Eric Siegerman wrote:

I believe there is a dumper->taper connection, for direct-to-tape
dumps.  That's how I read docs/PORT.USAGE, anyway -- see the bits
on stream_server() and stream_client().  But both of those

Aha, yes, indeed.  That's correct.

processes run on the same host, so it's still hard to see how a
firewall could get between them.
Unless Amanda's running on the firewall machine itself -- which
I'd consider an unsafe idea anyway!

As many linux distributions ship with a firewall installed
and configured (just as MS Windows with a personal firewall)
it could indeed block traffic to its own sockets, when slightly
misconfigured, or with paranoid settings.