netdev - Re: [PATCH 2/2] bridge: pass through 802.1X & co. in 'dumb' mode

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Date:	Wed, 29 Jun 2011 23:56:18 +0100
From:	Nick Carter <ncarter100@...il.com>
To:	David Lamparter <equinox@...c24.net>
Cc:	netdev@...r.kernel.org,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	davem@...emloft.net
Subject: Re: [PATCH 2/2] bridge: pass through 802.1X & co. in 'dumb' mode

On 28 June 2011 23:03, David Lamparter <equinox@...c24.net> wrote:
> when operating without STP, we're a dumb switch and should be able to
> forward ethernet management protocols like 802.1X, LLDP and GVRP.
I don't like the idea of tying STP on / off with the forwarding of
these other protocols.  These other protocols are not dependent on
STP.  These diffs change the default behaviour so that if someone
writes an 802.1X authenticator in userspace then all deployments will
have to turn STP on to be able to use it !!

If I was a sysadmin and I configured 'bridge_stp off' in say
/etc/interfaces, i would be very surprised and alarmed to find I had
turned *on* forwarding a load of protocols.

Also many of these addresses are reserved for future use.  Do we
really want to forward them before we know what they will be used for
?
Nick
>
> if this is not desired, it can be enacted as local policy through
> ebtables.
>
> if we're in STP mode we basically claim to be an intelligent switch and
> should implement these protocols properly (in userspace).
>
> Signed-off-by: David Lamparter <equinox@...c24.net>
> ---
> compile-tested only
>
>  net/bridge/br_input.c |    9 ++++++---
>  1 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
> index c873db5..4cee1b5 100644
> --- a/net/bridge/br_input.c
> +++ b/net/bridge/br_input.c
> @@ -167,16 +167,19 @@ rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
>                if (dest[5] == 0x01 || dest[5] == 0x02)
>                        return RX_HANDLER_PASS;
>
> -               /* If STP is turned off, then forward */
> -               if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0)
> +               /* If STP is turned off, we're a dumb switch and therefore
> +                * forward the remaining link-locals. (STP, 802.1X, LLDP,
> +                * GVRP & co.) */
> +               if (p->br->stp_enabled == BR_NO_STP)
>                        goto forward;
>
>                if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
>                            NULL, br_handle_local_finish)) {
>                        return RX_HANDLER_CONSUMED; /* consumed by filter */
>                } else {
> +                       /* stay on physdev for userspace implementation */
>                        *pskb = skb;
> -                       return RX_HANDLER_PASS; /* continue processing */
> +                       return RX_HANDLER_PASS;
>                }
>        }
>
> --
> 1.7.5.3
>
>
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