Merge branch 'rt6_pmtu'

Martin KaFai Lau says:

====================
ipv6: Stop /128 route from disappearing after pmtu update

The series is separated from another patch series,
'ipv6: Only create RTF_CACHE route after encountering pmtu exception',
which can be found here:
http://thread.gmane.org/gmane.linux.network/359140

This series focus on fixing the /128 route issues.  It is currently targeted
for net-next due to the number of code churn but it is also applicable
to net (should be without conflict).  The original reported problem can be
found here:
http://thread.gmane.org/gmane.linux.network/348138

Patch 01 and 02 are to prepare the fib6 search to expect both the
RTF_CACHE clone and its original route exist at the same fib6_node.

Patch 03 fixes the /128 route disappearing bug.

Patch 04 and 05 stop rt6_info from using the inet_peer's metrics to
avoid the /128 routes (like the /128 clone and its original route)
from stepping on each others' metrics.

The second patch is by 'Steffen Klassert <steffen.klassert@secunet.com>'
which I pulled off from netdev.  The third patch is also mostly by
Steffen with one minor optimization.

Many thanks to Hannes Frederic Sowa <hannes@stressinduktion.org> on
reviewing the patches and giving advice.
====================

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