Unix domain sockets (UDS, AF_UNIX) in System.inheritedChannel() and elsewhere in Java

[Alan Bateman]

On 22/07/2019 09:16, František Kučera wrote:
>
> It is a stream or a datagram socket – just from different domain (UNIX 
> instead of INET or INET6) – but they work the same way. So yes, when I 
> create a stream or datagram unix domain socket e.g. in systemd (parent 
> process), I can inherit it in Java and get ServerSocketChannel or 
> DatagramChannel from System.inheritedChannel() and it really works. 
> Recently, I wrote an article about it: https://blog.frantovo.cz/c/372/ 
> – it is in Czech, but code and config examples should be readable to 
> anyone.
>
> :
>
> BTW: the inheritedChannel() JavaDoc says:
>
> > In addition to the network-oriented channels described, this method 
> may return other kinds of channels in the future.
>
Yes, we added this method in Java SE 5 with a view to supporting other 
channel types (e.g. console) in the future.

I'll get back to you on the other points soon but I was curious about 
your observation that the inheritedChannel returns a channels with 
"garbage" local/remote addresses when fd 0 is a Unix domain socket. The 
bug is that the probe is missing a call to getsockname that it needs to 
check if the family is AF_INET or AF_INET6. So we should minimally fix that.

-Alan