[newlib-cygwin] Cygwin: AF_UNIX: allow opening with the O_PATH flag

[Ken Brown <kbrown@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=949fe7bec564f91818bad801bda47a4ddd58fadf

commit 949fe7bec564f91818bad801bda47a4ddd58fadf
Author: Ken Brown <kbrown@cornell.edu>
Date:   Tue Feb 23 11:48:46 2021 -0500

    Cygwin: AF_UNIX: allow opening with the O_PATH flag
    
    This was done for the fhandler_socket_local class in commits
    3a2191653a, 141437d374, and 477121317d, but the fhandler_socket_unix
    class was overlooked.

Diff:
---
 winsup/cygwin/fhandler.h              |  1 +
 winsup/cygwin/fhandler_socket_unix.cc | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index 21e1df172..ad90cf33d 100644
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -1111,6 +1111,7 @@ class fhandler_socket_unix : public fhandler_socket
   int getsockname (struct sockaddr *name, int *namelen);
   int getpeername (struct sockaddr *name, int *namelen);
   int shutdown (int how);
+  int open (int flags, mode_t mode = 0);
   int close ();
   int getpeereid (pid_t *pid, uid_t *euid, gid_t *egid);
   ssize_t recvmsg (struct msghdr *msg, int flags);
diff --git a/winsup/cygwin/fhandler_socket_unix.cc b/winsup/cygwin/fhandler_socket_unix.cc
index 9f7f86c47..eedb0847e 100644
--- a/winsup/cygwin/fhandler_socket_unix.cc
+++ b/winsup/cygwin/fhandler_socket_unix.cc
@@ -1208,6 +1208,11 @@ fhandler_socket_unix::~fhandler_socket_unix ()
 int
 fhandler_socket_unix::dup (fhandler_base *child, int flags)
 {
+  if (get_flags () & O_PATH)
+    /* We're viewing the socket as a disk file, but fhandler_base::dup
+       suffices here. */
+    return fhandler_base::dup (child, flags);
+
   if (fhandler_socket::dup (child, flags))
     {
       __seterrno ();
@@ -1801,9 +1806,23 @@ fhandler_socket_unix::shutdown (int how)
   return 0;
 }
 
+int
+fhandler_socket_unix::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_unix::close ()
 {
+  if (get_flags () & O_PATH)
+    return fhandler_base::close ();
+
   HANDLE evt = InterlockedExchangePointer (&cwt_termination_evt, NULL);
   HANDLE thr = InterlockedExchangePointer (&connect_wait_thr, NULL);
   if (thr)
@@ -2281,6 +2300,11 @@ fhandler_socket_unix::ioctl (unsigned int cmd, void *p)
 int
 fhandler_socket_unix::fcntl (int cmd, intptr_t arg)
 {
+  if (get_flags () & O_PATH)
+    /* We're viewing the socket as a disk file, but
+       fhandler_base::fcntl suffices here. */
+    return fhandler_base::fcntl (cmd, arg);
+
   int ret = -1;
 
   switch (cmd)