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Date: Wed, 3 Jun 2020 15:23:20 +0200
From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: AF_UNIX/AF_LOCAL
Message-ID: <20200603132320.GH6801@calimero.vinschen.de>
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On Jun  2 14:46, Kristian Ivarsson via Cygwin wrote:
> Hey folks (probably Corinna more specifically)
> 
> As far as I know the "unix domain socket implementation" is not really
> complete
> 
> We tried it and it didn't work for our purposes (the symptoms were UDP-like,
> i.e. it seemed that some messages were lost along the way (or possibly ended
> up in the wrong order)

That shouldn't occur because the current AF_UNIX implementation is using
AF_INET sockets under the hood, and it doesn't implement any packet
caching overriding the OS buffers.

> As far as I understand, Microsoft/WinSock support AF_UNIX/AF_LOCAL with (at
> least) SOCK_STREAM (I do not really know what system dependencies it
> requires though and thus the Cygwin implementation might not utilize that at
> all?)

If we'd only support W10, that might be ok, but as long as we support
Vista/7/8/8.1, we need something else.

> The branch topic/af_unix seems to address this issue, so our question is if
> anyone knows the status of the AF_UNIX/AF_LOCAL progress ?

This is the new AF_UNIX implementation using pipes under the hood.  I
started it quite some while ago but got thoroughly sidetracked and have
a lot other stuff on my plate.

The skeleton code is already in master.  The topic branch is a bit
outdated and split from master so some merging is needed.    It's built
into the Cygwin DLL with -D__WITH_AF_UNIX.

What this code needs is some dusting off and somebody picking it up
again.  Maybe in winter I have some time for that again, but it wouldn't
hurt to have somebody else with interest in the new implementation to
help.

Patches welcome!

Also, nothing speaks against a third implementation using native Windows
AF_UNIX sockets under the hood on systems supporting them, provided the
pipe implementation works on older systems, too.


Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
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