+
+static int parse_answer(struct interface *iface, struct sockaddr *from,
+ uint8_t *buffer, int len, uint8_t **b, int *rlen,
+ int cache)
+{
+ char *name = dns_consume_name(buffer, len, b, rlen);
+ struct dns_answer *a;
+ uint8_t *rdata;
+
+ if (!name) {
+ fprintf(stderr, "dropping: bad question\n");
+ return -1;
+ }
+
+ a = dns_consume_answer(b, rlen);
+ if (!a) {
+ fprintf(stderr, "dropping: bad question\n");
+ return -1;
+ }
+
+ if ((a->class & ~CLASS_FLUSH) != CLASS_IN)
+ return -1;
+
+ rdata = *b;
+ if (a->rdlength > *rlen) {
+ fprintf(stderr, "dropping: bad question\n");
+ return -1;
+ }
+
+ *rlen -= a->rdlength;
+ *b += a->rdlength;
+
+ if (cache)
+ cache_answer(iface, from, buffer, len, name, a, rdata, a->class & CLASS_FLUSH);
+
+ return 0;
+}
+
+static void
+parse_question(struct interface *iface, struct sockaddr *from, char *name, struct dns_question *q)
+{
+ struct sockaddr *to = NULL;
+ char *host;
+
+ /* TODO: Multicast if more than one quarter of TTL has passed */
+ if (q->class & CLASS_UNICAST) {
+ to = from;
+ if (iface->multicast)
+ iface = iface->peer;
+ }
+
+ DBG(1, "Q -> %s %s\n", dns_type_string(q->type), name);
+
+ switch (q->type) {
+ case TYPE_ANY:
+ if (!strcmp(name, mdns_hostname_local)) {
+ dns_reply_a(iface, to, announce_ttl);
+ service_reply(iface, to, NULL, NULL, announce_ttl);
+ }
+ break;
+
+ case TYPE_PTR:
+ if (!strcmp(name, C_DNS_SD)) {
+ dns_reply_a(iface, to, announce_ttl);
+ service_announce_services(iface, to, announce_ttl);
+ } else {
+ if (name[0] == '_') {
+ service_reply(iface, to, NULL, name, announce_ttl);
+ } else {
+ /* First dot separates instance name from the rest */
+ char *dot = strchr(name, '.');
+
+ if (dot) {
+ *dot = '\0';
+ service_reply(iface, to, name, dot + 1, announce_ttl);
+ *dot = '.';
+ }
+ }
+ }
+ break;
+
+ case TYPE_AAAA:
+ case TYPE_A:
+ host = strstr(name, ".local");
+ if (host)
+ *host = '\0';
+ if (!strcmp(umdns_host_label, name))
+ dns_reply_a(iface, to, announce_ttl);
+ break;
+ };
+}
+
+void
+dns_handle_packet(struct interface *iface, struct sockaddr *from, uint16_t port, uint8_t *buffer, int len)
+{
+ struct dns_header *h;
+ uint8_t *b = buffer;
+ int rlen = len;
+
+ h = dns_consume_header(&b, &rlen);
+ if (!h) {
+ fprintf(stderr, "dropping: bad header\n");
+ return;
+ }
+
+ if (h->questions && !iface->multicast && port != MCAST_PORT)
+ /* silently drop unicast questions that dont originate from port 5353 */
+ return;
+
+ while (h->questions-- > 0) {
+ char *name = dns_consume_name(buffer, len, &b, &rlen);
+ struct dns_question *q;
+
+ if (!name) {
+ fprintf(stderr, "dropping: bad name\n");
+ return;
+ }
+
+ q = dns_consume_question(&b, &rlen);
+ if (!q) {
+ fprintf(stderr, "dropping: bad question\n");
+ return;
+ }
+
+ if (!(h->flags & FLAG_RESPONSE))
+ parse_question(iface, from, name, q);
+ }
+
+ if (!(h->flags & FLAG_RESPONSE))
+ return;
+
+ while (h->answers-- > 0)
+ if (parse_answer(iface, from, buffer, len, &b, &rlen, 1))
+ return;
+
+ while (h->authority-- > 0)
+ if (parse_answer(iface, from, buffer, len, &b, &rlen, 1))
+ return;
+
+ while (h->additional-- > 0)
+ if (parse_answer(iface, from, buffer, len, &b, &rlen, 1))
+ return;
+
+}