2 * Copyright (C) 2014 John Crispin <blogic@openwrt.org>
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU Lesser General Public License version 2.1
6 * as published by the Free Software Foundation
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.
14 #include <sys/types.h>
22 #include <sys/types.h>
23 #include <sys/socket.h>
24 #include <netinet/in.h>
25 #include <arpa/inet.h>
26 #include <arpa/nameser.h>
31 #include <libubox/uloop.h>
32 #include <libubox/usock.h>
33 #include <libubox/utils.h>
40 #include "interface.h"
42 static char name_buffer[MAX_NAME_LEN + 1];
43 static char dns_buffer[MAX_NAME_LEN];
44 static struct blob_buf ans_buf;
47 dns_type_string(uint16_t type)
54 { TYPE_AAAA, "AAAA" },
62 for (i = 0; i < ARRAY_SIZE(type_str); i++) {
63 if (type == type_str[i].type)
64 return type_str[i].str;
71 dns_send_question(struct interface *iface, struct sockaddr *to,
72 const char *question, int type, int multicast)
74 static struct dns_header h;
75 static struct dns_question q;
76 static struct iovec iov[] = {
82 .iov_base = dns_buffer,
91 h.questions = cpu_to_be16(1);
92 q.class = cpu_to_be16((multicast ? 0 : CLASS_UNICAST) | 1);
93 q.type = cpu_to_be16(type);
95 len = dn_comp(question, (void *) dns_buffer, sizeof(dns_buffer), NULL, NULL);
101 DBG(1, "Q <- %s %s\n", dns_type_string(type), question);
102 if (interface_send_packet(iface, to, iov, ARRAY_SIZE(iov)) < 0)
103 perror("failed to send question");
115 static int dns_answer_cnt;
118 dns_init_answer(void)
121 blob_buf_init(&ans_buf, 0);
125 dns_add_answer(int type, const uint8_t *rdata, uint16_t rdlength, int ttl)
127 struct blob_attr *attr;
128 struct dns_answer *a;
130 attr = blob_new(&ans_buf, 0, sizeof(*a) + rdlength);
132 a->type = cpu_to_be16(type);
133 a->class = cpu_to_be16(1);
134 a->ttl = cpu_to_be32(ttl);
135 a->rdlength = cpu_to_be16(rdlength);
136 memcpy(a + 1, rdata, rdlength);
142 dns_send_answer(struct interface *iface, struct sockaddr *to, const char *answer)
145 struct blob_attr *attr;
146 struct dns_header h = { 0 };
154 h.answers = cpu_to_be16(dns_answer_cnt);
155 h.flags = cpu_to_be16(0x8400);
157 iov = alloca(sizeof(struct iovec) * ((dns_answer_cnt * 2) + 1));
159 iov[n_iov].iov_base = &h;
160 iov[n_iov].iov_len = sizeof(struct dns_header);
163 answer_len = dn_comp(answer, buffer, sizeof(buffer), NULL, NULL);
167 blob_for_each_attr(attr, ans_buf.head, rem) {
168 struct dns_answer *a = blob_data(attr);
170 iov[n_iov].iov_base = buffer;
171 iov[n_iov].iov_len = answer_len;
174 iov[n_iov].iov_base = blob_data(attr);
175 iov[n_iov].iov_len = blob_len(attr);
178 DBG(1, "A <- %s %s\n", dns_type_string(be16_to_cpu(a->type)), answer);
181 if (interface_send_packet(iface, to, iov, n_iov) < 0)
182 perror("failed to send answer");
186 dns_reply_a(struct interface *iface, struct sockaddr *to, int ttl)
188 struct ifaddrs *ifap, *ifa;
189 struct sockaddr_in *sa;
190 struct sockaddr_in6 *sa6;
195 for (ifa = ifap; ifa; ifa = ifa->ifa_next) {
196 if (strcmp(ifa->ifa_name, iface->name))
198 if (ifa->ifa_addr->sa_family == AF_INET) {
199 sa = (struct sockaddr_in *) ifa->ifa_addr;
200 dns_add_answer(TYPE_A, (uint8_t *) &sa->sin_addr, 4, ttl);
202 if (ifa->ifa_addr->sa_family == AF_INET6) {
203 sa6 = (struct sockaddr_in6 *) ifa->ifa_addr;
204 dns_add_answer(TYPE_AAAA, (uint8_t *) &sa6->sin6_addr, 16, ttl);
207 dns_send_answer(iface, to, mdns_hostname_local);
213 scan_name(const uint8_t *buffer, int len)
217 while (len && (*buffer != '\0')) {
220 if (IS_COMPRESSED(l))
223 if (l + 1 > len) return -1;
229 if (!len || !offset || (*buffer != '\0'))
235 static struct dns_header*
236 dns_consume_header(uint8_t **data, int *len)
238 struct dns_header *h = (struct dns_header *) *data;
240 if (*len < sizeof(struct dns_header))
243 h->id = be16_to_cpu(h->id);
244 h->flags = be16_to_cpu(h->flags);
245 h->questions = be16_to_cpu(h->questions);
246 h->answers = be16_to_cpu(h->answers);
247 h->authority = be16_to_cpu(h->authority);
248 h->additional = be16_to_cpu(h->additional);
250 *len -= sizeof(struct dns_header);
251 *data += sizeof(struct dns_header);
256 static struct dns_question*
257 dns_consume_question(uint8_t **data, int *len)
259 struct dns_question *q = (struct dns_question *) *data;
261 if (*len < sizeof(struct dns_question))
264 q->type = be16_to_cpu(q->type);
265 q->class = be16_to_cpu(q->class);
267 *len -= sizeof(struct dns_question);
268 *data += sizeof(struct dns_question);
273 static struct dns_answer*
274 dns_consume_answer(uint8_t **data, int *len)
276 struct dns_answer *a = (struct dns_answer *) *data;
278 if (*len < sizeof(struct dns_answer))
281 a->type = be16_to_cpu(a->type);
282 a->class = be16_to_cpu(a->class);
283 a->ttl = be32_to_cpu(a->ttl);
284 a->rdlength = be16_to_cpu(a->rdlength);
286 *len -= sizeof(struct dns_answer);
287 *data += sizeof(struct dns_answer);
293 dns_consume_name(const uint8_t *base, int blen, uint8_t **data, int *len)
295 int nlen = scan_name(*data, *len);
300 if (dn_expand(base, base + blen, *data, name_buffer, MAX_NAME_LEN) < 0) {
301 perror("dns_consume_name/dn_expand");
311 static int parse_answer(struct interface *iface, struct sockaddr *from,
312 uint8_t *buffer, int len, uint8_t **b, int *rlen,
315 char *name = dns_consume_name(buffer, len, b, rlen);
316 struct dns_answer *a;
319 if (!name || *rlen < 0) {
320 fprintf(stderr, "dropping: bad question\n");
324 a = dns_consume_answer(b, rlen);
326 fprintf(stderr, "dropping: bad question\n");
330 if ((a->class & ~CLASS_FLUSH) != CLASS_IN)
334 if (a->rdlength > *rlen) {
335 fprintf(stderr, "dropping: bad question\n");
339 *rlen -= a->rdlength;
343 cache_answer(iface, from, buffer, len, name, a, rdata, a->class & CLASS_FLUSH);
349 parse_question(struct interface *iface, struct sockaddr *from, char *name, struct dns_question *q)
351 struct sockaddr *to = NULL;
354 /* TODO: Multicast if more than one quarter of TTL has passed */
355 if (q->class & CLASS_UNICAST) {
357 if (iface->multicast)
361 DBG(1, "Q -> %s %s\n", dns_type_string(q->type), name);
365 if (!strcmp(name, mdns_hostname_local)) {
366 dns_reply_a(iface, to, announce_ttl);
367 service_reply(iface, to, NULL, NULL, announce_ttl);
372 if (!strcmp(name, C_DNS_SD)) {
373 dns_reply_a(iface, to, announce_ttl);
374 service_announce_services(iface, to, announce_ttl);
376 if (name[0] == '_') {
377 service_reply(iface, to, NULL, name, announce_ttl);
379 /* First dot separates instance name from the rest */
380 char *dot = strchr(name, '.');
384 service_reply(iface, to, name, dot + 1, announce_ttl);
393 host = strstr(name, ".local");
396 if (!strcmp(umdns_host_label, name))
397 dns_reply_a(iface, to, announce_ttl);
403 dns_handle_packet(struct interface *iface, struct sockaddr *from, uint16_t port, uint8_t *buffer, int len)
405 struct dns_header *h;
409 h = dns_consume_header(&b, &rlen);
411 fprintf(stderr, "dropping: bad header\n");
415 if (h->questions && !iface->multicast && port != MCAST_PORT)
416 /* silently drop unicast questions that dont originate from port 5353 */
419 while (h->questions-- > 0) {
420 char *name = dns_consume_name(buffer, len, &b, &rlen);
421 struct dns_question *q;
423 if (!name || rlen < 0) {
424 fprintf(stderr, "dropping: bad name\n");
428 q = dns_consume_question(&b, &rlen);
430 fprintf(stderr, "dropping: bad question\n");
434 if (!(h->flags & FLAG_RESPONSE))
435 parse_question(iface, from, name, q);
438 if (!(h->flags & FLAG_RESPONSE))
441 while (h->answers-- > 0)
442 if (parse_answer(iface, from, buffer, len, &b, &rlen, 1))
445 while (h->authority-- > 0)
446 if (parse_answer(iface, from, buffer, len, &b, &rlen, 1))
449 while (h->additional-- > 0)
450 if (parse_answer(iface, from, buffer, len, &b, &rlen, 1))