Linux Ethernet Bridging - Oct 2010 - [Bridge] Invalid BPDU transmission?

Hello,

in function STP_transmit_check_conditions (rstplib/transmit.c) the
case:

    case IDLE:
      if (!port->helloWhen) return STP_hop_2_state (this,
      TRANSMIT_PERIODIC);
      if (!port->sendRSTP && port->newInfo &&
          (port->txCount < TxHoldCount) &&
          (port->role == DesignatedPort) &&
          port->helloWhen)
        return STP_hop_2_state (this, TRANSMIT_CONFIG);
      if (!port->sendRSTP && port->newInfo &&
          (port->txCount < TxHoldCount) &&
          (port->role == RootPort) &&
          port->helloWhen)
        return STP_hop_2_state (this, TRANSMIT_TCN);
      if (port->sendRSTP && port->newInfo &&
          (port->txCount < TxHoldCount) &&
          ((port->role == RootPort) ||         <----
           (port->role == DesignatedPort)))
        return STP_hop_2_state (this, TRANSMIT_RSTP);
      break;

states that a RSTP bpdu can be transmitted even throught a RootPort
which, IMHO, is not correct... only topology change BPDU should be
sent over the RootPort. That's why I suggest to remove the line with
the arrow (<----).

Comments? :)

Ciao,

Rodolfo

-- 

GNU/Linux Solutions                  e-mail: giometti at enneenne.com
Linux Device Driver                          giometti at linux.it
Embedded Systems                     phone:  +39 349 2432127
UNIX programming                     skype:  rodolfo.giometti
Freelance ICT Italia - Consulente ICT Italia - www.consulenti-ict.it

Both CONFIG and TCN BPDUs are used only in STP compatibility mode. In
RSTP mode, the BPDUs sent in both directions are RSTP BPDUs. So they
can be sent on the root port.

For a description of how topology changes are handled, see the section
titled "New Topology Change Mechanisms" in
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml

Is this causing any particular issue?

On Tue, Oct 5, 2010 at 3:24 PM, Rodolfo Giometti <giometti at
enneenne.com> wrote:
> Hello,
>
> in function STP_transmit_check_conditions (rstplib/transmit.c) the
> case:
>
> ? ?case IDLE:
> ? ? ?if (!port->helloWhen) return STP_hop_2_state (this,
> ? ? ?TRANSMIT_PERIODIC);
> ? ? ?if (!port->sendRSTP && port->newInfo &&
> ? ? ? ? ?(port->txCount < TxHoldCount) &&
> ? ? ? ? ?(port->role == DesignatedPort) &&
> ? ? ? ? ?port->helloWhen)
> ? ? ? ?return STP_hop_2_state (this, TRANSMIT_CONFIG);
> ? ? ?if (!port->sendRSTP && port->newInfo &&
> ? ? ? ? ?(port->txCount < TxHoldCount) &&
> ? ? ? ? ?(port->role == RootPort) &&
> ? ? ? ? ?port->helloWhen)
> ? ? ? ?return STP_hop_2_state (this, TRANSMIT_TCN);
> ? ? ?if (port->sendRSTP && port->newInfo &&
> ? ? ? ? ?(port->txCount < TxHoldCount) &&
> ? ? ? ? ?((port->role == RootPort) || ? ? ? ? <----
> ? ? ? ? ? (port->role == DesignatedPort)))
> ? ? ? ?return STP_hop_2_state (this, TRANSMIT_RSTP);
> ? ? ?break;
>
> states that a RSTP bpdu can be transmitted even throught a RootPort
> which, IMHO, is not correct... only topology change BPDU should be
> sent over the RootPort. That's why I suggest to remove the line with
> the arrow (<----).
>
> Comments? :)
>
> Ciao,
>
> Rodolfo
>
> --
>
> GNU/Linux Solutions ? ? ? ? ? ? ? ? ?e-mail: giometti at enneenne.com
> Linux Device Driver ? ? ? ? ? ? ? ? ? ? ? ? ?giometti at linux.it
> Embedded Systems ? ? ? ? ? ? ? ? ? ? phone: ?+39 349 2432127
> UNIX programming ? ? ? ? ? ? ? ? ? ? skype: ?rodolfo.giometti
> Freelance ICT Italia - Consulente ICT Italia - www.consulenti-ict.it
> _______________________________________________
> Bridge mailing list
> Bridge at lists.linux-foundation.org
> https://lists.linux-foundation.org/mailman/listinfo/bridge
>

> Sorry, the correct BDPU is the following:
>
> 01 80 c2 00 00 00 00 01 ?f4 33 1c 54 00 27 42 42
> 03 00 00 02 02 7e 00 00 ?00 01 f4 7e a2 57 00 00
> 00 00 00 00 00 01 f4 7e ?a2 57 83 4e 00 00 0a 00
> 01 00 0f 00 00
The 7e in 00 00 02 02 7e ... is a flags value with the proposal flag
set (mask 0x02), so it seems correct that the test bridge should
respond with agreement flag set (mask 0x40).