Subject: Re: [PATCH] bridge: control carrier based on ports online

From: Stephen Hemminger <[email-masked]>
Date: Mon, 7 Mar 2011 13:44:50 -0800

On Mon, 07 Mar 2011 21:48:16 +0100
Nicolas de Pesloüan <[email-masked]> wrote:

> Le 07/03/2011 19:34, Stephen Hemminger a écrit :
> > This makes the bridge device behave like a physical device.
> > In earlier releases the bridge always asserted carrier. This
> > changes the behavior so that bridge device carrier is on only
> > if one or more ports are in the forwarding state. This
> > should help IPv6 autoconfiguration, DHCP, and routing daemons.
> >
> > I did brief testing with Network and Virt manager and they
> > seem fine, but since this changes behavior of bridge, it should
> > wait until net-next (2.6.39).
> >
> > Signed-off-by: Stephen Hemminger<[email-masked]>
> >
> > ---
> >   net/bridge/br_device.c    |    4 ++++
> >   net/bridge/br_stp.c       |   35 ++++++++++++++++++++++-------------
> >   net/bridge/br_stp_timer.c |    1 +
> >   3 files changed, 27 insertions(+), 13 deletions(-)
> >
> > --- a/net/bridge/br_device.c	2011-03-07 08:40:08.913599513 -0800
> > +++ b/net/bridge/br_device.c	2011-03-07 08:40:48.382377389 -0800
> > @@ -78,6 +78,8 @@ static int br_dev_open(struct net_device
> >   {
> >   	struct net_bridge *br = netdev_priv(dev);
> >
> > +	netif_carrier_off(dev);
> > +
> >   	br_features_recompute(br);
> >   	netif_start_queue(dev);
> >   	br_stp_enable_bridge(br);
> > @@ -94,6 +96,8 @@ static int br_dev_stop(struct net_device
> >   {
> >   	struct net_bridge *br = netdev_priv(dev);
> >
> > +	netif_carrier_off(dev);
> > +
> >   	br_stp_disable_bridge(br);
> >   	br_multicast_stop(br);
> >
> > --- a/net/bridge/br_stp.c	2011-03-07 08:41:58.619783678 -0800
> > +++ b/net/bridge/br_stp.c	2011-03-07 08:53:58.953558810 -0800
> > @@ -397,28 +397,37 @@ static void br_make_forwarding(struct ne
> >   void br_port_state_selection(struct net_bridge *br)
> >   {
> >   	struct net_bridge_port *p;
> > +	unsigned int liveports = 0;
> >
> >   	/* Don't change port states if userspace is handling STP */
> >   	if (br->stp_enabled == BR_USER_STP)
> >   		return;
> >
> >   	list_for_each_entry(p,&br->port_list, list) {
> > -		if (p->state != BR_STATE_DISABLED) {
> > -			if (p->port_no == br->root_port) {
> > -				p->config_pending = 0;
> > -				p->topology_change_ack = 0;
> > -				br_make_forwarding(p);
> > -			} else if (br_is_designated_port(p)) {
> > -				del_timer(&p->message_age_timer);
> > -				br_make_forwarding(p);
> > -			} else {
> > -				p->config_pending = 0;
> > -				p->topology_change_ack = 0;
> > -				br_make_blocking(p);
> > -			}
> > +		if (p->state == BR_STATE_DISABLED)
> > +			continue;
> > +
> > +		if (p->port_no == br->root_port) {
> > +			p->config_pending = 0;
> > +			p->topology_change_ack = 0;
> > +			br_make_forwarding(p);
> > +		} else if (br_is_designated_port(p)) {
> > +			del_timer(&p->message_age_timer);
> > +			br_make_forwarding(p);
> > +		} else {
> > +			p->config_pending = 0;
> > +			p->topology_change_ack = 0;
> > +			br_make_blocking(p);
> 
> Is the above part really related to the purpose of this patch? It looks like (good) cleanup, but 
> should be in a different patch.
> 
> Except from this comment,
> 
> Reviewed-by: Nicolas de Pesloüan <[email-masked]>

The loop is going over the state of ports.
Since the new code at the end of loop has to check for STATE_FORWARDING
it is clearer with continue statement.  When adding code it is always
better to clarify the logic in the process rather than making it
more complex.

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