[PATCH net-next] bridge: change the order of actions in addif/delif

[PATCH net-next] bridge: change the order of actions in addif/delif

[Hong Zhiguo]

From: Hong Zhiguo <zhiguohong@tencent.com>

netdev_rx_handler_register turns on the bridge traffic. It should
be the last action of br_add_if, after the installation of fdb and
stp staff. _Maybe_ traffic coming in before preparation of fdb and
stp is taken care of, but we could make it easier.

Vise versa, netdev_rx_handler_unregister actually turns off bridge
traffic from the dev. It should be the first action of br_del_if,
before fdb and stp staff is uninstalled.

Signed-off-by: Hong Zhiguo <zhiguohong@tencent.com>
---
 net/bridge/br_if.c | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
index c41d5fb..6544154 100644
--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c
@@ -133,6 +133,8 @@ static void del_nbp(struct net_bridge_port *p)
 
 	sysfs_remove_link(br->ifobj, p->dev->name);
 
+	netdev_rx_handler_unregister(dev);
+
 	dev_set_promiscuity(dev, -1);
 
 	spin_lock_bh(&br->lock);
@@ -148,8 +150,6 @@ static void del_nbp(struct net_bridge_port *p)
 
 	dev->priv_flags &= ~IFF_BRIDGE_PORT;
 
-	netdev_rx_handler_unregister(dev);
-
 	netdev_upper_dev_unlink(dev, br->dev);
 
 	br_multicast_del_port(p);
@@ -336,8 +336,8 @@ int br_add_if(struct net_bridge *br, struct net_device *dev)
 	if (dev->netdev_ops->ndo_start_xmit == br_dev_xmit)
 		return -ELOOP;
 
-	/* Device is already being bridged */
-	if (br_port_exists(dev))
+	/* Device is already being bridged or registered with other handler */
+	if (br_port_exists(dev) || dev->rx_handler)
 		return -EBUSY;
 
 	/* No bridging devices that dislike that (e.g. wireless) */
@@ -371,10 +371,6 @@ int br_add_if(struct net_bridge *br, struct net_device *dev)
 	if (err)
 		goto err4;
 
-	err = netdev_rx_handler_register(dev, br_handle_frame, p);
-	if (err)
-		goto err5;
-
 	dev->priv_flags |= IFF_BRIDGE_PORT;
 
 	dev_disable_lro(dev);
@@ -394,8 +390,6 @@ int br_add_if(struct net_bridge *br, struct net_device *dev)
 		br_stp_enable_port(p);
 	spin_unlock_bh(&br->lock);
 
-	br_ifinfo_notify(RTM_NEWLINK, p);
-
 	if (changed_addr)
 		call_netdevice_notifiers(NETDEV_CHANGEADDR, br->dev);
 
@@ -404,12 +398,14 @@ int br_add_if(struct net_bridge *br, struct net_device *dev)
 	if (br_fdb_insert(br, p, dev->dev_addr, 0))
 		netdev_err(dev, "failed insert local address bridge forwarding table\n");
 
+	/* rx_handler is already tested, no fail here */
+	netdev_rx_handler_register(dev, br_handle_frame, p);
+
+	br_ifinfo_notify(RTM_NEWLINK, p);
 	kobject_uevent(&p->kobj, KOBJ_ADD);
 
 	return 0;
 
-err5:
-	netdev_upper_dev_unlink(dev, br->dev);
 err4:
 	br_netpoll_disable(p);
 err3:
-- 
1.8.1.2

Re: [PATCH net-next] bridge: change the order of actions in addif/delif

[Eric Dumazet]

On Tue, 2013-09-17 at 15:44 +0800, Hong Zhiguo wrote:
> From: Hong Zhiguo <zhiguohong@tencent.com>
> 
> netdev_rx_handler_register turns on the bridge traffic. It should
> be the last action of br_add_if, after the installation of fdb and
> stp staff. _Maybe_ traffic coming in before preparation of fdb and
> stp is taken care of, but we could make it easier.
> 
> Vise versa, netdev_rx_handler_unregister actually turns off bridge
> traffic from the dev. It should be the first action of br_del_if,
> before fdb and stp staff is uninstalled.
> 
> Signed-off-by: Hong Zhiguo <zhiguohong@tencent.com>
> ---
>  net/bridge/br_if.c | 20 ++++++++------------
>  1 file changed, 8 insertions(+), 12 deletions(-)
> 
> diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
> index c41d5fb..6544154 100644
> --- a/net/bridge/br_if.c
> +++ b/net/bridge/br_if.c
> @@ -133,6 +133,8 @@ static void del_nbp(struct net_bridge_port *p)
>  
>  	sysfs_remove_link(br->ifobj, p->dev->name);
>  
> +	netdev_rx_handler_unregister(dev);
> +
>  	dev_set_promiscuity(dev, -1);
>  
>  	spin_lock_bh(&br->lock);
> @@ -148,8 +150,6 @@ static void del_nbp(struct net_bridge_port *p)
>  
>  	dev->priv_flags &= ~IFF_BRIDGE_PORT;
>  
> -	netdev_rx_handler_unregister(dev);
> -
>  	netdev_upper_dev_unlink(dev, br->dev);
>  

This was really your first patch, and I 'Acked' it.
(OK, changelog can be different now we fixed the bug)

The following should be part of a different patch

>  	br_multicast_del_port(p);
> @@ -336,8 +336,8 @@ int br_add_if(struct net_bridge *br, struct net_device *dev)
>  	if (dev->netdev_ops->ndo_start_xmit == br_dev_xmit)
>  		return -ELOOP;
>  
> -	/* Device is already being bridged */
> -	if (br_port_exists(dev))
> +	/* Device is already being bridged or registered with other handler */
> +	if (br_port_exists(dev) || dev->rx_handler)
>  		return -EBUSY;

rcu_access_pointer(dev->rx_handler)

Anyway, this is risky, because it assumes netdev_rx_handler_register()
implementation wont change.

Just leave the code as is, I don't think its worth it.

Re: [PATCH net-next] bridge: change the order of actions in addif/delif

[Stephen Hemminger]

On Tue, 17 Sep 2013 15:44:43 +0800
Hong Zhiguo <honkiko@gmail.com> wrote:

> -	/* Device is already being bridged */
> -	if (br_port_exists(dev))
> +	/* Device is already being bridged or registered with other handler */
> +	if (br_port_exists(dev) || dev->rx_handler)
>  		return -EBUSY;

Direct access to dev->rx_handler should be avoided.
The error check should be in netdev_rx_handler_register.