tree 1342c672823d47bfb112fee63951af9f6a3eb590
parent b8c8430726e5bd552e01dacc5a44f3f83f7446ca
author David S. Miller <davem@davemloft.net> 1340958765 -0700
committer David S. Miller <davem@davemloft.net> 1340958996 -0700

ipv4: Elide fib_validate_source() completely when possible.

If rpfilter is off (or the SKB has an IPSEC path) and there are not
tclassid users, we don't have to do anything at all when
fib_validate_source() is invoked besides setting the itag to zero.

We monitor tclassid uses with a counter (modified only under RTNL and
marked __read_mostly) and we protect the fib_validate_source() real
work with a test against this counter and whether rpfilter is to be
done.

Having a way to know whether we need no tclassid processing or not
also opens the door for future optimized rpfilter algorithms that do
not perform full FIB lookups.

Signed-off-by: David S. Miller <davem@davemloft.net>