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
