DL_NOTE_LINK_{UP,DOWN}

Device driver support for the DL_NOTE_LINK_UP and DL_NOTE_LINK_DOWN notification messages is required by the NWAM prototype in order to automatically detect plugging/unplugging of an ethernet cable. This requirement only affects ethernet drivers. The following sections provide more information about individual driver support of these notifications.

Drivers that support the notifications

Drivers that do not support the notifications

How to determine if your driver supports them

What to do if your driver does not support them

Drivers that support the notifications

 We have confirmed that the bge, e1000g and eri drivers support these notifications.

 Other drivers which are believed (based on code inspection) to support this are:

• ce
• chxge
• dmfe
• gem
• hme
• ibd
• ipge
• ixgb
• ixge
• nge
• nxge
• qfe
• rge
• rtls
• xge

Drivers that do not support the notifications

 The following drivers do not appear to support these notifications:

• bcme
• elxl
• ge
• iprb
• pcelx
• skge

How to determine if your driver supports them

 A simple way to determine if your driver does or does not support this feature is by checking the IFF_RUNNING flag in the ifconfig output. When the cable is plugged in, the IFF_RUNNING flag should be set, i.e. RUNNING should appear in the ifconfig output:

bge0: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 2

 When you unplug the cable, the IFF_RUNNING flag should be cleared within a couple seconds, thus the word RUNNING will not appear in the ifconfig output:

bge0: flags=1000803<UP,BROADCAST,MULTICAST,IPv4> mtu 1500 index 2

What to do if your driver does not support them

 These notifications are the signal to the nwam daemon that an ethernet interface has become available (the cable has been plugged in) or is no longer available (the cable has been unplugged). Therefore, if the driver does not send them, the nwam daemon cannot automatically react to these changes; instead, it believes that the ethernet interface is always available, and will never switch to an alternate interface.

 To force another interface to be used, you can change the order in which nwam attempts to bring up interfaces by editing /etc/nwam/llp. This file contains one line for each interface in the system; on a laptop with one ethernet interface, bge0, and one wireless interface, ath0, that file will look like

bge0   dhcp
ath0   dhcp

 The order of the entries matters; by default, wired interfaces will be listed first, as they are preferred over wireless. If you change the order, so that, for example, ath0 appears before bge0, that wireless interface will be preferred and thus configured first.

 After editing /etc/nwam/llp, you will need to restart the nwam service to force a reload of the file contents.