Subject: Re: [patch net-next 0/4] net: allow to change carrier from userspace

From: Stephen Hemminger <[email-masked]>
Date: Fri, 14 Dec 2012 09:23:43 -0800

On Fri, 14 Dec 2012 18:13:45 +0100
Jiri Pirko <[email-masked]> wrote:

> Fri, Dec 14, 2012 at 05:59:18PM CET, [email-masked] wrote:
> >On Fri, 14 Dec 2012 17:35:32 +0100
> >Jiri Pirko <[email-masked]> wrote:
> >
> >> Fri, Dec 14, 2012 at 05:12:01PM CET, [email-masked] wrote:
> >> >On Fri, 14 Dec 2012 15:41:34 +0100
> >> >Jiri Pirko <[email-masked]> wrote:
> >> >
> >> >> Thu, Dec 13, 2012 at 07:20:51PM CET, [email-masked] wrote:
> >> >> >On Thu, 13 Dec 2012 16:17:33 -0200
> >> >> >Flavio Leitner <[email-masked]> wrote:
> >> >> >
> >> >> >> On Thu, 13 Dec 2012 10:09:33 -0800
> >> >> >> Stephen Hemminger <[email-masked]> wrote:
> >> >> >> 
> >> >> >> > On Thu, 13 Dec 2012 15:54:23 -0200
> >> >> >> > Flavio Leitner <[email-masked]> wrote:
> >> >> >> > 
> >> >> >> > > I am saying this because people are used to and there are scripts out
> >> >> >> > > there using something like:
> >> >> >> > > # ethtool <iface> | grep 'Link'
> >> >> >> > > to react an interface failure.
> >> >> >> > 
> >> >> >> > Then the script is broken. It is asking about hardware state.
> >> >> >> 
> >> >> >> I was talking about the team master interface, so it makes sense
> >> >> >> to check its 'hardware' state. Just think on 'bond0' interface
> >> >> >> with no slaves. It should report Link detected: no.
> >> >> >> 
> >> >> >> See bond_release(), what happens if bond->slave_cnt == 0, for instance.
> >> >> >> 
> >> >> >
> >> >> >I was thinking more that ethtool operation for reporting link on
> >> >> >the team device should use the proper check rather than just using netif_carrier_ok(),
> >> >> >the team ethtool operation for get_link should be check IFF_RUNNING flag
> >> >> >in dev->flags which is controlled by operstate transistions.
> >> >> 
> >> >> I admit I'm bit confused now.
> >> >> 
> >> >> For example in bridge code:
> >> >> in br_add_if() - netif_carrier_ok() is checked and by the value it is
> >> >> decided if br_stp_enable_port() is called or not. Wouldn't it make more
> >> >> sense to check IFF_RUNNING (or netif_oper_up()) here?
> >> >> 
> >> >> The reason I'm asing is that if team device is in bridge, carrier is
> >> >> always ON and I'm fiddling with IF_OPER_UP and IF_OPER_DORMANT from
> >> >> userspace, in current code, bridge wouldn't know the difference...
> >> >> 
> >> >> There are more exmaples of similar usage of netif_carrier_ok() in
> >> >> bridge (called on ports), bonding (called on slaves), team code (called on ports).
> >> >
> >> >Yes the bridge should be fixed to work with user controlled devices.
> >> 
> >> Okay. I'll try to figure out some patchset over the weekend.
> >> 
> >> Thanks.
> >> 
> >
> >Something like this seems needed.
> >
> >--- a/net/bridge/br_if.c	2012-10-25 09:11:15.627272524 -0700
> >+++ b/net/bridge/br_if.c	2012-12-14 08:58:14.329847361 -0800
> >@@ -66,14 +66,14 @@ void br_port_carrier_check(struct net_br
> > 	struct net_device *dev = p->dev;
> > 	struct net_bridge *br = p->br;
> > 
> >-	if (netif_running(dev) && netif_carrier_ok(dev))
> >+	if (netif_running(dev) && netif_oper_up(dev))
> > 		p->path_cost = port_cost(dev);
> > 
> > 	if (!netif_running(br->dev))
> > 		return;
> > 
> > 	spin_lock_bh(&br->lock);
> >-	if (netif_running(dev) && netif_carrier_ok(dev)) {
> >+	if (netif_running(dev) && netif_oper_up(dev))
> > 		if (p->state == BR_STATE_DISABLED)
> > 			br_stp_enable_port(p);
> > 	} else {
> >--- a/net/bridge/br_notify.c	2012-10-25 09:11:15.631272484 -0700
> >+++ b/net/bridge/br_notify.c	2012-12-14 08:57:36.954222724 -0800
> >@@ -82,7 +82,7 @@ static int br_device_event(struct notifi
> > 		break;
> > 
> > 	case NETDEV_UP:
> >-		if (netif_carrier_ok(dev) && (br->dev->flags & IFF_UP)) {
> >+		if (netif_running(br->dev) && netif_oper_up(dev)) {
> > 			spin_lock_bh(&br->lock);
> > 			br_stp_enable_port(p);
> > 			spin_unlock_bh(&br->lock);
> 
> 
> Yes. I have this already in my queue. I just spotted a problem though.
> 
> Lets say teamd sets operstate of the team device by values IF_OPER_UP
> and IF_OPER_DORMANT depending on teamd states of ports.
> What if one would like to use 802.1X supplicant on the same device?
> That would not be possible.
> 
> This proves that the layering would not be correct. It look like the
> carrier userspace set would be the correct thing to do after all...
> 
> What do you think?

That is tough, you have two applications conflicting over control of
the same state on the same device.