+static void send_mdns_packet(meshlink_handle_t *mesh, const discovery_address_t *addr) {
+ // Configure the socket to send the packet to the right interface
+ int fd;
+ uint8_t request[1024], response[1024];
+ char *fingerprint = meshlink_get_fingerprint(mesh, (meshlink_node_t *)mesh->self);
+ const char *keys[] = {MESHLINK_MDNS_NAME_KEY, MESHLINK_MDNS_FINGERPRINT_KEY};
+ const char *values[] = {mesh->name, fingerprint};
+ size_t request_size = prepare_request(request, sizeof request, mesh->appname, "tcp");
+ size_t response_size = prepare_response(response, sizeof response, fingerprint, mesh->appname, "tcp", atoi(mesh->myport), 2, keys, values);
+ free(fingerprint);
+
+ switch(addr->address.sa.sa_family) {
+ case AF_INET:
+ fd = mesh->discovery.sockets[0].fd;
+#ifdef IP_MULTICAST_IF
+ {
+ struct ip_mreqn mreq = {
+ .imr_address = addr->address.in.sin_addr,
+ .imr_ifindex = addr->index,
+ };
+
+ if(setsockopt(fd, IPPROTO_IP, IP_MULTICAST_IF, &mreq, sizeof(mreq)) != 0) {
+ logger(mesh, MESHLINK_ERROR, "Could not set outgoing multicast interface on IPv4 socket");
+ return;
+ }
+ }
+
+#endif
+
+ send_mdns_packet_ipv4(mesh, fd, addr->index, &addr->address, &mdns_address_ipv4, request, request_size);
+ send_mdns_packet_ipv4(mesh, fd, addr->index, &addr->address, &mdns_address_ipv4, response, response_size);
+ break;
+
+ case AF_INET6:
+ fd = mesh->discovery.sockets[1].fd;
+#ifdef IPV6_MULTICAST_IF
+
+ if(setsockopt(fd, IPPROTO_IPV6, IPV6_MULTICAST_IF, &addr->index, sizeof(addr->index)) != 0) {
+ logger(mesh, MESHLINK_ERROR, "Could not set outgoing multicast interface on IPv6 socket");
+ return;
+ }
+
+#endif
+
+ send_mdns_packet_ipv6(mesh, fd, addr->index, &addr->address, &mdns_address_ipv6, request, request_size);
+ send_mdns_packet_ipv6(mesh, fd, addr->index, &addr->address, &mdns_address_ipv6, response, response_size);
+ break;
+
+ default:
+ break;
+ }
+}
+
+static void mdns_io_handler(event_loop_t *loop, void *data, int flags) {
+ (void)flags;
+ meshlink_handle_t *mesh = loop->data;
+ io_t *io = data;
+ uint8_t buf[1024];
+ sockaddr_t sa;
+ socklen_t sl = sizeof(sa);
+
+ ssize_t len = recvfrom(io->fd, buf, sizeof(buf), MSG_DONTWAIT, &sa.sa, &sl);
+
+ if(len == -1) {
+ if(!sockwouldblock(errno)) {
+ logger(mesh, MESHLINK_ERROR, "Error reading from mDNS discovery socket: %s", strerror(errno));
+ io_set(loop, io, 0);
+ }
+
+ return;
+ }
+
+ char *name = NULL;
+ uint16_t port = 0;
+ const char *keys[2] = {MESHLINK_MDNS_NAME_KEY, MESHLINK_MDNS_FINGERPRINT_KEY};
+ char *values[2] = {NULL, NULL};
+
+ if(parse_response(buf, len, &name, mesh->appname, "tcp", &port, 2, keys, values)) {
+ node_t *n = (node_t *)meshlink_get_node(mesh, values[0]);
+
+ if(n) {
+ if(n != mesh->self) {
+ logger(mesh, MESHLINK_INFO, "Node %s discovered on the local network.\n", n->name);
+ }
+
+ switch(sa.sa.sa_family) {
+ case AF_INET:
+ sa.in.sin_port = htons(port);
+ break;
+
+ case AF_INET6:
+ sa.in6.sin6_port = htons(port);
+ break;
+
+ default:
+ logger(mesh, MESHLINK_WARNING, "Could not resolve node %s to a known address family type.\n", n->name);
+ sa.sa.sa_family = AF_UNKNOWN;
+ break;
+ }
+
+ if(sa.sa.sa_family != AF_UNKNOWN) {
+ n->catta_address = sa;
+ n->last_connect_try = 0;
+ node_add_recent_address(mesh, n, &sa);
+
+ if(n->connection) {
+ n->connection->last_ping_time = -3600;
+ }
+
+ for list_each(outgoing_t, outgoing, mesh->outgoings) {
+ if(outgoing->node != n) {
+ continue;
+ }
+
+ outgoing->timeout = 0;
+
+ if(outgoing->ev.cb) {
+ timeout_set(&mesh->loop, &outgoing->ev, &(struct timespec) {
+ 0, 0
+ });
+ }
+ }
+ }
+ }
+ } else if(parse_request(buf, len, mesh->appname, "tcp")) {
+ // Send a unicast response back
+ char *fingerprint = meshlink_get_fingerprint(mesh, (meshlink_node_t *)mesh->self);
+ const char *response_values[] = {mesh->name, fingerprint};
+ size_t size = prepare_response(buf, sizeof(buf), fingerprint, mesh->appname, "tcp", atoi(mesh->myport), 2, keys, response_values);
+ sendto(io->fd, buf, size, MSG_DONTWAIT | MSG_NOSIGNAL, &sa.sa, sl);
+ free(fingerprint);
+ }
+
+ free(name);
+
+ for(int i = 0; i < 2; i++) {
+ free(values[i]);
+ }
+}
+
+static void iface_up(meshlink_handle_t *mesh, int index) {
+ int *p = bsearch(&index, mesh->discovery.ifaces, mesh->discovery.iface_count, sizeof(*p), iface_compare);
+
+ if(p) {
+ return;
+ }
+
+ mesh->discovery.ifaces = xrealloc(mesh->discovery.ifaces, ++mesh->discovery.iface_count * sizeof(*p));
+ mesh->discovery.ifaces[mesh->discovery.iface_count - 1] = index;
+ qsort(mesh->discovery.ifaces, mesh->discovery.iface_count, sizeof(*p), iface_compare);
+
+ // Add multicast membership
+ struct ip_mreqn mreq4 = {
+ .imr_multiaddr = mdns_address_ipv4.in.sin_addr,
+ .imr_ifindex = index,
+ };
+ setsockopt(mesh->discovery.sockets[0].fd, IPPROTO_IP, IP_DROP_MEMBERSHIP, &mreq4, sizeof(mreq4));
+ setsockopt(mesh->discovery.sockets[0].fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq4, sizeof(mreq4));
+
+ struct ipv6_mreq mreq6 = {
+ .ipv6mr_multiaddr = mdns_address_ipv6.in6.sin6_addr,
+ .ipv6mr_interface = index,
+ };
+ setsockopt(mesh->discovery.sockets[1].fd, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP, &mreq6, sizeof(mreq6));
+ setsockopt(mesh->discovery.sockets[1].fd, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &mreq6, sizeof(mreq6));
+
+ // Send an announcement for all addresses associated with this interface
+ for(int i = 0; i < mesh->discovery.address_count; i++) {
+ if(mesh->discovery.addresses[i].index == index) {
+ send_mdns_packet(mesh, &mesh->discovery.addresses[i]);
+ }
+ }