Merge branch 'ipv6-loopback'

Eric Dumazet says:

====================
ipv6: remove addrconf reliance on loopback

Second patch in this series removes IPv6 requirement about the netns
loopback device being the last device being dismantled.

This was needed because rt6_uncached_list_flush_dev()
and ip6_dst_ifdown() had to switch dst dev to a known
device (loopback).

Instead of loopback, we can use the (hidden) blackhole_netdev
which is also always there.

This will allow future simplfications of netdev_run_to()
and other parts of the stack like default_device_exit_batch().

Last two patches are optimizations for both IP families.
====================

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