[ovs-git] [openvswitch/ovs] 88a28b: datapath: Fix build errors for 4.9.172+ kernels

[yifsun]

  Branch: refs/heads/master
  Home:   https://github.com/openvswitch/ovs
  Commit: 88a28bbe5959a09d99d15ee2e6ee4714f9682ce8
      https://github.com/openvswitch/ovs/commit/88a28bbe5959a09d99d15ee2e6ee4714f9682ce8
  Author: Yifeng Sun <pkusunyifeng at gmail.com>
  Date:   2019-06-07 (Fri, 07 Jun 2019)

  Changed paths:
    M datapath/linux/compat/nf_conntrack_reasm.c

  Log Message:
  -----------
  datapath: Fix build errors for 4.9.172+ kernels

4.9.172+ kernel backported upstream patch 70b095c843266
("ipv6: remove dependency of nf_defrag_ipv6 on ipv6 module")
and this caused compilation errors of OVS kernel module.

This patch fixes it by checking and using new functions
introduced by the upstream patch.

Travis tests passed at
https://travis-ci.org/yifsun/ovs-travis/builds/536527230
with latest Linux kernel version.

In addition, this patch doesn't introduce failed tests for latest kernels
of Ubuntu (bionic, trusty, xenial), fedora, centos 73, rhel (74, 75, 76).

Reported-by: Ilya Maximets <i.maximets at samsung.com>
Acked-by: Yi-Hung Wei <yihung.wei at gmail.com>
Signed-off-by: Yifeng Sun <pkusunyifeng at gmail.com>
Signed-off-by: Ben Pfaff <blp at ovn.org>