Re: Problems with OpenBSD dhclient

Kevin Oberman wrote:
> Since switching from the ISC DHCP client to OpenBSD on my laptop, I've
> been having some issues with managing my network connection. I'm running
> 7.0-current built yesterday (kernel and world.)
> 
> On a typical day I boot my system on  wired connection with a static
> address and gateway. Everything works fine. DHCP is not playing, yet.
> 
> When I go to a meeting, I want to switch to the wireless network. In the
> past I simply entered 'dhclient wi0' and I was up and running. The
> wireless uses DHCP, so dhclient would get the address and gateway along
> with DNS servers and instantiate these and I would be connected. The
> default route that had been in use previously was replaced with the DHCP
> supplied gateway. Switching back was a simple matter of '/etc/rc.d/netif
> start fxp0'.
> 
> While on the wireless network, I could roam with only brief loss of
> connectivity when I moved from one AP to another, but the wireless
> system soon "finds" me and I continue on-line with the same address and
> gateway. Even my ssh sessions are maintained.
> 
> Now life is not so nice with the OpenBSD dhclient.
> 
> When I switch to wireless, dhclient no longer replaces the default
> route. I need to take down my wired connection and flush routes before
> starting dhclient. Not a big deal, but an annoyance.

This sounds like the issue with dhclient not deleting it's routes on 
termination.

> 
> More serious is that I can't roam. When I move between APs, dhclient
> exits and I need to manually re-start it. I lose my SSH sessions. Ugh!

This should not be happening; dhclient should get a disassociate event, 
drop the lease, then get an associate when you join the new ap and 
immediately grab a new lease.  In fact this was the primary reason I 
wanted to switch to this new code in the first place.

> 
> Worse, I occasionally see my association drop momentarily when I am
> simply sitting and typing. Once again, dhclient dies and I must manually
> restart it and then re-establish my SSH and recover anything broken when
> the connection dropped. This is fairly serious! I don't understand what
> causes this, but it is infrequent which makes it hard to catch.
> 
> It looks like killing dhclient when the interface drops is not a good
> idea. At very least, it needs to give a little time for re-association
> before dropping the DHCP client.

Something is busted; I'll need to investigate.  If you want to help you 
can run ieee80211watch (from tools/tools/ath) while things happen and 
note the events that get sent by the kernel.

	Sam