Currently, in TX direction, driver implements the TX VLAN offload
by checking the VLAN header in skb, and filling it into TX descriptor.
Usually it works well, but if enable inserting VLAN header based on
port, it may conflict when out_tag field of TX descriptor is already
used, and cause RAS error.

In RX direction, hardware supports stripping max two VLAN headers.
For vlan_tci in skb can only store one VLAN tag, when RX VLAN offload
enabled, driver tells hardware to strip one VLAN header from RX
packet; when RX VLAN offload disabled, driver tells hardware not to
strip VLAN header from RX packet. Now if port based insert VLAN
enabled, all RX packets will have the port based VLAN header. This
header is useless for stack, driver needs to ask hardware to strip
it. Unfortunately, hardware can't drop this VLAN header, and always
fill it into RX descriptor, so driver has to identify and drop it.
Signed-off-by: Jian Shen <shenjian15@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>