datapath: Fix cached ct with helper.

datapath: Fix cached ct with helper.

Upstream commit:
    commit 16ec3d4fbb967bd0e1c8d9dce9ef70e915a86615
    Author: Joe Stringer <joe@ovn.org>
    Date:   Wed May 11 10:29:26 2016 -0700

    openvswitch: Fix cached ct with helper.

    When using conntrack helpers from OVS, a common configuration is to
    perform a lookup without specifying a helper, then go through a
    firewalling policy, only to decide to attach a helper afterwards.

    In this case, the initial lookup will cause a ct entry to be attached to
    the skb, then the later commit with helper should attach the helper and
    confirm the connection. However, the helper attachment has been missing.
    If the user has enabled automatic helper attachment, then this issue
    will be masked as it will be applied in init_conntrack(). It is also
    masked if the action is executed from ovs_packet_cmd_execute() as that
    will construct a fresh skb.

    This patch fixes the issue by making an explicit call to try to assign
    the helper if there is a discrepancy between the action's helper and the
    current skb->nfct.

    Fixes: cae3a2627520 ("openvswitch: Allow attaching helpers to ct action")
    Signed-off-by: Joe Stringer <joe@ovn.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Jarno Rajahalme <jarno@ovn.org>
Fixes: 11251c170d92 ("datapath: Allow attaching helpers to ct action")
Signed-off-by: Jarno Rajahalme <jarno@ovn.org>
Acked-by: Jesse Gross <jesse@kernel.org>