fluent/fluentd — pull request #391 by repeatedly (2014-07-28 14:19:16+00:00)
Title: Add include_source_host options to in_syslog. fixes #390

See issue #390.
There are some CISCO devises who generate syslog message which doesn't contain hostname or ip.

I'm not sure which is better, IP address or hostname.

http://docs.ruby-lang.org/ja/2.1.0/method/IPSocket/i/addr.html