RFR 8245194: Unix domain socket channel implementation

[Michael McMahon]

On 09/07/2020 15:14, Chris Hegarty wrote:
>
>
>> On 8 Jul 2020, at 11:07, Michael McMahon 
>> <michael.x.mcmahon at oracle.com <mailto:michael.x.mcmahon at oracle.com>> 
>> wrote:
>>
>>> ...
>>>
>>> My initial reaction to seeing verbiage like "Internet protocol 
>>> socket” and “unix domain socket”, is how does one know what type of 
>>> socket channel one has if passed an unbound channel? I wonder if a 
>>> SocketChannel::protocolFamily method is worth adding? It could be 
>>> used and linked to from some of the verbiage elsewhere to tighten 
>>> the spec. There could also be some tie in here with inheritedChannel 
>>> - if the protocol family is retrievable.
>> I did consider that question and had concluded that testing the type 
>> of the SocketAddress returned by getLocalAddress() would suffice for 
>> this. But, you're right that does not work for unbound channels. I'll 
>> add this to the API for now (for SocketChannel and 
>> ServerSocketChannel in the sandbox), to see what it looks like. 
>> Perhaps, for consistency it should be added to DatagramChannel too?
>
> That works for me.
>
> What is the signature of this method? `Optional<ProtocolFamily> 
> protocolFamily()` - or something else? If not optional ( or null ), 
> then what is the family of a channel created with the no-args open 
> method? We had some offline discussion about UNSPEC, and if we add 
> this method then it could be a reason to add an UNSPEC 
> StandardProtocolFamily.
>
"public ProtocolFamily getProtocolFamily()"

I think a channel will always have a ProtocolFamily. So, it shouldn't 
need to be Optional<>

The value on the no-args call depends on the preferIPv4Stack setting. 
INET if set INET6 if not,
depending on which of IPv4/IPv6 are supported obviously. Do you think 
all of this would need
to be documented explicitly?

Michael

> -Chris.
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