About the definition of new chains. In a new chain, I am unable to set
the in and out interfaces of the rules that make up the chain. Is there
a particular reason for it, or is it a bug? Or more to the point, I
consider it a bug, because I want to set it, but can’t.
Also, I can’t seem to select the loopback interface in the forward,
input and output chains.
And as for TCP flags, how do I set RST/SYN and URG/FIN for instance?