Hi Xin,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on ipsec-next/master]

url:    https://github.com/0day-ci/linux/commits/Xin-Long/xfrm-support-ipip-and-ipv6-tunnels-in-vti-and-xfrmi/20200630-154042
base:   https://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec-next.git master
config: x86_64-lkp (attached as .config)
compiler: gcc-9 (Debian 9.3.0-14) 9.3.0
reproduce (this is a W=1 build):
        # save the attached .config to linux build tree
        make W=1 ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>, old ones prefixed by <<):

>> ERROR: modpost: "xfrm6_tunnel_spi_lookup" [net/ipv6/ip6_vti.ko] undefined!

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0-DAY CI Kernel Test Service, Intel Corporation
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