Merge branch 'ipv6-defrag-rbtree'

Peter Oskolkov says:

====================
net: IP defrag: use rbtrees in IPv6 defragmentation

Currently, IPv6 defragmentation code drops non-last fragments that
are smaller than 1280 bytes: see
commit 0ed4229b08c1 ("ipv6: defrag: drop non-last frags smaller than min mtu")

This behavior is not specified in IPv6 RFCs and appears to break compatibility
with some IPv6 implementations, as reported here:
https://www.spinics.net/lists/netdev/msg543846.html

This patchset contains four patches:
- patch 1 moves rbtree-related code from IPv4 to files shared b/w
IPv4/IPv6
- patch 2 changes IPv6 defragmenation code to use rbtrees for defrag
queue
- patch 3 changes nf_conntrack IPv6 defragmentation code to use rbtrees
- patch 4 changes ip_defrag selftest to test changes made in the
previous three patches.

Along the way, the 1280-byte restrictions are removed.

I plan to introduce similar changes to 6lowpan defragmentation code
once I figure out how to test it.
====================

Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>