Enable SO_REUSE{ADDR,PORT} for TCP/IP server sockets (#460)

Otherwise `renderd` processes configured to use TCP/IP server sockets may need to wait until the address and/or port are released before restarting under certain circumstances (especially an ungraceful termination).

src/renderd.c

@@ -494,6 +494,8 @@ int server_socket_init(renderd_config *sConfig)
 	int fd;
 
 	if (sConfig->ipport > 0) {
+		const int enable = 1;
+
 		g_logger(G_LOG_LEVEL_INFO, "Initialising TCP/IP server socket on %s:%i",
 			 sConfig->iphostname, sConfig->ipport);
 		fd = socket(PF_INET6, SOCK_STREAM, 0);
@@ -503,6 +505,18 @@ int server_socket_init(renderd_config *sConfig)
 			exit(2);
 		}
 
+		if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(enable)) < 0) {
+			g_logger(G_LOG_LEVEL_CRITICAL, "setsockopt SO_REUSEADDR failed for: %s:%i",
+				 sConfig->iphostname, sConfig->ipport);
+			exit(3);
+		}
+
+		if (setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &enable, sizeof(enable)) < 0) {
+			g_logger(G_LOG_LEVEL_CRITICAL, "setsockopt SO_REUSEPORT failed for: %s:%i",
+				 sConfig->iphostname, sConfig->ipport);
+			exit(3);
+		}
+
 		bzero(&addrI, sizeof(addrI));
 		addrI.sin6_family = AF_INET6;
 		addrI.sin6_addr = in6addr_any;