kern/85780: 'panic: bogus refcnt 0' in routing/ipv6

[Kris Kennaway]

>Number:         85780
>Category:       kern
>Synopsis:       'panic: bogus refcnt 0' in routing/ipv6
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Sep 06 04:10:11 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator:     Kris Kennaway
>Release:        7.0
>Organization:
FreeBSD
>Environment:
sparc64
>Description:
This panic occurred on an SMP sparc64 machine.

> panic: bogus refcnt 0
> cpuid = 0
> KDB: enter: panic
> [thread pid 15 tid 100003 ]
> Stopped at      kdb_enter+0x3c: ta              %xcc, 1
> db> wh
> Tracing pid 15 tid 100003 td 0xfffff8001fb75680
> panic() at panic+0x164
> rtfree() at rtfree+0x7c
> nd6_na_output() at nd6_na_output+0x4d0
> nd6_ns_input() at nd6_ns_input+0x704
> icmp6_input() at icmp6_input+0xc38
> ip6_input() at ip6_input+0xf5c
> netisr_processqueue() at netisr_processqueue+0x7c
> swi_net() at swi_net+0xdc
> ithread_loop() at ithread_loop+0x18c
> fork_exit() at fork_exit+0x94
> fork_trampoline() at fork_trampoline+0x8

  It uses ipv6 to e.g. mount nfs /home directories and for ssh traffic, but the machine seems to have been idle at the time of panic (no other processes active on the other CPUs, and nothing much else running on the system either).  core available.

>How-To-Repeat:
It's only happened once so far.
>Fix:
      
>Release-Note:
>Audit-Trail:
>Unformatted: