In message <20041224052255.GJ5287@che.ojctech.com>, David Young writes:
>On Thu, Dec 23, 2004 at 09:39:37PM -0500, Steven M. Bellovin wrote:
>> I'm running a very fresh -current on a Thinkpad T42 with an 802.11a/b/g 
>> card.  I also run ifwatchd, and I see that carrier on the ath interface 
>> is dropped/restored about once per minute.  Why is that?  At the 
>> moment, it's the active interface I'm using to get out to the world.
>
>If the interface idle, then maybe the AP is disconnecting you.  Will you
>see what's happening "on the air" at that time with 'tcpdump -ne -y
>ieee802_11 -i ath0' ?
>
>There is a radio calibration that Atheros does periodically.  Maybe it
>is that.
>


21:30:45.737792 Beacon () [1.0* 2.0* 5.5 11.0 Mbit] ESS CH: 1, PRIVACY
21:30:46.045003 Beacon () [1.0* 2.0* 5.5 11.0 Mbit] ESS CH: 1, PRIVACY
21:30:46.147399 Beacon () [1.0* 2.0* 5.5 11.0 Mbit] ESS CH: 1, PRIVACY
21:30:46.827858 ReAssoc Request (machshav) AP : 00:60:1d:22:5a:86
21:30:46.829417 ReAssoc Response AID(5) : PRIVACY : Succesful
21:30:47.069047 Beacon () [1.0* 2.0* 5.5 11.0 Mbit] ESS CH: 1, PRIVACY
21:30:47.478655 Beacon () [1.0* 2.0* 5.5 11.0 Mbit] ESS CH: 1, PRIVACY

There was a transition at 21:30:46, associated (I assume) with the 
ReAssoc messages.  The question is why this should generate carrier 
down/up transitions to ifwatchd.


		--Prof. Steven M. Bellovin, http://www.cs.columbia.edu/~smb