prepareRequestFunction() sometimes have request.socket.remoteAddress undefined

[Jan Čurn]

When the client connection is closed too early, the request object passed to prepareRequestFunction() has socket.remoteAddress undefined, which can cause issues to users to the proxy-chain package. Since such connections are dead anyway, we should not pass them to prepareRequestFunction() and drop them right away.

For details why this happens, see nodejs/node#23858

[Szymon Marczak]

Attempting to fix this in 3106aee, after the first check we cannot reliably detect socket close since the address is cached and socket.readyState is open.

[Jan Čurn]

Thanks!