kern/116837: ifconfig tunX destroy: panic

[Bob Van Zant]

The following reply was made to PR kern/116837; it has been noted by GNATS.

From: Bob Van Zant <bob at veznat.com>
To: bug-followup at FreeBSD.org
Cc:  
Subject: Re: kern/116837: ifconfig tunX destroy: panic
Date: Sun, 6 Jan 2008 22:46:09 +0530

 My FreeBSD 7.0-PRERELEASE box has been running into this problem a lot  
 recently when I reset my ppp connection to counteract the effects of  
 having a very poor ISP. I would like to fix this bug. Is there anyone  
 that can help me identify what the proper behavior is?
 
 In my case the repro is something along the lines of:
 
 - Create ppp connection (tun0)
 - Create six-to-four connection (stf0)
 - The ppp connection gets wedged
 - /etc/rc.d/ppp stop
 - ifconfig tun0 destroy
 -     kernel panic
 
 My hunch is that the stf0 interface being "on top" of tun0 is causing  
 the problem. I've changed the script, maybe the panic will stop  
 happening.
 
 But what should the behavior be? Should the if_tun code make an  
 attempt to clean up whatever it can and then just destroy the  
 interface like requested? Or should it return some sort of error and  
 the ifconfig request to destroy the interface fails?
 
 The if_tap code appears to have the same assert in its destroy  
 function and we may want to fix that as well.
 
 I tend to get a few spare hours during any given week to play with  
 these sorts of things and I'd like to be able to help out with this  
 one. Any sort of direction folks can give in working towards a  
 solution will be appreciated.
 
 -Bob