+#ifndef MSG_NOSIGNAL
+#define MSG_NOSIGNAL 0
+#endif
+
+#ifndef IPV6_ADD_MEMBERSHIP
+#define IPV6_ADD_MEMBERSHIP IPV6_JOIN_GROUP
+#endif
+
+#ifndef IPV6_DROP_MEMBERSHIP
+#define IPV6_DROP_MEMBERSHIP IPV6_LEAVE_GROUP
+#endif
+
+static const sockaddr_t mdns_address_ipv4 = {
+ .in.sin_family = AF_INET,
+ .in.sin_addr.s_addr = 0xfb0000e0,
+ .in.sin_port = 0xe914,
+};
+
+static const sockaddr_t mdns_address_ipv6 = {
+ .in6.sin6_family = AF_INET6,
+ .in6.sin6_addr.s6_addr[0x0] = 0xfd,
+ .in6.sin6_addr.s6_addr[0x1] = 0x02,
+ .in6.sin6_addr.s6_addr[0xf] = 0xfb,
+ .in6.sin6_port = 0xe914,
+};
+
+typedef struct discovery_address {
+ int index;
+ bool up;
+ sockaddr_t address;
+} discovery_address_t;
+
+static int iface_compare(const void *va, const void *vb) {
+ const int *a = va;
+ const int *b = vb;
+ return *a - *b;
+}
+
+static int address_compare(const void *va, const void *vb) {
+ const discovery_address_t *a = va;
+ const discovery_address_t *b = vb;
+
+ if(a->index != b->index) {
+ return a->index - b->index;
+ }
+
+ return sockaddrcmp_noport(&a->address, &b->address);
+}
+
+static void send_mdns_packet_ipv4(meshlink_handle_t *mesh, int fd, int index, const sockaddr_t *src, const sockaddr_t *dest, void *data, size_t len) {
+#ifdef IP_PKTINFO
+ struct iovec iov = {
+ .iov_base = data,
+ .iov_len = len,
+ };
+
+ struct in_pktinfo pkti = {
+ .ipi_ifindex = index,
+ .ipi_addr = src->in.sin_addr,
+ };
+
+ union {
+ char buf[CMSG_SPACE(sizeof(pkti))];
+ struct cmsghdr align;
+ } u;
+
+ struct msghdr msg = {
+ .msg_name = (struct sockaddr *) &dest->sa,
+ .msg_namelen = SALEN(dest->sa),
+ .msg_iov = &iov,
+ .msg_iovlen = 1,
+ .msg_control = u.buf,
+ .msg_controllen = sizeof(u.buf),
+ };
+
+
+ struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
+ cmsg->cmsg_level = IPPROTO_IP;
+ cmsg->cmsg_type = IP_PKTINFO;
+ cmsg->cmsg_len = CMSG_LEN(sizeof(pkti));
+ memcpy(CMSG_DATA(cmsg), &pkti, sizeof(pkti));
+
+ // Send the packet
+ ssize_t result = sendmsg(fd, &msg, MSG_DONTWAIT | MSG_NOSIGNAL);
+#else
+ (void)index;
+ (void)src;
+
+ // Send the packet
+ ssize_t result = sendto(fd, data, len, MSG_DONTWAIT | MSG_NOSIGNAL, &dest->sa, SALEN(dest->sa));
+#endif
+
+ if(result <= 0) {
+ logger(mesh, MESHLINK_ERROR, "Error sending multicast packet: %s", strerror(errno));