[Bridge] possible bridge regression in "bridge: implement [add/del]_slave ops"?

Alexander Stein alexander.stein at systec-electronic.com
Sun Jul 3 23:46:44 PDT 2011

On Thursday 30 June 2011 19:08:19 Stephen Hemminger wrote:
> On Thu, 30 Jun 2011 10:33:23 +0200
> Alexander Stein <alexander.stein at systec-electronic.com> wrote:
> > * echo $(pgrep rstpd) > /var/run/rstpd.pid
> > * brctl addbr br1
> > * echo 1 > /sys/class/net/br1/bridge/stp_state
> This bogus. You are running both kernel and spanning
> tree daemon at the same time!
> Doing the echo of 1 to stp_state forces kernel spanning
> tree. You want 2 which is what is supposed to be use for user
> mode spanning tree.

Well, at first sight you're right. But looking at the code at 
br_stp_set_enabled() in br_stp_if.c it doesn't matter which value you echo 
into stp_state, it just have to be non-zero
The detection of usermode oder kernelmode STP is done using the usermode 
helper (see br_stp_start). I tried echoing 1, 2 or even 5 into stp_state, with 
a working /sbin/bridge-stp I get 2 from stp_state each time.

Maybe it is valuable to change this odd behavior.


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