netdev - Re: [Patch net] bridge: do not expire mdb entry when bridge still uses it

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Message-ID: <20130308040853.GA27704@gondor.apana.org.au>
Date:	Fri, 8 Mar 2013 12:08:53 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Cong Wang <amwang@...hat.com>
Cc:	netdev@...r.kernel.org, bridge@...ts.linux-foundation.org,
	Stephen Hemminger <stephen@...workplumber.org>,
	"David S. Miller" <davem@...emloft.net>,
	Adam Baker <linux@...er-net.org.uk>
Subject: Re: [Patch net] bridge: do not expire mdb entry when bridge still
 uses it

On Fri, Mar 08, 2013 at 12:06:53PM +0800, Cong Wang wrote:
> On Fri, 2013-03-08 at 10:47 +0800, Herbert Xu wrote:
> > On Fri, Mar 08, 2013 at 10:44:06AM +0800, Cong Wang wrote:
> > >
> > > This is a good question. It is due to inside br_handle_frame_finish() we
> > > use 'skb2' to decide if we deliver packets to bridge itself, and in this
> > > case 'skb2' is non-NULL only when:
> > > 
> > >                 if (mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) {
> > >                         if ((mdst && mdst->mglist) ||
> > >                             br_multicast_is_router(br))
> > >                                 skb2 = skb; //        <======== HERE
> > >                         br_multicast_forward(mdst, skb, skb2);
> > > 
> > > For other ports, br_multicast_forward() will always forward 'skb' to
> > > them.
> > 
> > Yes but the point is that other ports should also expire after the
> > timeout and thus be removed from mdst.  So why is this only happening
> > for the bridge aka mdst->mglist?
> 
> The mdst may be removed, however the BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)
> is still set, because in br_multicast_ipv4_rcv():

But those packets are only meant for routers, which is why we
have the br_multicast_is_router test above.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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