AF_UNIX status report

[Ken Brown]

On 10/27/2020 5:43 AM, Corinna Vinschen wrote:
> On Oct 26 18:04, Ken Brown via Cygwin-developers wrote:
>> I've made at least rudimentary implementations of all the
>> fhandler_socket_unix functions (including those in select.cc) for which
>> there were previously only placeholders.
>>
>> I've pushed everything to topic/af_unix, including a merge with master as of
>> a couple days ago.
>>
>> I've cobbled together a few test programs and put them in
>> winsup/cygwin/socket_tests on the topic/af_unix branch.  I haven't taken the
>> time to automate the tests, so they all have to be run interactively.  There
>> is a Makefile to build the test programs and a README.txt that shows how to
>> run them.
>>
>> One thing I haven't yet done is to think about (or systematically test)
>> datagram sockets.  I'm sure there's quite a bit of code that won't work for
>> them.
>>
>> Aside from datagram sockets, there are still a few things that I'm working
>> on, but I'm close to the point where I could use some input:
>>
>> 1. I've littered the code in fhandler_socket_unix.cc and select.cc with
>> FIXME comments on which I'd like advice.
> 
> I'll look into it.
> 
>> 2. I haven't given any thought at all as to how to implement SCM_RIGHTS
>> ancillary data.  I could definitely use suggestions on that before I start
>> thrashing around.
> 
> I have only vague ideas at that point.  Assuming we can replace the
> socket implemantation with the pipe implementation, what we have is a
> pipe which can impersonate the peer at least from the server side, and
> it knows the client process.  This in turn can be used to duplicate
> handles.  So what we could do is to define fhandler methods which create
> a matching serialization  and deserialization of the fhandler data, plus
> duplicating the handles for the other process, sent over the pipe as
> admin package.  This must work in either direction, regardless if the
> server or the client sends the SCM_RIGHTS block.

This sounds reasonable.

I have no experience with serialization.  Do you happen to know of a good 
example that I could look at?

Thanks.

Ken