Switch to more consistently setting sockets non-blocking.

incoming.c

@@ -1,3 +1,5 @@
+#define _GNU_SOURCE
+
 #include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -26,7 +28,7 @@ static void incoming_handler(struct peer *peer) {
 	struct sockaddr peer_addr, local_addr;
 	socklen_t peer_addrlen = sizeof(peer_addr), local_addrlen = sizeof(local_addr);
 
-	int fd = accept(incoming->peer.fd, &peer_addr, &peer_addrlen);
+	int fd = accept4(incoming->peer.fd, &peer_addr, &peer_addrlen, SOCK_NONBLOCK);
 	if (fd == -1) {
 		fprintf(stderr, "I %s: Failed to accept new connection on %s/%s: %s\n", incoming->id, incoming->node, incoming->service, strerror(errno));
 		return;

send.c

@@ -4,7 +4,6 @@
 #include <strings.h>
 #include <stdio.h>
 #include <unistd.h>
-#include <fcntl.h>
 #include <signal.h>
 
 #include "common.h"
@@ -98,11 +97,6 @@ struct serializer *send_get_serializer(char *name) {
 }
 
 void send_add(int fd, struct serializer *serializer) {
-	int flags = fcntl(fd, F_GETFL, 0);
-	assert(flags >= 0);
-	flags |= O_NONBLOCK;
-	assert(fcntl(fd, F_SETFL, flags) == 0);
-
 	if (!send_hello(fd, serializer)) {
 		fprintf(stderr, "S xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx: Failed to write hello\n");
 		return;