82599 receiving packets with vlan tag=0 (vlan strip problem)?

[Ryan Stone]

If vlan stripping is disabled on the 82599(i.e. RXDCTL.VME is 0 for
that queue is clear) and a vlan-tagged packet is received, then the
descriptor for that packet will have the VP bit set even though the
vlan was not stripped, and the VLAN Tag field in the descriptor is set
to 0.  ixgbe_rxeof will see that the VP bit is set and set the
M_VLANTAG on the mbuf, and put 0 in m_pkthdr.ether_vtag.  This means
that the stack will treat the packet as if it was double vlan tagged,
with outer tag being 0.

Ryan Stone