From 3eab592c223e145cd32f8bf41e1b8a4ca26c4961 Mon Sep 17 00:00:00 2001
From: Ken Brown <kbrown@cornell.edu>
Date: Sun, 4 Oct 2020 10:38:29 -0400
Subject: [PATCH] Cygwin: AF_UNIX: sendmsg: fix return value

On a successful write, the return value is now the number of bytes of
user data written, not the total number of bytes written.
---
 winsup/cygwin/fhandler_socket_unix.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/winsup/cygwin/fhandler_socket_unix.cc b/winsup/cygwin/fhandler_socket_unix.cc
index 2816b0e31..30009500c 100644
--- a/winsup/cygwin/fhandler_socket_unix.cc
+++ b/winsup/cygwin/fhandler_socket_unix.cc
@@ -2090,7 +2090,7 @@ wait:
 	  if (io.Information == 0)
 	    set_errno (EAGAIN);
 	  else
-	    ret = io.Information;
+	    ret = io.Information - AF_UNIX_PKT_OFFSETOF_DATA (packet);
 	}
       else if (STATUS_PIPE_IS_CLOSED (status))
 	{