1 files changed, 10 insertions, 3 deletions

diff --git a/ot_socket.c b/ot_socket.c
index 158459f..47ed26d 100644
--- a/ot_socket.c
+++ b/ot_socket.c
@@ -4,6 +4,7 @@
    $id$ */
 
 /* System */
+#define _GNU_SOURCE /* accept4 on glibc */
 #include <errno.h>
 #include <fcntl.h>
 #include <netinet/in.h>
@@ -170,19 +171,25 @@ int socket_is_connected(int s) {
   return 1;
 }
 
+/* Linux hands over a blocking socket whatever the listening socket was, the
+   BSDs and macOS inherit the listener's flags, so the accepted socket has to
+   be told either way. accept4 carries the flag itself, which saves the two
+   fcntl calls it otherwise takes. Darwin has neither accept4 nor the flag. */
 int socket_accept(int s, ot_ip6 ip, uint16_t *port) {
   struct sockaddr_storage ss;
   socklen_t               len = sizeof(ss);
   int                     fd;
 
   memset(&ss, 0, sizeof(ss));
+#ifdef SOCK_NONBLOCK
+  if ((fd = accept4(s, (struct sockaddr *)&ss, &len, SOCK_NONBLOCK)) == -1)
+    return -1;
+#else
   if ((fd = accept(s, (struct sockaddr *)&ss, &len)) == -1)
     return -1;
-
-  /* Linux hands over a blocking socket whatever the listening socket was, the
-     BSDs and macOS inherit the listener's flags, so say which one we want. */
   if (set_nonblocking(fd) == -1)
     return close_and_fail(fd);
+#endif
 
   ip_from_sockaddr(ip, port, &ss);
   return fd;