On 9/23/2020 7:25 AM, Michael McMahon via Cygwin wrote:
Hi,
I searched for related issues but haven't found anything.
I am having some trouble with Windows native Unix domain sockets
(a recent feature in Windows 10 and 2019 server) and Cygwin.
I think I possibly know the cause since I had to investigate a similar
looking issue on another platform built on Windows.
The problem is that cygwin commands don't seem to recognise native Unix
domain sockets correctly. For example, the socket "foo.sock" should
have the same ownership and similar permissions to other files
in the example below:
$ ls -lrt
total 2181303
-rw-r--r-- 1 mimcmah None 1259 Sep 23 10:22 test.c
-rwxr-xr-x 1 mimcmah None 3680 Sep 23 10:22 test.obj
-rwxr-xr-x 1 mimcmah None 121344 Sep 23 10:22 test.exe
-rw-r----- 1 Unknown+User Unknown+Group 0 Sep 23 10:23 foo.sock
-rw-r--r-- 1 mimcmah None 144356 Sep 23 10:27 check.ot
A bigger problem is that foo.sock can't be deleted with the cygwin "rm"
command.
$ rm -f foo.sock
rm: cannot remove 'foo.sock': Permission denied
$ chmod 777 foo.sock
chmod: changing permissions of 'foo.sock': Permission denied
$ cmd /c del foo.sock
But, native Windows commands are okay, as the third example shows.
I think the problem may relate to the way native Unix domain sockets are
implemented in Windows and the resulting special handling required.
They are implemented as NTFS reparse points and when opening them
with CreateFile, you need to specify the FILE_FLAG_OPEN_REPARSE_POINT
flag. Otherwise, you get an ERROR_CANT_ACCESS_FILE. There are other
complications unfortunately, which I'd be happy to discuss further.
But, to reproduce it, you can compile the attached code snippet
which creates foo.sock in the current directory. Obviously, this
only works on recent versions of Windows 10 and 2019 server.
Cygwin doesn't currently support native Windows AF_UNIX sockets, as you've
discovered. See
https://cygwin.com/pipermail/cygwin/2020-June/245088.html
for the current state of AF_UNIX sockets on Cygwin, including the possibility of
using native Windows AF_UNIX sockets on systems that support them.
If all you want is for Cygwin to recognize such sockets and allow you to apply
rm, chmod, etc., I don't think it would be hard to add that capability. But I
doubt if that's all you want.
Further discussion of this will have to wait until Corinna is available.
Ken
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