[Bridge] STP bug, loop not detetcted

[Stephen Hemminger]

On Mon, 12 May 2008 11:37:45 +0200
Joakim Tjernlund <joakim.tjernlund at transmode.se> wrote:

> 
> On Thu, 2008-05-08 at 14:58 +0200, Joakim Tjernlund wrote:
> > On Thu, 2008-05-08 at 14:13 +0200, Francesco Dolcini wrote:
> > > Joakim Tjernlund wrote:
> > > > On Thu, 2008-05-08 at 11:04 +0200, Francesco Dolcini wrote:
> > > >> cisco and others solved this kind of problem using proprietary 
> > > >> unidirectional link detection protocols (see cisco informational rfc 
> > > >> 5171 for example). No standard exists as far as I know (BFD rfc does not 
> > > >> consider the layer 2 case).
> > > > 
> > > > Are these proprietary unidirectional link detection protocols the only
> > > > way to solve the problem?
> > > spanning tree protocol, in the various IEEE incarnation (802.1D, 802.1Q) 
> > > and cisco (PVSTP) does not handle this problem, so an external mechanism 
> > > is needed.
> > 
> > Do they explicitly ban it? Otherwise I don't see why not the kernel STP
> > can be enchanted. You could even view it as an external mechanism.
> > 
> > > 
> > > > Would STP break if the interface was set to "non forwarding" in this
> > > > case until the bridge stops seeing its own STP messages?
> > > At least this will not solve the more general problem of a 
> > > unidirectional link (rx working and tx broken).
> > 
> > hmm, if TX is broken there won't be a loop anyway?
> > 
> > Anyhow, even if my proposed change doesn't solve all cases it seems like
> > a useful, very simple, ad don to STP. I am just concerned that it can
> > break some other aspect of STP. So far it seems OK.
> > 
> > What is the bridge maintainers view on this?
> 
> Stephen, whats is your view about extending the bridge code according to
> above? Also, after looking at the bride code I don't see where this
> should be added, I must be getting old :(
> 
>         Jocke

If you want to make STP vlan aware, then fine, a good place to start
is getting a version of new RSTP and making it vlan aware.