Linux accept4() support

auto/os/features

diff --git a/auto/os/features b/auto/os/features
index ecd8e7f..c0fd6dd 100644
--- a/auto/os/features
+++ b/auto/os/features
@@ -305,6 +305,15 @@
 . auto/feature
 
 
+ngx_feature="accept4()"
+ngx_feature_name="NGX_HAVE_ACCEPT4"
+ngx_feature_run=no
+ngx_feature_incs="#include <sys/socket.h>"
+ngx_feature_path=
+ngx_feature_libs=
+ngx_feature_test="accept4(0, NULL, NULL, SOCK_NONBLOCK)"
+. auto/feature
+
 if [ $NGX_FILE_AIO = YES ]; then
 
     ngx_feature="kqueue AIO support"

src/event/ngx_event_accept.c

diff --git a/src/event/ngx_event_accept.c b/src/event/ngx_event_accept.c
index ed5762e..67751fa 100644
--- a/src/event/ngx_event_accept.c
+++ b/src/event/ngx_event_accept.c
@@ -46,7 +46,11 @@
     do {
         socklen = NGX_SOCKADDRLEN;
 
+#if (NGX_HAVE_ACCEPT4)
+        s = accept4(lc->fd, (struct sockaddr *) sa, &socklen, SOCK_NONBLOCK);
+#else
         s = accept(lc->fd, (struct sockaddr *) sa, &socklen);
+#endif
 
         if (s == -1) {
             err = ngx_socket_errno;

src/os/unix/ngx_posix_init.c

diff --git a/src/os/unix/ngx_posix_init.c b/src/os/unix/ngx_posix_init.c
index f216144..2357ab3 100644
--- a/src/os/unix/ngx_posix_init.c
+++ b/src/os/unix/ngx_posix_init.c
@@ -60,7 +60,7 @@
 
     ngx_max_sockets = (ngx_int_t) rlmt.rlim_cur;
 
-#if (NGX_HAVE_INHERITED_NONBLOCK)
+#if (NGX_HAVE_INHERITED_NONBLOCK || NGX_HAVE_ACCEPT4)
     ngx_inherited_nonblocking = 1;
 #else
     ngx_inherited_nonblocking = 0;