- macOS 10.4+
The mbuf containing the packet.
The protocol family of the aux data to add.
0 upon success otherwise the errno error. ENXIO indicates that the vlan tag is not set.
This function is used by drivers that support hardware vlan tagging to determine which vlan this packet belongs to. To differentiate between the case where the vlan tag is zero and the case where there is no vlan tag, this function will return ENXIO when there is no vlan.