1 files changed, 5 insertions, 0 deletions
diff --git a/winsup/cygwin/net.cc b/winsup/cygwin/net.cc
index 053c66718..e81de79c1 100644
--- a/winsup/cygwin/net.cc
+++ b/winsup/cygwin/net.cc
@@ -636,6 +636,11 @@ fdsock (cygheap_fdmanip& fd, const device *dev, SOCKET soc)
 	system_printf ("getsockopt(SO_SNDBUF) failed, %u", WSAGetLastError ());
     }
 
+  /* A unique ID is necessary to recognize fhandler entries which are
+     duplicated by dup(2) or fork(2).  This is used in BSD flock calls
+     to identify the descriptor. */
+  ((fhandler_socket *) fd)->set_unique_id ();
+
   return true;
 }