netdev - Re: [PATCH v2 net 1/3] net: dsa: only unset VLAN filtering when last port leaves last VLAN-aware bridge

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Message-ID: <87lfafm5xh.fsf@waldekranz.com>
Date:   Mon, 22 Mar 2021 18:52:58 +0100
From:   Tobias Waldekranz <tobias@...dekranz.com>
To:     Vladimir Oltean <olteanv@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: Re: [PATCH v2 net 1/3] net: dsa: only unset VLAN filtering when last port leaves last VLAN-aware bridge

On Sun, Mar 21, 2021 at 00:59, Vladimir Oltean <olteanv@...il.com> wrote:
> From: Vladimir Oltean <vladimir.oltean@....com>
>
> 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 <vladimir.oltean@....com>
> Tested-by: Florian Fainelli <f.fainelli@...il.com>
> Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>  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..32963276452f 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 leaves the last
> +	 * VLAN-aware bridge.
>  	 */
>  	if (unset_vlan_filtering && ds->vlan_filtering_is_global) {
> -		for (i = 0; i < ds->num_ports; i++) {
> -			if (i == info->port)
> -				continue;
> -			if (dsa_to_port(ds, i)->bridge_dev == info->br) {
> +		for (port = 0; port < ds->num_ports; port++) {
> +			struct net_device *bridge_dev;
> +
> +			bridge_dev = dsa_to_port(ds, port)->bridge_dev;
> +
> +			if (bridge_dev && br_vlan_enabled(bridge_dev)) {
>  				unset_vlan_filtering = false;
>  				break;
>  			}
> -- 
> 2.25.1

Is it the case that all devices in which VLAN filtering is a global
setting are also single-chip? To my _D_SA eyes, it feels like we should
have to iterate over all ports in the tree, not just the switch.