* - BOND_LINK_UP: carrier detected, updelay has passed.
* - BOND_LINK_FAIL: carrier lost, downdelay in progress.
* - BOND_LINK_DOWN: carrier lost, downdelay has passed.
* - BOND_LINK_BACK: carrier detected, updelay in progress.
*
* - BOND_LINK_UP: carrier detected, updelay has passed.
* - BOND_LINK_FAIL: carrier lost, downdelay in progress.
* - BOND_LINK_DOWN: carrier lost, downdelay has passed.
* - BOND_LINK_BACK: carrier detected, updelay in progress.
*