Dummynet pipe cascades

[Luigi Rizzo]

On Fri, May 23, 2014 at 03:53:18PM +0200, Patrick Zwickl wrote:
> Dear all,
> 
> I am currently experimenting with ipfw dummynet features (coming rather from the netem tc corner; so being new to dummynet and apologise for these kind of questions) and was wondering how to syntactically achieve "build cascades of pipes? listed on [1]?s front page. Unfortunately, I could not find a minimal example for this in the documentation (or I missed the point).
> 
> Background: I am currently looking for concepts allowing me to put some traffic into a pipe being followed by several queues, the scheduler and then reinserted into another pipe (optimally as clean as possible). So, basically, a cascade of pipes, optimally being able to consume from different other pipes or interfaces. From the statement in [1], I assume ipfw + dummynet could be the perfect playground for this, but from the syntax it was not clear to me how this is done.
> 
> Any pointer to a minimal example or any reading recommendation would be highly appreciated (maybe I have been searching the wrong channels so far). Thanks in advance for reading and potentially commenting :)

the trick to enable cascades is to set the sysctl variable
	net.inet.ip.fw.one_pass=0
(or equivalent in linux, /sys/modules/...)
so that packets coming out from a pipe re-enter the
firewall at the next rule.

cheers
luigi