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

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Message-ID: <20110628160018.GC126252@jupiter.n2.diac24.net>
Date:	Tue, 28 Jun 2011 18:00:18 +0200
From:	David Lamparter <equinox@...c24.net>
To:	Stephen Hemminger <shemminger@...ux-foundation.org>
Cc:	David Lamparter <equinox@...c24.net>,
	Nick Carter <ncarter100@...il.com>, netdev@...r.kernel.org,
	davem@...emloft.net
Subject: Re: [PATCH] bridge: Forward EAPOL Kconfig option BRIDGE_PAE_FORWARD

On Tue, Jun 28, 2011 at 08:10:15AM -0700, Stephen Hemminger wrote:
> On Tue, 28 Jun 2011 17:02:57 +0200
> David Lamparter <equinox@...c24.net> wrote:
> > >  	if (skb) {
> > > +		/* Prevent Crosstalk where a Supplicant on one Port attempts to
> > > +		 * interfere with authentications occurring on another Port.
> > > +		 * (IEEE Std 802.1X-2001 C.3.3)
> > > +		 */
> > > +		if (unlikely(!br->pae_forward &&
> > > +		    skb->protocol == htons(ETH_P_PAE)))
> > 
> > No, please don't.
> > 
> > Linux bridging has two "grand" modes: dumb and STP enabled.
> > 
> > If we're running a dumb bridge, we behave like an ethernet hub without
> > any intelligence, and in that case we should absolutely forward 802.1X
> > frames. We may have (e.g. VM) client(s) that want to authenticate with a
> > physical switch.
> > (For the spec, this counts as "repeater", not "bridge"/"switch")
> > 
> > If we're running with STP enabled, then 802.1X traffic should already be
> > caught by the general ethernet link-local multicast drop (which applies
> > to 01:80:c2:/24 and therefore catches 802.1X too.)
> 
> The problem is that STP is not enabled by default, and most people don't
> know how to enable it.

Yes, the default is a dumb hub (IMHO correctly so). And a dumb hub will
forward 802.1X packets (IMHO also correctly so).

Why should we specifically add a knob for EAPOL? Next we're adding one
for STP itself, then one for LLDP, then one for Cisco's deprecated
crap (CDP, DTP, ...) etc.

If you want a dumb hub that drops EAPOL, use ebtables.

-David

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