[Rstplib-users] Issue when change of topologie

[Olivier J. <oj...@ek...>]

Hi

I have integrated recently the RSTP daemon in our product. (equipement 1 & 2)

We have an issue with this change of topology :


0. The Root is in LAN
-----------------|                       |------------------|_D___________R__|------------------|
LAN               |____________| equipement 1 |                                | equipement 2 | 
-----------------|                   R |------------------|_D___________ A_|------------------|

If i unplug the ethernet cable between equiment 1 & LAN (It's an undirect link failure)

I have this sequence
1. Timer Max_age ends, so  equipement 1 becomes root

The Root is in LAN
-----------------|                       |------------------|_D_ _________ D_|------------------|
LAN               |                       | equipement 1 |                                | equipement 2 | 
-----------------|                      |------------------|_D_  _________ R_|------------------|

2. equipement 2 accepts this change and declares itself as the new root because it has the smallest Mac address


-----------------|                       |------------------|_A_ __________D_|------------------|
LAN               |                       | equipement 1 |                                 | equipement 2 | 
-----------------|                      |------------------|_R_  _________ D_|------------------|


 2 new  elections are done between step 1 & 2, but for a time a loop is created between the 2 cables between equipement 1 & 2:

The reason: the state machine of roletrns.c goes directly from  LEARNING state to  DESIGNATED_FORWARD 
at the line 402 we have 
      if ((!port->fdWhile  || port->agreed || port->operEdge) &&
          (!port->rrWhile  || !port->reRoot) &&
          !port->sync &&
          (port->learn && !port->forward)) {
        return STP_hop_2_state (this, DESIGNATED_FORWARD);

the port->agreed has the value 1 so we don't wait the timer fdWhile, and the port goes too early into state forwarding

What do you think about my issue?

Thanks

Olivier