netdev - Re: [PATCH] bridge: Forward EAPOL Kconfig option BRIDGE_PAE

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Date:	Tue, 28 Jun 2011 22:22:00 +0200
From:	David Lamparter <equinox@...c24.net>
To:	Nick Carter <ncarter100@...il.com>
Cc:	David Lamparter <equinox@...c24.net>,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [PATCH] bridge: Forward EAPOL Kconfig option BRIDGE_PAE_FORWARD

On Tue, Jun 28, 2011 at 09:00:16PM +0100, Nick Carter wrote:
> >>                 /* If STP is turned off, then forward */
> >> -               if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0)
> >> +               if (p->br->stp_enabled == BR_NO_STP &&
> >> +                       (dest[5] == 0 || skb->protocol == htons(ETH_P_PAE)))
> >>                         goto forward;
> >> Nick
> >
> > That code actually looks quite wrong to me, we should be forwarding all of
> > the 01:80:C2:00:00:0x groups in non-STP mode, especially :0E and :0D.
> > (LLDP and GVRP/MVRP)
> >
> > Pause frames are the one exception that makes the rule, but as the
> > comment a few lines above states, "Pause frames shouldn't be passed up by
> > driver anyway".
> >
> > Btw, what might make sense is a general knob for forwarding those
> > link-local groups, split off from the STP switch so the STP switch
> > controls only the :00 (STP) group. That way you can decide separately
> > whether you want to be LLDP/GVRP/802.1X/... transparent and whether you
> > want to run STP.
> 
> Sounds good to me.  So we go for :03, :0D, and :0E.  We cant touch :02 see:
>  commit f01cb5fbea1c1613621f9f32f385e12c1a29dde0
>  Revert "bridge: Forward reserved group addresses if !STP"
> 
> > Not sure if it's needed, it can always be done with ebtables...
> What would be the ebtables rules to achieve the forwarding of :03 ?  I
> asked this question on the netfilter list and the only response I got
> said ebtables was a filter and could not do this. :03 is hitting
> NF_BR_LOCAL_IN.  How would you 'reinject' it so it is forwarded ?

'reinject' isn't possible when it hits that code path - which is pretty
much why I'm saying we should be forwarding everything in the non-STP
case.

I have to read up on the bonding interactions, but to my understanding
the only reasonable usage case is to have the bond below the bridge like
 eth0 \
      |- bond0 - br0
 eth1 /
then the bonding should receive (and consume) the packets before they
reach the bridge.

(Some quick googling reveals that hardware switch chips special-drop
01:80:c2:00:00:01 [802.3x/pause] and :02 [802.3ad/lacp] and nothing
else - for the dumb ones anyway. It also seems like the match for pause
frames usually works on the address, not on the protocol field like we
do it...)


-David

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