How does roslaunch determine a remote node's hostname? Can it be overridden?

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I've come across a hostname problem in the process of trying to set up the launch of a remote node in a pair of computers using mdns.

It appears that the uri of the remote node at some point is re-synthesized by asking the remote node its hostname instead of using the original address from the machine tag in the launch file.

The reason I believe this is that I'm able to create a roslaunch with a machine tag that successfully creates the ssh connection to let's say foo.local but then when it connects it complains about not being able to connect to contact it's own server http://foo:5xxxx implying that it's ignoring the original hostname foo.local and perhaps has used the machine's own idea of what it's host name is to connect.