[PATCH v2 1/5] Cygwin: AF_LOCAL: allow opening with the O_PATH flag

[Ken Brown]

If that flag is not set, or if an attempt is made to open a different
type of socket, the errno is now EOPNOTSUPP instead of ENXIO.  This is
consistent with POSIX, starting with the 2016 edition.  Earlier
editions were silent on this issue.

Opening is done in a (new) fhandler_socket_local::open method by
calling fhandler_base::open_fs.

Also add a corresponding fhandler_socket_local::close method.
---
 winsup/cygwin/fhandler.h               |  2 ++
 winsup/cygwin/fhandler_socket_local.cc | 20 ++++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index 80a78d14c..c54780ef6 100644
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -834,6 +834,8 @@ class fhandler_socket_local: public fhandler_socket_wsock
   int getsockopt (int level, int optname, const void *optval,
                  __socklen_t *optlen);
 
+  int open (int flags, mode_t mode = 0);
+  int close ();
   int __reg2 fstat (struct stat *buf);
   int __reg2 fstatvfs (struct statvfs *buf);
   int __reg1 fchmod (mode_t newmode);
diff --git a/winsup/cygwin/fhandler_socket_local.cc 
b/winsup/cygwin/fhandler_socket_local.cc
index f88ced22d..e7f4fe603 100644
--- a/winsup/cygwin/fhandler_socket_local.cc
+++ b/winsup/cygwin/fhandler_socket_local.cc
@@ -634,6 +634,26 @@ fhandler_socket_local::dup (fhandler_base *child, int 
flags)
   return fhandler_socket_wsock::dup (child, flags);
 }
 
+int
+fhandler_socket_local::open (int flags, mode_t mode)
+{
+  /* We don't support opening sockets unless O_PATH is specified. */
+  if (flags & O_PATH)
+    return open_fs (flags, mode);
+
+  set_errno (EOPNOTSUPP);
+  return 0;
+}
+
+int
+fhandler_socket_local::close ()
+{
+  if (get_flags () & O_PATH)
+    return fhandler_base::close ();
+  else
+    return fhandler_socket_wsock::close ();
+}
+
 int __reg2
 fhandler_socket_local::fstat (struct stat *buf)
 {
-- 
2.21.0