David S. Miller writes:

 > You cannot find the longest matching prefix and just use that.
 > 
 > Rather, you must iterate through all matching prefixes in the
 > table from longest to shortest, trying fib_semantic_match() on
 > each one until it says OK.

 You're right we have to match semantics then first after that return 
 longest prefix to comply w. current matching.


 > This makes using a new algorithm very non-trivial.

 Yes and will take resources compared to simple longest prefix.

 > Probably what you should do is keep an array on the function
 > stack, recording shorter prefix entries you see on your walk
 > down to the longest matching prefix.  Then you process the array
 > one entry at a time back to the root, trying fib_semantic_match()
 > on each one.

 We have backtracking as we search to leaves and as leaves does not 
 always has a matching prefix.  So we have to look into how semantics 
 match can be done here instead and backtrack until we got a semantics 
 match. Was about to test w. ipv6 to start with due to ipv4 complexity.
 Anyway ipv4 fib-code is cleaner now.

 Cheers.
						--ro