->search) {
345                 char b[256];
346                 if (dn_expand(iface->search, iface->search + iface->search_len,
347                                 iface->search, b, sizeof(b)) > 0)
348                         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DOMAIN, strlen(b), b);
349         } else if (!res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
350                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DOMAIN,
351                                 strlen(_res.dnsrch[0]), _res.dnsrch[0]);
352         }
353
354         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &ifaddr.sin_addr);
355
356
357
358         if (iface->dhcpv4_dns_cnt == 0)
359                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER, 4, &ifaddr.sin_addr);
360         else
361                 dhcpv4_put(&reply, &cookie, DHCPV4_OPT_DNSSERVER,
362                                 4 * iface->dhcpv4_dns_cnt, iface->dhcpv4_dns);
363
364
365         dhcpv4_put(&reply, &cookie, DHCPV4_OPT_END, 0, NULL);
366
367         struct sockaddr_in dest = *((struct sockaddr_in*)addr);
368         if (req->giaddr.s_addr) {
369                 dest.sin_addr = req->giaddr;
370                 dest.sin_port = htons(DHCPV4_SERVER_PORT);
371         } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
372                 dest.sin_addr = req->ciaddr;
373                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
374         } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
375                         req->hlen != reply.hlen) {
376                 dest.sin_addr.s_addr = INADDR_BROADCAST;
377                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
378         } else {
379                 dest.sin_addr = reply.yiaddr;
380                 dest.sin_port = htons(DHCPV4_CLIENT_PORT);
381
382                 struct arpreq arp = {.arp_flags = ATF_COM};
383                 memcpy(arp.arp_ha.sa_data, req->chaddr, 6);
384                 memcpy(&arp.arp_pa, &dest, sizeof(arp.arp_pa));
385                 memcpy(arp.arp_dev, iface->ifname, sizeof(arp.arp_dev));
386                 ioctl(sock, SIOCSARP, &arp);
387         }
388
389         sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
390                         (struct sockaddr*)&dest, sizeof(dest));
391 }
392
393
394 static bool dhcpv4_assign(struct interface *iface,
395                 struct dhcpv4_assignment *assign, uint32_t raddr)
396 {
397         const unsigned tries = 10;
398         uint32_t start = ntohl(iface->dhcpv4_start.s_addr);
399         uint32_t end = ntohl(iface->dhcpv4_end.s_addr);
400         uint32_t count = end - start + 1;
401
402         // Seed RNG with checksum of DUID
403         uint32_t seed = 0;
404         for (size_t i = 0; i < sizeof(assign->hwaddr); ++i)
405                 seed += assign->hwaddr[i];
406         srand(seed);
407
408         // Try to assign up to 100x
409         for (unsigned i = 0; i < tries; ++i) {
410                 uint32_t try = (((uint32_t)rand()) % count) + start;
411                 if (i == 0 && raddr >= start && raddr <= end)
412                         try = raddr;
413                 else if (i == tries - 1)
414                         try = start;
415
416                 if (list_empty(&iface->dhcpv4_assignments)) {
417                         assign->addr = try;
418                         list_add(&assign->head, &iface->dhcpv4_assignments);
419                         return true;
420                 }
421
422                 struct dhcpv4_assignment *c;
423                 list_for_each_entry(c, &iface->dhcpv4_assignments, head) {
424                         if (c->addr > try) {
425                                 assign->addr = try;
426                                 list_add_tail(&assign->head, &c->head);
427                                 return true;
428                         } else if (c->addr == try) {
429                                 if (i < tries - 1)
430                                         break;
431                                 else
432                                         ++try;
433                         }
434                 }
435         }
436
437         return false;
438 }
439
440
441 static struct dhcpv4_assignment* dhcpv4_lease(struct interface *iface,
442                 enum dhcpv4_msg msg, const uint8_t *mac, struct in_addr reqaddr,
443                 const char *hostname)
444 {
445         struct dhcpv4_assignment *lease = NULL;
446         uint32_t raddr = ntohl(reqaddr.s_addr);
447         time_t now = odhcpd_time();
448
449         struct dhcpv4_assignment *c, *n, *a = NULL;
450         list_for_each_entry_safe(c, n, &iface->dhcpv4_assignments, head) {
451                 if (c->addr == raddr && !memcmp(c->hwaddr, mac, 6)) {
452                         a = c;
453                         break;
454                 } else if (c->valid_until < now) {
455                         list_del(&c->head);
456                         free(c);
457                 }
458         }
459
460         bool update_state = false;
461         if (msg == DHCPV4_MSG_DISCOVER || msg == DHCPV4_MSG_REQUEST) {
462                 bool assigned = !!a;
463                 size_t hostlen = strlen(hostname) + 1;
464
465                 if (!a && !iface->no_dynamic_dhcp) { // Create new binding
466                         a = calloc(1, sizeof(*a) + hostlen);
467                         memcpy(a->hwaddr, mac, sizeof(a->hwaddr));
468                         memcpy(a->hostname, hostname, hostlen);
469
470                         assigned = dhcpv4_assign(iface, a, raddr);
471                 }
472
473                 if (assigned && !a->hostname[0] && hostname) {
474                         a = realloc(a, sizeof(*a) + hostlen);
475                         memcpy(a->hostname, hostname, hostlen);
476
477                         // Fixup list
478                         a->head.next->prev = &a->head;
479                         a->head.prev->next = &a->head;
480                 }
481
482                 // Was only a solicitation: mark binding for removal
483                 if (assigned && a->valid_until < now) {
484                         a->valid_until = (msg == DHCPV4_MSG_DISCOVER) ? 0 :
485                                         (now + iface->dhcpv4_leasetime);
486                 } else if (!assigned && a) { // Cleanup failed assignment
487                         free(a);
488                         a = NULL;
489                 }
490
491                 if (assigned && a)
492                         lease = a;
493         } else if (msg == DHCPV4_MSG_RELEASE) {
494                 if (a) {
495                         a->valid_until = 0;
496                         update_state = true;
497                 }
498         } else if (msg == DHCPV4_MSG_DECLINE) {
499                 memset(a->hwaddr, 0, sizeof(a->hwaddr));
500                 a->valid_until = now + 3600; // Block address for 1h
501                 update_state = true;
502         }
503
504         if (update_state)
505                 dhcpv6_write_statefile();
506
507         return lease;
508 }
509