Problems with 6.2-PRE and udp applications - dhcpd and named

[Robert Watson]

On Fri, 13 Oct 2006, Jonathan Feally wrote:

> I have a P4 2.8 box running on an intel MB with a em0 acting as a firewall. 
> The em0 has multiple tagged vlans on it, no ip assigned to main interface. 
> Almost clockwork now, 6-7 days after bootup named or dhcpd completly locks 
> up. I can't even kill -9 the apps. I have recompiled both apps since 
> upgrading. I have only made two changes to this system around the same time. 
> 1.  Removed 2nd em nic that had only 1 network connected not vlan tagged. 2. 
> Upgraded to 6.2-PRE
>
> Has anyone else had these problems? I am going to try running the system 
> with the internet connection not tagged to see if that helps.

I've not seen this on any boxes.  The usual debugging path here is to:

(1) Look at the process wait channel in ps axl.

(2) Compile KDB/DDB into the kernel, and do a kernel stack trace of the
     process.

Once you know what the kernel thread associated with the process is doing, we 
can attempt to figure out why it's doing it.

Robert N M Watson
Computer Laboratory
University of Cambridge