2 When NICs use VLAN stripping on receive they must pass a pointer to a
3 \fBvlan_group\fR when reporting the stripped tag to the networking
4 core. If no \fBvlan_group\fR is in use then some drivers just drop
5 the extracted tag. Drivers are supposed to only enable stripping if a
6 \fBvlan_group\fR is registered but not all of them do that.
9 On receive, some drivers handle priority tagged packets specially and
10 don't pass the tag onto the network stack at all, so Open vSwitch
11 never has a chance to see it.
14 Some drivers size their receive buffers based on whether a
15 \fBvlan_group\fR is enabled, meaning that a maximum size packet with a
16 VLAN tag will not fit if no \fBvlan_group\fR is configured.
19 On transmit, some drivers expect that VLAN acceleration will be used
20 if it is available, which can only be done if a \fBvlan_group\fR is
21 configured. In these cases, the driver may fail to parse the packet
22 and correctly setup checksum offloading or TSO.