Native image: add support for unix domain sockets

[mostroverkhov]

Motivation:

unix domain sockets with graalvm native image require additional reflection configuration.

Modification:

add unix domain sockets graalvm configuration in reflect-config.json.

Result:

unix domain sockets with graalvm native image work out of the box.

[chrisvest]

The ni_metadata.sh should be capturing what we need and generate those files, AFAIU. Maybe the tests we run have a blind spot for unix domain sockets?

CC @gradinac

[gradinac]

The ni_metadata.sh script is only used for Netty 5 IIRC well. I think we used it to collect the initial Netty 4 metadata that we provide in the reachability metadata repository, however this entry does seem to be missing even there. My guess is that the metadata for the epoll suite got wrongly filtered by the agent as I could find the following reference to for example io.netty.channel.epoll.EpollDomainSocketChannel in the following test: https://github.com/netty/netty/blob/4.1/transport-native-epoll/src/test/java/io/netty/channel/epoll/EpollSocketTestPermutation.java#L229. I assume there may be more, this is just one where we're most likely to have need for reflective metadata

[normanmaurer]

@gradinac so correct me if I am wrong but you suggest we should just pull this in ?

[gradinac]

@normanmaurer I think it may be worthwhile pulling this in, especially because the handcrafted metadata conditions here seem correct (only even pull this in if Native from epoll is reachable)

[normanmaurer]

Thanks a lot