kern/126695: rtfree messages and network disruption upon use of if_bridge(4)

Sean Farley scf at
Wed Aug 20 21:20:03 UTC 2008

>Number:         126695
>Category:       kern
>Synopsis:       rtfree messages and network disruption upon use of if_bridge(4)
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Aug 20 21:20:02 UTC 2008
>Originator:     Sean Farley
>Release:        FreeBSD 7.0-STABLE i386
System: FreeBSD 7.0-STABLE FreeBSD 7.0-STABLE #0 r181375M: Thu Aug 7 10:14:36 CDT 2008 sean at i386

Multiple machines exhibit this:
1. Athlon XP (i386, two em and one sk NIC's)
2. Intel Q6600 (i386, one em NIC)
2. Intel Core 2 Duo 6300 (amd64, one bge NIC)

On a 7-STABLE (built August 7th), I have noticed messages appearing in
Aug  7 15:07:17 thor kernel: rtfree: 0xc7143a2c has 2 refs
Aug  7 15:07:19 thor last message repeated 2 times
Aug  7 15:09:28 thor last message repeated 3 times
Aug  7 15:11:54 thor last message repeated 9 times

This happens if I set up a bridge to have em0 and tap0 such as from:
ifconfig bridge0 create
ifconfig bridge0 addm em0
ifconfig bridge0 addm tap0

When I start QEMU on tap0, I would immediately lose IPv6 on em0 and
eventually IPv4 would go away.  I would get a lot more of messages about
rtfree with QEMU started.

>From experimentation (and some luck), I found that if I reversed the
devices on a newly created bridge then the rtfree messages would go
away, but I would have problems with tap0.  The workaround:  create two
tap devices tap0 and tap1 and add to bridge0 in the order of tap1, tap0
and em0.

On another system, I noticed that a bridge between real NIC's (em1 and
sk0) also reports an rtfree message during boot.

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