Re: em(4) losing link when if_bridge(4) addm/deletem are used

On Wed, Mar 28, 2007 at 03:30:45PM -0700, Jeremy Chadwick wrote:
On Thu, Mar 29, 2007 at 09:37:09AM +1200, Andrew Thompson wrote:
On Tue, Mar 27, 2007 at 08:33:27PM -0700, Jeremy Chadwick wrote:
In the midst of the madness, I found that when doing either of the
following commands...

ifconfig bridge0 addm em1
ifconfig bridge0 deletem em1

...I see the entire em1 interface completely reset, bringing down link,
then up again shortly after. The logs on my switch also confirm this.

The only other thing the bridge does to the interface when removing it
is to reinstate IFCAP_TXCSUM, which is disabled when the interface is
bridged. If you manually toggle this with ifconfig do you get the same
result?

Bingo.

medusa# ifconfig em1 -txcsum
medusa# ifconfig em1
em1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
options=8<VLAN_MTU>
inet 10.0.0.2 netmask 0xffffff00 broadcast 10.0.0.255
ether 00:30:48:71:60:6b
media: Ethernet autoselect
status: no carrier
medusa# grep em1 /var/log/messages
Mar 28 15:29:34 medusa kernel: em1: link state changed to DOWN
Mar 28 15:29:36 medusa kernel: em1: link state changed to UP

As a workaround you could remove txcsum at boot, then the bridge will
not toggle it. Long term you could prod the em(4) maintainer to see if
this can be resolved.


Andrew
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