netdev - Re: [PATCH 2/3] bridge: trigger a bridge calculation upon port changes

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Message-ID: <20140318212243.GD28471@garbanzo.do-not-panic.com>
Date:	Tue, 18 Mar 2014 14:22:43 -0700
From:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>
To:	Cong Wang <cwang@...pensource.com>
Cc:	"Luis R. Rodriguez" <mcgrof@...e.com>,
	netdev <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	kvm@...r.kernel.org, xen-devel@...ts.xenproject.org,
	Stephen Hemminger <stephen@...workplumber.org>,
	bridge@...ts.linux-foundation.org
Subject: Re: [PATCH 2/3] bridge: trigger a bridge calculation upon port
 changes

On Tue, Mar 18, 2014 at 01:46:49PM -0700, Cong Wang wrote:
> On Fri, Mar 14, 2014 at 6:39 PM, Luis R. Rodriguez <mcgrof@...e.com> wrote:
> > On Thu, Mar 13, 2014 at 11:26:25AM -0700, Cong Wang wrote:
> >> On Wed, Mar 12, 2014 at 8:15 PM, Luis R. Rodriguez
> >> <mcgrof@...not-panic.com> wrote:
> >> >                         spin_unlock_bh(&p->br->lock);
> >> > +                       if (changed)
> >> > +                               call_netdevice_notifiers(NETDEV_CHANGEADDR,
> >> > +                                                        p->br->dev);
> >> > +                       netdev_update_features(p->br->dev);
> >>
> >> I think this is supposed to be in netdev event handler of br->dev
> >> instead of here.
> >
> > Do you mean netdev_update_features() ? I mimic'd what was being done on
> > br_del_if() given that root blocking is doing something similar. If
> > we need to change something for the above then I suppose it means we need
> > to change br_del_if() too. Let me know if you see any reason for something
> > else.
> >
> 
> Yeah, for me it looks like it's better to call netdev_update_features()
> in the event handler of br->dev, rather than where calling
> call_netdevice_notifiers(..., br->dev);.

I still don't see why, in fact trying to verify this I am wondering now
if instead we should actually fix br_features_recompute() to take into
consideration BR_ROOT_BLOCK as below. Notice how netdev_update_features()
is called above even if the MAC address did not change, just as is done
on br_del_if(). There is an NETDEV_FEAT_CHANGE event so would it be more
appropriate we just call

call_netdevice_notifiers(NETDEV_FEAT_CHANGE, p->br->dev)

for both the above then and also br_del_if()? How about the below
change?

diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
index 54d207d..dcd9378 100644
--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c
@@ -315,6 +315,8 @@ netdev_features_t br_features_recompute(struct net_bridge *br,
 	features &= ~NETIF_F_ONE_FOR_ALL;
 
 	list_for_each_entry(p, &br->port_list, list) {
+		if (p->flags & BR_ROOT_BLOCK)
+			continue;
 		features = netdev_increment_features(features,
 						     p->dev->features, mask);
 	}

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