kern/162558: [dummynet] [panic] seldom dummynet panics

[Eugene Grosbein]

The following reply was made to PR kern/162558; it has been noted by GNATS.

From: Eugene Grosbein <egrosbein at rdtc.ru>
To: bug-followup at FreeBSD.ORG
Cc:  
Subject: Re: kern/162558: [dummynet] [panic] seldom dummynet panics
Date: Wed, 15 Feb 2012 19:25:43 +0700

 Hi!
 
 The source of this problem seems to be famous 'dangling pointer' problem:
 - mbufs with packets from PPPoE users sometimes stall within dummynet queues,
 - then user disconnects, its ngX interface get destroyed,
 - then dummynet attempts to dereference its ifp pointer and panic occurs.
 
 There is workaround consisting of several tunnables eliminating races:
 
 - net.isr.bindthreads=1 in /boot/loader.conf;
 - net.isr.direct=1 and net.isr.direct_force=1 in /etc/sysctl.conf
   (default)
 
 Plus, use recent 8.2-STABLE as it contains some netgraph fixes
 for bugs that lead to panics in 8.2-RELEASE and early 8.2-STABLE versions.
 
 With these precautions I run my routers rock stable for months.
 
 Eugene Grosbein