net: ipv6_stub: use ip6_dst_lookup_flow instead of ip6_dst_lookup

mainline inclusion
from mainline-v5.5-rc1
commit 6c8991f4
category: bugfix
bugzilla: 13690
CVE: CVE-2020-1749

-------------------------------------------------

ipv6_stub uses the ip6_dst_lookup function to allow other modules to
perform IPv6 lookups. However, this function skips the XFRM layer
entirely.

All users of ipv6_stub->ip6_dst_lookup use ip_route_output_flow (via the
ip_route_output_key and ip_route_output helpers) for their IPv4 lookups,
which calls xfrm_lookup_route(). This patch fixes this inconsistent
behavior by switching the stub to ip6_dst_lookup_flow, which also calls
xfrm_lookup_route().

This requires some changes in all the callers, as these two functions
take different arguments and have different return types.

Fixes: 5f81bd2e ("ipv6: export a stub for IPv6 symbols used by vxlan")
Reported-by: Xiumei Mu <xmu@redhat.com>
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Conflicts:
  include/net/addrconf.h
  drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
  net/core/lwt_bpf.c
  net/tipc/udp_media.c
  net/ipv6/addrconf_core.c
  net/ipv6/af_inet6.c
  drivers/infiniband/core/addr.c
[yyl: adjust context]

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Wenan Mao <maowenan@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>