On 9/24/2020 8:01 AM, Michael McMahon wrote:
> 
> 
> On 24/09/2020 12:26, Ken Brown wrote:
>> 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://urldefense.com/v3/__https://cygwin.com/pipermail/cygwin/2020-June/245088.html__;!!GqivPVa7Brio!P7lIFI4rYAtWh8_DtCbRCxT-M_E4vwQ0qwzQ0p656T73BpJ0jbUkLI_bXdA6mmSL9lJcSQ$ 
>>
>> 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.
>>
> 
> Thanks for the info. It's mainly about recognition of sockets for
> regular commands. Since these objects can exist on Windows filesystems
> now, potentially created by any kind of Windows application,
> it would be great if Cygwin could handle them, irrespective of whether
> the Cygwin development environment does. Though that sounds like a
> good idea too.

I think this has a simple fix (attached), but I can't easily test it because 
your test program doesn't compile for me.  First, I got

$ gcc -o native_unix_socket native_unix_socket.c
native_unix_socket.c:5:10: fatal error: WS2tcpip.h: No such file or directory
     5 | #include <WS2tcpip.h>
       |          ^~~~~~~~~~~~
compilation terminated.

I fixed this by making the include file name lower case.  (My system is case 
sensitive, so it matters.)

Next:

$ gcc -o native_unix_socket native_unix_socket.c
native_unix_socket.c:8:10: fatal error: afunix.h: No such file or directory
     8 | #include <afunix.h>
       |          ^~~~~~~~~~
compilation terminated.

There's no file afunix.h in the Cygwin distribution, but I located it online and 
pasted in the contents.  The program now compiles but fails to link:

$ gcc -o native_unix_socket native_unix_socket.c
/usr/lib/gcc/x86_64-pc-cygwin/10/../../../../x86_64-pc-cygwin/bin/ld: 
/tmp/cc74urPr.o:native_unix_socket.c:(.text+0x3b): undefined reference to 
`__imp_WSAStartup'
/tmp/cc74urPr.o:native_unix_socket.c:(.text+0x3b): relocation truncated to fit: 
R_X86_64_PC32 against undefined symbol `__imp_WSAStartup'
/usr/lib/gcc/x86_64-pc-cygwin/10/../../../../x86_64-pc-cygwin/bin/ld: 
/tmp/cc74urPr.o:native_unix_socket.c:(.text+0xf2): undefined reference to 
`__imp_WSAGetLastError'
/tmp/cc74urPr.o:native_unix_socket.c:(.text+0xf2): relocation truncated to fit: 
R_X86_64_PC32 against undefined symbol `__imp_WSAGetLastError'
/usr/lib/gcc/x86_64-pc-cygwin/10/../../../../x86_64-pc-cygwin/bin/ld: 
/tmp/cc74urPr.o:native_unix_socket.c:(.text+0x13d): undefined reference to 
`__imp_WSAGetLastError'
/tmp/cc74urPr.o:native_unix_socket.c:(.text+0x13d): relocation truncated to fit: 
R_X86_64_PC32 against undefined symbol `__imp_WSAGetLastError'
collect2: error: ld returned 1 exit status

This is probably easy to fix too, but I don't feel like tracking it down. 
Please send compilation instructions (that use Cygwin tools).

Ken