ping_v6_sendmsg does not set flowi6_oif in response to
sin6_scope_id or sk_bound_dev_if, so it is not possible to use
these APIs to ping an IPv6 address on a different interface.
Instead, it sets flowi6_iif, which is incorrect but harmless.
Stop setting flowi6_iif, and support various ways of setting oif
in the same priority order used by udpv6_sendmsg.
[Backport of net 5e45789698]
Bug: 29370996
Change-Id: Ibe1b9434c00ed96f1e30acb110734c6570b087b8
Tested: https://android-review.googlesource.com/#/c/254470/
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
0e806c83bc