Merge branch 'connection-tracking-support-for-bridge'

Pablo Neira Ayuso says:

====================
connection tracking support for bridge

This patchset adds native connection tracking support for the bridge.

Patch #1 and #2 extract code from IPv4/IPv6 fragmentation core and
introduce the fraglist splitter. That splits a skbuff fraglist into
independent fragments.

Patch #3 and #4 also extract code from IPv4/IPv6 fragmentation core
and introduce the skbuff into fragments transformer. This can be used
by linearized skbuffs (eg. coming from nfqueue and ct helpers) as well
as cloned skbuffs (that are either seen either with taps or with bridge
port flooding).

Patch #5 moves the specific IPCB() code from these new fragment
splitter/transformer APIs into the IPv4 stack. The bridge has a
different control buffer layout and it starts using this new APIs in
this patchset.

Patch #6 adds basic infrastructure that allows to register bridge
conntrack support.

Patch #7 adds bridge conntrack support (only for IPv4 in this patch).

Patch #8 adds IPv6 support for the bridge conntrack support.

Patch #9 registers the IPv4/IPv6 conntrack hooks in case the bridge
conntrack is used to deal with local traffic, ie. prerouting -> input
bridge hook path. This cover the bridge interface has a IP address
scenario.

Before this patchset, only chance for people to do stateful filtering is
to use the `br_netfilter` emulation layer, that turns bridge frame into
IPv4/IPv6 packets and inject them into the IPv4/IPv6 hooks. Apparently,
this module allows users to use iptables and all of its feature-set from
the bridge, including stateful filtering. However, this approach is
flawed in many aspects that have been discussed many times. This is a
step forward to deprecate `br_netfilter'.

v2: Fix English typo in commit message.
v3: Fix another English typo in commit message.
====================

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