Handle sockets that have been shut down about hickory-dns

[djc]

Yes, breaking out of the loop for that scenario seems reasonable. Would you be able to send a PR for that?

[djc]

Why are closing all of the process sockets like that? What is the purpose of doing so?

[dlon]

I've seen sockets being closed/shutdown randomly on a few machines, but I can't tell you why. It might be something that the OS is doing. Regardless, it probably makes no sense to continue to receive/send on them, right?

[bluejekyll]

Seems like we should be treating this error differently, but, if the server socket is closing, that would imply the server can no longer be used. It would need to reopen the Socket. What is closing the socket?

To be clear, the socket registered as part of "register_listener" should be live as long as the server itself and never be closed until the server is shutdown.

[dlon]

Would it make sense to simply break in the case where ENOTCONN is returned here? (This probably needs to be handled for the non-UDP cases as well.)

I suspect that this issue might occur when the process is suspended under some circumstances. Can't tell you what they are since I haven't been able to reproduce this myself, so I'm just speculating.

Arguably, this case should be handled regardless, since any process (running as root) can call pid_shutdown_sockets to close the sockets. There's no way to gracefully handle this at the moment.