treewide: reflect managed mode is related to RA
[project/odhcpd.git] / src / dhcpv6.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 <errno.h>
17 #include <unistd.h>
18 #include <stddef.h>
19 #include <resolv.h>
20 #include <sys/timerfd.h>
21 #include <arpa/inet.h>
22
23 #include "odhcpd.h"
24 #include "dhcpv6.h"
25
26
27 static void relay_client_request(struct sockaddr_in6 *source,
28                 const void *data, size_t len, struct interface *iface);
29 static void relay_server_response(uint8_t *data, size_t len);
30
31 static void handle_dhcpv6(void *addr, void *data, size_t len,
32                 struct interface *iface, void *dest);
33 static void handle_client_request(void *addr, void *data, size_t len,
34                 struct interface *iface, void *dest_addr);
35
36
37
38 // Create socket and register events
39 int init_dhcpv6(void)
40 {
41         dhcpv6_ia_init();
42         return 0;
43 }
44
45
46 int setup_dhcpv6_interface(struct interface *iface, bool enable)
47 {
48         if (iface->dhcpv6_event.uloop.fd > 0) {
49                 uloop_fd_delete(&iface->dhcpv6_event.uloop);
50                 close(iface->dhcpv6_event.uloop.fd);
51                 iface->dhcpv6_event.uloop.fd = -1;
52         }
53
54         // Configure multicast settings
55         if (enable && iface->dhcpv6) {
56                 int sock = socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
57                 if (sock < 0) {
58                         syslog(LOG_ERR, "Failed to create DHCPv6 server socket: %s",
59                                         strerror(errno));
60                         return -1;
61                 }
62
63                 // Basic IPv6 configuration
64                 setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE, iface->ifname, strlen(iface->ifname));
65
66                 int val = 1;
67                 setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, &val, sizeof(val));
68                 setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
69                 setsockopt(sock, IPPROTO_IPV6, IPV6_RECVPKTINFO, &val, sizeof(val));
70
71                 val = DHCPV6_HOP_COUNT_LIMIT;
72                 setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
73
74                 val = 0;
75                 setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &val, sizeof(val));
76
77                 struct sockaddr_in6 bind_addr = {AF_INET6, htons(DHCPV6_SERVER_PORT),
78                                         0, IN6ADDR_ANY_INIT, 0};
79
80                 if (bind(sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr))) {
81                         syslog(LOG_ERR, "Failed to open DHCPv6 server socket: %s",
82                                         strerror(errno));
83                         return -1;
84                 }
85
86                 struct ipv6_mreq relay = {ALL_DHCPV6_RELAYS, iface->ifindex};
87                 struct ipv6_mreq server = {ALL_DHCPV6_SERVERS, iface->ifindex};
88                 setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &relay, sizeof(relay));
89
90                 if (iface->dhcpv6 == RELAYD_SERVER)
91                         setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &server, sizeof(server));
92
93                 iface->dhcpv6_event.uloop.fd = sock;
94                 iface->dhcpv6_event.handle_dgram = handle_dhcpv6;
95                 odhcpd_register(&iface->dhcpv6_event);
96         }
97
98         return setup_dhcpv6_ia_interface(iface, enable);
99 }
100
101 enum {
102         IOV_NESTED = 0,
103         IOV_DEST,
104         IOV_MAXRT,
105 #define IOV_STAT IOV_MAXRT
106         IOV_DNS,
107         IOV_DNS_ADDR,
108         IOV_SEARCH,
109         IOV_SEARCH_DOMAIN,
110         IOV_PDBUF,
111 #define IOV_REFRESH IOV_PDBUF
112         IOV_CERID,
113         IOV_DHCPV6_RAW,
114         IOV_RELAY_MSG,
115         IOV_TOTAL
116 };
117
118 static void handle_nested_message(uint8_t *data, size_t len,
119                 uint8_t **opts, uint8_t **end, struct iovec iov[IOV_TOTAL - 1])
120 {
121         struct dhcpv6_relay_header *hdr = (struct dhcpv6_relay_header*)data;
122         if (iov[IOV_NESTED].iov_base == NULL) {
123                 iov[IOV_NESTED].iov_base = data;
124                 iov[IOV_NESTED].iov_len = len;
125         }
126
127         if (len < sizeof(struct dhcpv6_client_header))
128                 return;
129
130         if (hdr->msg_type != DHCPV6_MSG_RELAY_FORW) {
131                 iov[IOV_NESTED].iov_len = data - (uint8_t*)iov[IOV_NESTED].iov_base;
132                 struct dhcpv6_client_header *hdr = (void*)data;
133                 *opts = (uint8_t*)&hdr[1];
134                 *end = data + len;
135                 return;
136         }
137
138         uint16_t otype, olen;
139         uint8_t *odata;
140         dhcpv6_for_each_option(hdr->options, data + len, otype, olen, odata) {
141                 if (otype == DHCPV6_OPT_RELAY_MSG) {
142                         iov[IOV_RELAY_MSG].iov_base = odata + olen;
143                         iov[IOV_RELAY_MSG].iov_len = (((uint8_t*)iov[IOV_NESTED].iov_base) + 
144                                         iov[IOV_NESTED].iov_len) - (odata + olen);
145                         handle_nested_message(odata, olen, opts, end, iov);
146                         return;
147                 }
148         }
149 }
150
151
152 static void update_nested_message(uint8_t *data, size_t len, ssize_t pdiff)
153 {
154         struct dhcpv6_relay_header *hdr = (struct dhcpv6_relay_header*)data;
155         if (hdr->msg_type != DHCPV6_MSG_RELAY_FORW)
156                 return;
157
158         hdr->msg_type = DHCPV6_MSG_RELAY_REPL;
159
160         uint16_t otype, olen;
161         uint8_t *odata;
162         dhcpv6_for_each_option(hdr->options, data + len, otype, olen, odata) {
163                 if (otype == DHCPV6_OPT_RELAY_MSG) {
164                         olen += pdiff;
165                         odata[-2] = (olen >> 8) & 0xff;
166                         odata[-1] = olen & 0xff;
167                         update_nested_message(odata, olen - pdiff, pdiff);
168                         return;
169                 }
170         }
171 }
172
173 // Simple DHCPv6-server for information requests
174 static void handle_client_request(void *addr, void *data, size_t len,
175                 struct interface *iface, void *dest_addr)
176 {
177         struct dhcpv6_client_header *hdr = data;
178
179         if (len < sizeof(*hdr))
180                 return;
181
182         syslog(LOG_NOTICE, "Got DHCPv6 request");
183
184         // Construct reply message
185         struct __attribute__((packed)) {
186                 uint8_t msg_type;
187                 uint8_t tr_id[3];
188                 uint16_t serverid_type;
189                 uint16_t serverid_length;
190                 uint16_t duid_type;
191                 uint16_t hardware_type;
192                 uint8_t mac[6];
193                 uint16_t clientid_type;
194                 uint16_t clientid_length;
195                 uint8_t clientid_buf[130];
196         } dest = {
197                 .msg_type = DHCPV6_MSG_REPLY,
198                 .serverid_type = htons(DHCPV6_OPT_SERVERID),
199                 .serverid_length = htons(10),
200                 .duid_type = htons(3),
201                 .hardware_type = htons(1),
202                 .clientid_type = htons(DHCPV6_OPT_CLIENTID),
203                 .clientid_buf = {0}
204         };
205         odhcpd_get_mac(iface, dest.mac);
206
207         struct __attribute__((packed)) {
208                 uint16_t type;
209                 uint16_t len;
210                 uint32_t value;
211         } maxrt = {htons(DHCPV6_OPT_SOL_MAX_RT), htons(sizeof(maxrt) - 4),
212                         htonl(60)};
213
214         struct __attribute__((packed)) {
215                 uint16_t type;
216                 uint16_t len;
217                 uint16_t value;
218         } stat = {htons(DHCPV6_OPT_STATUS), htons(sizeof(stat) - 4),
219                         htons(DHCPV6_STATUS_USEMULTICAST)};
220
221         struct __attribute__((packed)) {
222                 uint16_t type;
223                 uint16_t len;
224                 uint32_t value;
225         } refresh = {htons(DHCPV6_OPT_INFO_REFRESH), htons(sizeof(uint32_t)),
226                         htonl(600)};
227
228         struct in6_addr dns_addr, *dns_addr_ptr = iface->dns;
229         size_t dns_cnt = iface->dns_cnt;
230
231         if ((dns_cnt == 0) &&
232                 !odhcpd_get_interface_dns_addr(iface, &dns_addr)) {
233                 dns_addr_ptr = &dns_addr;
234                 dns_cnt = 1;
235         }
236
237         struct {
238                 uint16_t type;
239                 uint16_t len;
240         } dns = {htons(DHCPV6_OPT_DNS_SERVERS), htons(dns_cnt * sizeof(*dns_addr_ptr))};
241
242
243
244         // DNS Search options
245         uint8_t search_buf[256], *search_domain = iface->search;
246         size_t search_len = iface->search_len;
247
248         if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
249                 int len = dn_comp(_res.dnsrch[0], search_buf,
250                                 sizeof(search_buf), NULL, NULL);
251                 if (len > 0) {
252                         search_domain = search_buf;
253                         search_len = len;
254                 }
255         }
256
257         struct {
258                 uint16_t type;
259                 uint16_t len;
260         } search = {htons(DHCPV6_OPT_DNS_DOMAIN), htons(search_len)};
261
262
263         struct dhcpv6_cer_id cerid = {
264 #ifdef EXT_CER_ID
265                 .type = htons(EXT_CER_ID),
266 #endif
267                 .len = htons(36),
268                 .addr = iface->dhcpv6_pd_cer,
269         };
270
271
272         uint8_t pdbuf[512];
273         struct iovec iov[IOV_TOTAL] = {
274                 [IOV_NESTED] = {NULL, 0},
275                 [IOV_DEST] = {&dest, (uint8_t*)&dest.clientid_type - (uint8_t*)&dest},
276                 [IOV_MAXRT] = {&maxrt, sizeof(maxrt)},
277                 [IOV_DNS] = {&dns, (dns_cnt) ? sizeof(dns) : 0},
278                 [IOV_DNS_ADDR] = {dns_addr_ptr, dns_cnt * sizeof(*dns_addr_ptr)},
279                 [IOV_SEARCH] = {&search, (search_len) ? sizeof(search) : 0},
280                 [IOV_SEARCH_DOMAIN] = {search_domain, search_len},
281                 [IOV_PDBUF] = {pdbuf, 0},
282                 [IOV_CERID] = {&cerid, 0},
283                 [IOV_DHCPV6_RAW] = {iface->dhcpv6_raw, iface->dhcpv6_raw_len},
284                 [IOV_RELAY_MSG] = {NULL, 0}
285         };
286
287         uint8_t *opts = (uint8_t*)&hdr[1], *opts_end = (uint8_t*)data + len;
288         if (hdr->msg_type == DHCPV6_MSG_RELAY_FORW)
289                 handle_nested_message(data, len, &opts, &opts_end, iov);
290
291         memcpy(dest.tr_id, &opts[-3], sizeof(dest.tr_id));
292
293         if (opts[-4] == DHCPV6_MSG_ADVERTISE || opts[-4] == DHCPV6_MSG_REPLY || opts[-4] == DHCPV6_MSG_RELAY_REPL)
294                 return;
295
296         if (!IN6_IS_ADDR_MULTICAST((struct in6_addr *)dest_addr) && iov[IOV_NESTED].iov_len == 0 &&
297                 (opts[-4] == DHCPV6_MSG_SOLICIT || opts[-4] == DHCPV6_MSG_CONFIRM ||
298                  opts[-4] == DHCPV6_MSG_REBIND || opts[-4] == DHCPV6_MSG_INFORMATION_REQUEST))
299                 return;
300
301         if (opts[-4] == DHCPV6_MSG_SOLICIT) {
302                 dest.msg_type = DHCPV6_MSG_ADVERTISE;
303         } else if (opts[-4] == DHCPV6_MSG_INFORMATION_REQUEST) {
304                 iov[IOV_REFRESH].iov_base = &refresh;
305                 iov[IOV_REFRESH].iov_len = sizeof(refresh);
306
307                 // Return inf max rt option in reply to information request
308                 maxrt.type = htons(DHCPV6_OPT_INF_MAX_RT);
309         }
310
311         // Go through options and find what we need
312         uint16_t otype, olen;
313         uint8_t *odata;
314         dhcpv6_for_each_option(opts, opts_end, otype, olen, odata) {
315                 if (otype == DHCPV6_OPT_CLIENTID && olen <= 130) {
316                         dest.clientid_length = htons(olen);
317                         memcpy(dest.clientid_buf, odata, olen);
318                         iov[IOV_DEST].iov_len += 4 + olen;
319                 } else if (otype == DHCPV6_OPT_SERVERID) {
320                         if (olen != ntohs(dest.serverid_length) ||
321                                         memcmp(odata, &dest.duid_type, olen))
322                                 return; // Not for us
323                 } else if (iface->filter_class && otype == DHCPV6_OPT_USER_CLASS) {
324                         uint8_t *c = odata, *cend = &odata[olen];
325                         for (; &c[2] <= cend && &c[2 + (c[0] << 8) + c[1]] <= cend; c = &c[2 + (c[0] << 8) + c[1]]) {
326                                 size_t elen = strlen(iface->filter_class);
327                                 if (((((size_t)c[0]) << 8) | c[1]) == elen && !memcmp(&c[2], iface->filter_class, elen))
328                                         return; // Ignore from homenet
329                         }
330                 } else if (otype == DHCPV6_OPT_IA_PD) {
331 #ifdef EXT_CER_ID
332                         iov[IOV_CERID].iov_len = sizeof(cerid);
333
334                         if (IN6_IS_ADDR_UNSPECIFIED(&cerid.addr)) {
335                                 struct odhcpd_ipaddr *addrs;
336                                 ssize_t len = odhcpd_get_interface_addresses(0, true, &addrs);
337
338                                 for (ssize_t i = 0; i < len; ++i)
339                                         if (IN6_IS_ADDR_UNSPECIFIED(&cerid.addr)
340                                                         || memcmp(&addrs[i].addr, &cerid.addr, sizeof(cerid.addr)) < 0)
341                                                 cerid.addr = addrs[i].addr;
342
343                                 free(addrs);
344                         }
345 #endif
346                 }
347         }
348
349         if (!IN6_IS_ADDR_MULTICAST((struct in6_addr *)dest_addr) && iov[IOV_NESTED].iov_len == 0 &&
350                 (opts[-4] == DHCPV6_MSG_REQUEST || opts[-4] == DHCPV6_MSG_RENEW ||
351                  opts[-4] == DHCPV6_MSG_RELEASE || opts[-4] == DHCPV6_MSG_DECLINE)) {
352                 iov[IOV_STAT].iov_base = &stat;
353                 iov[IOV_STAT].iov_len = sizeof(stat);
354
355                 for (ssize_t i = IOV_STAT + 1; i < IOV_TOTAL; ++i)
356                         iov[i].iov_len = 0;
357
358                 odhcpd_send(iface->dhcpv6_event.uloop.fd, addr, iov, ARRAY_SIZE(iov), iface);
359                 return;
360         }
361
362         if (opts[-4] != DHCPV6_MSG_INFORMATION_REQUEST) {
363                 ssize_t ialen = dhcpv6_handle_ia(pdbuf, sizeof(pdbuf), iface, addr, &opts[-4], opts_end);
364                 iov[IOV_PDBUF].iov_len = ialen;
365                 if (ialen < 0 || (ialen == 0 && (opts[-4] == DHCPV6_MSG_REBIND || opts[-4] == DHCPV6_MSG_CONFIRM)))
366                         return;
367         }
368
369         if (iov[IOV_NESTED].iov_len > 0) // Update length
370                 update_nested_message(data, len, iov[IOV_DEST].iov_len + iov[IOV_MAXRT].iov_len +
371                                 iov[IOV_DNS].iov_len + iov[IOV_DNS_ADDR].iov_len +
372                                 iov[IOV_SEARCH].iov_len + iov[IOV_SEARCH_DOMAIN].iov_len +
373                                 iov[IOV_PDBUF].iov_len + iov[IOV_CERID].iov_len +
374                                 iov[IOV_DHCPV6_RAW].iov_len - (4 + opts_end - opts));
375
376         odhcpd_send(iface->dhcpv6_event.uloop.fd, addr, iov, ARRAY_SIZE(iov), iface);
377 }
378
379
380 // Central DHCPv6-relay handler
381 static void handle_dhcpv6(void *addr, void *data, size_t len,
382                 struct interface *iface, void *dest_addr)
383 {
384         if (iface->dhcpv6 == RELAYD_SERVER) {
385                 handle_client_request(addr, data, len, iface, dest_addr);
386         } else if (iface->dhcpv6 == RELAYD_RELAY) {
387                 if (iface->master)
388                         relay_server_response(data, len);
389                 else
390                         relay_client_request(addr, data, len, iface);
391         }
392 }
393
394
395 // Relay server response (regular relay server handling)
396 static void relay_server_response(uint8_t *data, size_t len)
397 {
398         // Information we need to gather
399         uint8_t *payload_data = NULL;
400         size_t payload_len = 0;
401         int32_t ifaceidx = 0;
402         struct sockaddr_in6 target = {AF_INET6, htons(DHCPV6_CLIENT_PORT),
403                 0, IN6ADDR_ANY_INIT, 0};
404
405         syslog(LOG_NOTICE, "Got a DHCPv6-reply");
406
407         int otype, olen;
408         uint8_t *odata, *end = data + len;
409
410         // Relay DHCPv6 reply from server to client
411         struct dhcpv6_relay_header *h = (void*)data;
412         if (len < sizeof(*h) || h->msg_type != DHCPV6_MSG_RELAY_REPL)
413                 return;
414
415         memcpy(&target.sin6_addr, &h->peer_address,
416                         sizeof(struct in6_addr));
417
418         // Go through options and find what we need
419         dhcpv6_for_each_option(h->options, end, otype, olen, odata) {
420                 if (otype == DHCPV6_OPT_INTERFACE_ID
421                                 && olen == sizeof(ifaceidx)) {
422                         memcpy(&ifaceidx, odata, sizeof(ifaceidx));
423                 } else if (otype == DHCPV6_OPT_RELAY_MSG) {
424                         payload_data = odata;
425                         payload_len = olen;
426                 }
427         }
428
429         // Invalid interface-id or basic payload
430         struct interface *iface = odhcpd_get_interface_by_index(ifaceidx);
431         if (!iface || iface->master || !payload_data || payload_len < 4)
432                 return;
433
434         bool is_authenticated = false;
435         struct in6_addr *dns_ptr = NULL;
436         size_t dns_count = 0;
437
438         // If the payload is relay-reply we have to send to the server port
439         if (payload_data[0] == DHCPV6_MSG_RELAY_REPL) {
440                 target.sin6_port = htons(DHCPV6_SERVER_PORT);
441         } else { // Go through the payload data
442                 struct dhcpv6_client_header *h = (void*)payload_data;
443                 end = payload_data + payload_len;
444
445                 dhcpv6_for_each_option(&h[1], end, otype, olen, odata) {
446                         if (otype == DHCPV6_OPT_DNS_SERVERS && olen >= 16) {
447                                 dns_ptr = (struct in6_addr*)odata;
448                                 dns_count = olen / 16;
449                         } else if (otype == DHCPV6_OPT_AUTH) {
450                                 is_authenticated = true;
451                         }
452                 }
453         }
454
455         // Rewrite DNS servers if requested
456         if (iface->always_rewrite_dns && dns_ptr && dns_count > 0) {
457                 if (is_authenticated)
458                         return; // Impossible to rewrite
459
460                 const struct in6_addr *rewrite = iface->dns;
461                 struct in6_addr addr;
462                 size_t rewrite_cnt = iface->dns_cnt;
463
464                 if (rewrite_cnt == 0) {
465                         if (odhcpd_get_interface_dns_addr(iface, &addr))
466                                 return; // Unable to get interface address
467
468                         rewrite = &addr;
469                         rewrite_cnt = 1;
470                 }
471
472                 // Copy over any other addresses
473                 for (size_t i = 0; i < dns_count; ++i) {
474                         size_t j = (i < rewrite_cnt) ? i : rewrite_cnt - 1;
475                         memcpy(&dns_ptr[i], &rewrite[j], sizeof(*rewrite));
476                 }
477         }
478
479         struct iovec iov = {payload_data, payload_len};
480         odhcpd_send(iface->dhcpv6_event.uloop.fd, &target, &iov, 1, iface);
481 }
482
483 static struct odhcpd_ipaddr *relay_link_address(struct interface *iface)
484 {
485         struct odhcpd_ipaddr *addr = NULL;
486         time_t now = odhcpd_time();
487
488         for (size_t i = 0; i < iface->ia_addr_len; i++) {
489                 if (iface->ia_addr[i].valid <= (uint32_t)now)
490                         continue;
491
492                 if (iface->ia_addr[i].preferred > (uint32_t)now) {
493                         addr = &iface->ia_addr[i];
494                         break;
495                 }
496
497                 if (!addr || (iface->ia_addr[i].valid > addr->valid))
498                         addr = &iface->ia_addr[i];
499         }
500
501         return addr;
502 }
503
504 // Relay client request (regular DHCPv6-relay)
505 static void relay_client_request(struct sockaddr_in6 *source,
506                 const void *data, size_t len, struct interface *iface)
507 {
508         struct interface *master = odhcpd_get_master_interface();
509         const struct dhcpv6_relay_header *h = data;
510         if (!master || master->dhcpv6 != RELAYD_RELAY ||
511                         h->msg_type == DHCPV6_MSG_RELAY_REPL ||
512                         h->msg_type == DHCPV6_MSG_RECONFIGURE ||
513                         h->msg_type == DHCPV6_MSG_REPLY ||
514                         h->msg_type == DHCPV6_MSG_ADVERTISE)
515                 return; // Invalid message types for client
516
517         syslog(LOG_NOTICE, "Got a DHCPv6-request");
518
519         // Construct our forwarding envelope
520         struct dhcpv6_relay_forward_envelope hdr = {
521                 .msg_type = DHCPV6_MSG_RELAY_FORW,
522                 .hop_count = 0,
523                 .interface_id_type = htons(DHCPV6_OPT_INTERFACE_ID),
524                 .interface_id_len = htons(sizeof(uint32_t)),
525                 .relay_message_type = htons(DHCPV6_OPT_RELAY_MSG),
526                 .relay_message_len = htons(len),
527         };
528
529         if (h->msg_type == DHCPV6_MSG_RELAY_FORW) { // handle relay-forward
530                 if (h->hop_count >= DHCPV6_HOP_COUNT_LIMIT)
531                         return; // Invalid hop count
532                 else
533                         hdr.hop_count = h->hop_count + 1;
534         }
535
536         // use memcpy here as the destination fields are unaligned
537         uint32_t ifindex = iface->ifindex;
538         memcpy(&hdr.peer_address, &source->sin6_addr, sizeof(struct in6_addr));
539         memcpy(&hdr.interface_id_data, &ifindex, sizeof(ifindex));
540
541         // Detect public IP of slave interface to use as link-address
542         struct odhcpd_ipaddr *ip = relay_link_address(iface);
543         if (!ip) {
544                 // No suitable address! Is the slave not configured yet?
545                 // Detect public IP of master interface and use it instead
546                 // This is WRONG and probably violates the RFC. However
547                 // otherwise we have a hen and egg problem because the
548                 // slave-interface cannot be auto-configured.
549                 ip = relay_link_address(master);
550                 if (!ip)
551                         return; // Could not obtain a suitable address
552         }
553
554         memcpy(&hdr.link_address, &ip->addr.in6, sizeof(hdr.link_address));
555
556         struct sockaddr_in6 dhcpv6_servers = {AF_INET6,
557                         htons(DHCPV6_SERVER_PORT), 0, ALL_DHCPV6_SERVERS, 0};
558         struct iovec iov[2] = {{&hdr, sizeof(hdr)}, {(void*)data, len}};
559         odhcpd_send(master->dhcpv6_event.uloop.fd, &dhcpv6_servers, iov, 2, master);
560 }