In message <20051002212557.GA17443@panix.com>, Thor Lancelot Simon writes:

>
>This is a bug in both iwi *and* in dhclient, one which has been fixed in
>many other network interface drivers.
>
>Dhclient should not ifconfig the interface up and down -- or, in fact,
>touch it with ifconfig *at all* -- if the IP address remains the same
>on renewal of the DHCP lease.

As I've written in the past, dhclient has the wrong model of how to 
handle the two separate problems of acquiring a layer 2 signal and 
getting an IP address.  The former is independent and may require 
things like speed selection, setting a WEP key or 802.11 mode, etc.  
After that's done, an address can be obtained.  Confusing the two 
exacerbates problems like this.

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