Add the ability to lookup the 3b PCP of a VLAN interface. Use it in toe_l2_resolve to fill up the complete vtag and not just the vid.

[np]

This is modeled after VLAN_TAG (which is mislabeled and just returns the
vid instead of the entire tag). I'm ok with changing the behavior of
VLAN_TAG to return the full tag including pcp but I went with a separate
VLAN_PCP to avoid surprising existing users of VLAN_TAG.

[kib]

I am fine with that, but I am not quite sure why do you want VLAN_PCP() at all. if_pcp can be directly accessed and used when it is != IFNET_PCP_NONE.

[mjoras]

sys/net/if_vlan.c

768

Do you want this to be safe across vlan interface removal? If so you need to have locked access here.

[np]

I decided to grab the PCP from the ifvlan (like VLAN_TAG does). I believe ifconfig ... vlanpcp <foo> updates this field.
ifconfig ... pcp <foo> updates the if_pcp field but I don't see any code that attempts to keep the ifvlan's pcp
and the ifnet's pcp in sync when the ifnet is a vlan ifnet.

[np]

sys/net/if_vlan.c

768

I want this to be as similar as possible to the vlan_tag a few lines above :-)