netdev - Re: [net-next,v5,2/3] bridge: only expire the mdb entry when query is received

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Date:	Fri, 21 Jun 2013 15:31:41 +0800
From:	Cong Wang <amwang@...hat.com>
To:	Herbert Xu <herbert@...dor.hengli.com.au>
Cc:	Linus Lüssing <linus.luessing@....de>,
	netdev@...r.kernel.org,
	Stephen Hemminger <stephen@...workplumber.org>,
	"David S. Miller" <davem@...emloft.net>,
	Adam Baker <linux@...er-net.org.uk>
Subject: Re: [net-next,v5,2/3] bridge: only expire the mdb entry when query
 is received

On Wed, 2013-06-19 at 12:44 +0800, Herbert Xu wrote:
> On Tue, Jun 18, 2013 at 02:03:38PM +0200, Linus Lüssing wrote:
> > Hi Amerigo,
> > 
> > I just tested these three patches on top of 3.10-rc6 (thanks for
> > looking into these issues so far!) but unfortunately I'm still
> > having problems if there is no querier on the link:
> > 
> > We will never discover a multicast listener which sends its
> > startup MLD reports before being attached to the bridge port.
> > 
> > I had reported that issue two months ago to Herbert's patch which
> > changed the querier default [1].
> > 
> > I guess in such a scenario where neither our querier is activated
> > nor could we detect any querier, then the only safe thing we can
> > do is to disable the bridge multicast snooping, isn't it?
> 
> If we have seen no queries then we should simply flood.  The fact
> that we don't currently is a bug.

Something like this?

diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index 1b8b8b8..df49d14 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -105,6 +105,10 @@ int br_handle_frame_finish(struct sk_buff *skb)
                        if ((mdst && mdst->mglist) ||
                            br_multicast_is_router(br))
                                skb2 = skb;
+                       else if (hlist_empty(&br->router_list)) {
+                               unicast = false;
+                               goto flood;
+                       }
                        br_multicast_forward(mdst, skb, skb2);
                        skb = NULL;
                        if (!skb2)
@@ -121,6 +125,7 @@ int br_handle_frame_finish(struct sk_buff *skb)
                skb = NULL;
        }
 
+flood:
        if (skb) {
                if (dst) {
                        dst->used = jiffies;

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