[Bridge] STP bug, loop not detetcted

[Joakim Tjernlund]

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?

 Jocke