net/enic: ignore VLAN inner type when it is zero

net/enic: ignore VLAN inner type when it is zero

When a VLAN pattern is present, the flow handler always copies its
inner_type to the match buffer regardless of its value (i.e. HW
matches inner_type against packet's inner ethertype). When inner_type
spec and mask are both 0, adding it to the match buffer is usually
harmless but breaks the following pattern used in some applications
like OVS-DPDK.

flow create 0 ingress ... pattern eth ... type is 0x0800 /
vlan tci spec 0x2 tci mask 0xefff / ipv4 / end actions count /
of_pop_vlan / ...

The VLAN pattern's inner_type is 0. And the outer eth pattern's type
actually specifies the inner ethertype. The outer ethertype (0x0800)
is first copied to the match buffer. Then, the driver copies
inner_type (0) to the match buffer, which overwrites the existing
0x0800 with 0 and breaks the app usage above.

Simply ignore inner_type when it is 0, which is the correct
behavior. As a byproduct, the driver can support the usage like the
above.

Fixes: ea7768b5bba8 ("net/enic: add flow implementation based on Flow Manager API")
Cc: stable@dpdk.org
Signed-off-by: Hyong Youb Kim <hyonkim@cisco.com>
Reviewed-by: John Daley <johndale@cisco.com>