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: <20210322175615.47awcvac2sbxqqyc@skbuf>
Date:   Mon, 22 Mar 2021 19:56:15 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Tobias Waldekranz <tobias@...dekranz.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        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 Mon, Mar 22, 2021 at 06:52:58PM +0100, Tobias Waldekranz wrote:
> 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.

Correct, I might revisit this if I ever get my hands on a board with
sja1105 switches in a real multi-switch tree, and not in disjoint trees
as I have had access to so far.