• Eric Dumazet's avatar
    vlan: allow null VLAN ID to be used · 05423b24
    Eric Dumazet authored
    We currently use a 16 bit field (vlan_tci) to store VLAN ID/PRIO on a skb.
    
    Null value is used as a special value, meaning vlan tagging not enabled.
    This forbids use of null vlan ID.
    
    As pointed by David, some drivers use the 3 high order bits (PRIO)
    
    As VLAN ID is 12 bits, we can use the remaining bit (CFI) as a flag, and
    allow null VLAN ID.
    
    In case future code really wants to use VLAN_CFI_MASK, we'll have to use
    a bit outside of vlan_tci.
    
    #define VLAN_PRIO_MASK         0xe000 /* Priority Code Point */
    #define VLAN_PRIO_SHIFT        13
    #define VLAN_CFI_MASK          0x1000 /* Canonical Format Indicator */
    #define VLAN_TAG_PRESENT       VLAN_CFI_MASK
    #define VLAN_VID_MASK          0x0fff /* VLAN Identifier */
    Reported-by: default avatarGertjan Hofman <gertjan_hofman@yahoo.com>
    Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    05423b24
vlan.h 4.52 KB