Set SO_REUSEPORT on the multicast sockets.

On Linux this doesn't make any difference, but on macOS this is required
if any other process has already opened an mDNS multicast socket locally,
otherwise bind() will fail.

diff --git a/src/discovery.c b/src/discovery.c
index eb29c735f63e4c3e06a3c9f840243fd10b5183d0..439bcbef479a1e6053ab2109bee4f9650098934f 100644 (file)
--- a/src/discovery.c
+++ b/src/discovery.c
@@ -669,28 +669,48 @@ bool discovery_start(meshlink_handle_t *mesh) {
        static const uint8_t ttl8 = 255;
 
        int fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+
+       if(fd == -1) {
+               logger(mesh, MESHLINK_ERROR, "Error creating IPv4 socket: %s", strerror(errno));
+       }
+
        sockaddr_t sa4 = {
                .in.sin_family = AF_INET,
                .in.sin_port = ntohs(5353),
        };
        setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
+       setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one));
        setsockopt(fd, IPPROTO_IP, IP_MULTICAST_LOOP, &one8, sizeof(one8));
        setsockopt(fd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl8, sizeof(ttl8));
-       bind(fd, &sa4.sa, SALEN(sa4.sa));
-       io_add(&mesh->loop, &mesh->discovery.sockets[0], mdns_io_handler, &mesh->discovery.sockets[0], fd, IO_READ);
+
+       if(bind(fd, &sa4.sa, SALEN(sa4.sa)) == -1) {
+               logger(mesh, MESHLINK_ERROR, "Error binding to IPv4 multicast socket: %s", strerror(errno));
+       } else {
+               io_add(&mesh->loop, &mesh->discovery.sockets[0], mdns_io_handler, &mesh->discovery.sockets[0], fd, IO_READ);
+       }
 
        sockaddr_t sa6 = {
                .in6.sin6_family = AF_INET6,
                .in6.sin6_port = ntohs(5353),
        };
        fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);
+
+       if(fd == -1) {
+               logger(mesh, MESHLINK_ERROR, "Error creating IPv6 socket: %s", strerror(errno));
+       }
+
        setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
+       setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one));
        setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one));
        setsockopt(fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &one, sizeof(one));
        setsockopt(fd, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &ttl, sizeof(ttl));
        setsockopt(fd, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &ttl, sizeof(ttl));
-       bind(fd, &sa6.sa, SALEN(sa6.sa));
-       io_add(&mesh->loop, &mesh->discovery.sockets[1], mdns_io_handler, &mesh->discovery.sockets[1], fd, IO_READ);
+
+       if(bind(fd, &sa6.sa, SALEN(sa6.sa)) == -1) {
+               logger(mesh, MESHLINK_ERROR, "Error binding to IPv4 multicast socket: %s", strerror(errno));
+       } else {
+               io_add(&mesh->loop, &mesh->discovery.sockets[1], mdns_io_handler, &mesh->discovery.sockets[1], fd, IO_READ);
+       }
 
 #if defined(__linux)
        int sock = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE);