GRE driver incorrectly uses zero as a flag value. Zero is a perfectly
valid value for key, and the tunnel should match packets with no key only
with tunnels created without key, and vice versa.
This is a slightly visible change since previously it might be possible to
construct a working tunnel that sent key 0 and received only because
of the key wildcard of zero. I.e the sender sent key of zero, but tunnel
was defined without key.
Note: using gre key 0 requires iproute2 utilities v3.2 or later.
The original utility code was broken as well.
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
d208328765