Subject: Re: [PATCH net] net: dsa: only unset VLAN filtering when last port leaves last VLAN-aware bridge

From: Kurt Kanzenbach <[email-masked]>
Date: Tue, 09 Mar 2021 07:31:25 +0100

Hi Vladimir,

On Mon Mar 08 2021, Vladimir Oltean wrote:
> From: Vladimir Oltean <[email-masked]>
>
> DSA is aware of switches with global VLAN filtering since the blamed
> commit, but it makes a bad decision when multiple bridges are spanning
> the same switch:
>
> ip link add br0 type bridge vlan_filtering 1
> ip link add br1 type bridge vlan_filtering 1
> ip link set swp2 master br0
> ip link set swp3 master br0
> ip link set swp4 master br1
> ip link set swp5 master br1
> ip link set swp5 nomaster
> ip link set swp4 nomaster
> [138665.939930] sja1105 spi0.1: port 3: dsa_core: VLAN filtering is a global setting
> [138665.947514] DSA: failed to notify DSA_NOTIFIER_BRIDGE_LEAVE
>
> When all ports leave br1, DSA blindly attempts to disable VLAN filtering
> on the switch, ignoring the fact that br0 still exists and is VLAN-aware
> too. It fails while doing that.
>
> This patch checks whether any port exists at all and is under a
> VLAN-aware bridge.
>
> Fixes: d371b7c92d19 ("net: dsa: Unset vlan_filtering when ports leave the bridge")
> Signed-off-by: Vladimir Oltean <[email-masked]>

Code looks correct. One comment below.

> ---
>  net/dsa/switch.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/net/dsa/switch.c b/net/dsa/switch.c
> index 4b5da89dc27a..56ed31b0e636 100644
> --- a/net/dsa/switch.c
> +++ b/net/dsa/switch.c
> @@ -107,7 +107,7 @@ static int dsa_switch_bridge_leave(struct dsa_switch *ds,
>  	bool unset_vlan_filtering = br_vlan_enabled(info->br);
>  	struct dsa_switch_tree *dst = ds->dst;
>  	struct netlink_ext_ack extack = {0};
> -	int err, i;
> +	int err, port;
>  
>  	if (dst->index == info->tree_index && ds->index == info->sw_index &&
>  	    ds->ops->port_bridge_join)
> @@ -124,13 +124,16 @@ static int dsa_switch_bridge_leave(struct dsa_switch *ds,
>  	 * it. That is a good thing, because that lets us handle it and also
>  	 * handle the case where the switch's vlan_filtering setting is global
>  	 * (not per port). When that happens, the correct moment to trigger the
> -	 * vlan_filtering callback is only when the last port left this bridge.
> +	 * vlan_filtering callback is only when the last port the last

Somehow "left" got missing. Shouldn't that line be:

"vlan_filtering callback is only when the last port left the last" ?

> +	 * VLAN-aware bridge.
>  	 */

Thanks,
Kurt