[RFC net 0/2] ipv6: Avoid restaring fib6_lookup() for RTF_CACHE hit

I am trying to understand why there is a need to restart fib6_lookup() after
getting rt with RTF_CACHE.

I have adapted the davem's udpflood test
(https://git.kernel.org/pub/scm/linux/kernel/git/davem/net_test_tools.git) to
support IPv6 and here is the result:

#root > time ./udpflood -l 20000000 -c 250 2401:db00:face:face::2

Before:
real    0m33.224s
user    0m2.941s
sys     0m30.232s

After:
real    0m31.517s
user    0m2.938s
sys     0m28.536s