Get ip address of logstash forwarder

is there a way to get the ip address of the logstash-forwarder node?

I tried using %{host} however that just gives me the short hostname. I'm tried to do some geoip lookups and without the fqdn or preferably the ip address I'm unable to do the lookups. We have multiple domains that are used in this environment so I cant do a dns lookup without the fqdn. Regardless we don't really want to do use dns filter and assume that the server sending the logs is the same one as the one that comes up in a reverse dns check.

I found this article but this doesn't work with the 1.5 branch.

Regards,

Rory