logstash-output-syslog-3.0.5 with protocol UDP and an IPv6 address fails in connect

[BenAveling]

When using logstash-output-syslog-3.0.5 with protocol UDP and an IPv6 address, it fails in connect, at line 209 of logstash/vendor/bundle/jruby/2.5.0/gems/logstash-output-syslog-3.0.5/lib/logstash/outputs/syslog.rb:

i.e.

208: socket = UDPSocket.new
209: socket.connect(@host, @port) <-- fails here, if @host is an IPv6 address.

If I change line 208 to explicitly use IPv6 it works for IPv6 addresses.

i.e.

208: socket = UDPSocket.new(Socket::AF_INET6)
209: socket.connect(@host, @port) <-- this now works when @host is an IPv6 address.

Obviously, that breaks IPv4, which isn't an issue for me, but a proper fix should handle both IPv4 and IPv6.

Absent my change, it works with IPv4, and it works with TCP, it's just the combination of UDP and IPv6 that fails.

This has been/is being discussed at https://discuss.elastic.co/t/logstash-output-syslog-3-0-5-not-sending-udp-over-ipv6/307279