RFR 8231187: SelectorProvider.inheritedChannel() returns TCP socket channel for Unix domain socket

[Alan Bateman]

On 20/09/2019 10:53, Michael McMahon wrote:
> Hi,
>
> This issue was reported through a recent discussion proposing an API 
> for Unix domain
> sockets. It fixes the current erroneous behavior where TCP type 
> SocketChannels are returned
> and instead returns a Channel type which handles connected AF_UNIX 
> sockets specifically.
>
> The fix also enables the whole inherited channel mechanism for Mac, 
> which up to now
> has not been working.
>
> http://cr.openjdk.java.net/~michaelm/8231187/webrev.1/index.html
Yes, I remember that bug came up in the proposal to add the API so it's 
good to get it fixed.

I skimmed through the webrev. The async close doesn't look right, mostly 
missing preClose and the final close by the last thread doing I/O. The 
Unix implementation of SourceChannelImpl or SinkChannelImpl are the 
simplest examples to follow if you need it. The main issues are:

- need a state field to track that the channel is closing
- endRead need to close the channel when the state is_ST_CLOSING and 
there is no writer (the opposite for reader)
- implCloseChannel should only close if reader and writer are both 0, 
otherwise it should preClose and signal the reader and/or writer.

A minor nit is that getFDVal can be removed, and getFD can be private as 
the channel doesn't implement SelChImpl.

As a precaultion, createChannel could return null if the address family 
is AF_UKNOWN.

-Alan.