I uploaded dhclient 3.0.6-2 which fixes two bugs:
dhclient-script only generates a new resolv.conf if the DHCP server
transmits a domain name. However, the DHCP specifications don't require
a DHCP server to do that. This was reported to ISC in 2004 IIRC and they
never even looked at it.
This patch fixes resolv.conf generation, such that resolv.conf is always
generated if the DHCP server transmits at least one DNS server. I
actually fixed this half a year ago, and didn't upload it.
I was trying to find this bug for over half a year and just now found
out it is dhclient's fault (partially).
dhclient/dhclient-script brings the interface down and up again on
several occasions. This was never a problem in the past, but with a
mac80211 driver, this results in an unusable interface until you
reassociate (the RUNNING flag in ifconfig is missing).
The interface was brought by dhclient-script down on occasions where
bringing it down isn't even necessary, but it suffices to simply delete
the ipv4 data (which was done anyway). This patch fixes the problem by
removing the "down" keyword from all ifconfig lines in dhclient-script,
as the script is never required to actually bring the interface down.
One of the occasions when dhclient would bring the interface down and up
again was a DHCPNAK. As a NAK is very common when you switch between
several wireless networks, as you may try to REQUEST a lease which has
not expired yet and get a NAK as the network you are on now is
different. This essentially broke all mac80211 driver when using
wireless roaming with dhclient and long lease times.