Add accept4() system call.

The accept4() function, compared to accept(), allows setting the new file
descriptor atomically close-on-exec and explicitly controlling the
non-blocking status on the new socket. (Note that the latter point means
that accept() is not equivalent to any form of accept4().)

The linuxulator's accept4 implementation leaves a race window where the new
file descriptor is not close-on-exec because it calls sys_accept(). This
implementation leaves no such race window (by using falloc() flags). The
linuxulator could be fixed and simplified by using the new code.

Like accept(), accept4() is async-signal-safe, a cancellation point and
permitted in capability mode.

1 files changed, 5 insertions, 0 deletions

diff --git a/lib/libthr/pthread.map b/lib/libthr/pthread.map
index 355edea..bbbd930e 100644
--- a/lib/libthr/pthread.map
+++ b/lib/libthr/pthread.map
@@ -181,6 +181,7 @@ FBSDprivate_1.0 {
 	___wait;
 	___waitpid;
 	__accept;
+	__accept4;
 	__aio_suspend;
 	__close;
 	__connect;
@@ -408,3 +409,7 @@ FBSD_1.2 {
 	setcontext;
 	swapcontext;
 };
+
+FBSD_1.3 {
+	accept4;
+};