[newlib-cygwin] Cygwin: AF_LOCAL: set appropriate errno on system calls

[Ken Brown <kbrown at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=141437d37440572b5452e941df3d4454f0c4378b

commit 141437d37440572b5452e941df3d4454f0c4378b
Author: Ken Brown <kbrown@cornell.edu>
Date:   Thu Jan 23 15:11:15 2020 -0500

    Cygwin: AF_LOCAL: set appropriate errno on system calls
    
    If an AF_LOCAL socket is opened with O_PATH, all socket system calls
    that take a file descriptor argument fail on the resulting descriptor.
    Make sure that errno is set as on Linux for those calls that are
    implemented on Linux.  In almost all cases it is ENOTSOCK.  There are
    two exceptions:
    
    - sockatatmark(3); errno is EBADF.
    
    - bindresvport(3); errno is EAFNOSUPPORT if the second argument sin
      (of type struct sockaddr_in *) is non-NULL and satisfies
      sin->sin_family == AF_INET.
    
    Finally, there are two BSD socket system calls implemented on Cygwin
    but not Linux: getpeereid(3) and bindresvport_sa(3).  Set errno to
    ENOTSOCK for these for consistency with the majority of the other
    calls.

Diff:
---
 winsup/cygwin/net.cc | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/winsup/cygwin/net.cc b/winsup/cygwin/net.cc
index 437712c..d9f51bf 100644
--- a/winsup/cygwin/net.cc
+++ b/winsup/cygwin/net.cc
@@ -65,8 +65,11 @@ get (const int fd)
 
   fhandler_socket *const fh = cfd->is_socket ();
 
-  if (!fh)
-    set_errno (ENOTSOCK);
+  if (!fh || (fh->get_flags () & O_PATH))
+    {
+      set_errno (ENOTSOCK);
+      return NULL;
+    }
 
   return fh;
 }
@@ -641,9 +644,17 @@ extern "C" int
 sockatmark (int fd)
 {
   int ret;
+  cygheap_fdget cfd (fd);
 
-  fhandler_socket *fh = get (fd);
-  if (fh && fh->ioctl (SIOCATMARK, &ret) != -1)
+  if (cfd < 0)
+    return -1;
+
+  fhandler_socket *const fh = cfd->is_socket ();
+  if (!fh)
+    set_errno (ENOTSOCK);
+  else if (fh->get_flags () & O_PATH)
+    set_errno (EBADF);
+  else if (fh->ioctl (SIOCATMARK, &ret) != -1)
     return ret;
   return -1;
 }