Re: [PATCH net] net: br: Fix igmp snooping offload with CONFIG_BRIDGE_VLAN_FILTERING

[Andrew Lunn]

On Tue, Oct 03, 2017 at 12:29:56PM +0900, Toshiaki Makita wrote:
> On 2017/10/03 9:55, Andrew Lunn wrote:
> > With CONFIG_BRIDGE_VLAN_FILTERING enabled, but the feature not enabled
> > via /sys/class/net/brX/bridge/vlan_filtering, mdb offloaded to the
> > kernel have the wrong VID.
> > 
> > When an interface is added to the bridge, switchdev is first used to
> > notify the hardware that a port has joined a bridge. This is
> > immediately followed by the default_pvid, 1, being added to the
> > interface via another switchdev call.
> > 
> > The bridge will then perform IGMP snooping, and offload an mdb entries
> > to the switch as needed. With vlan filtering disabled, the vid is left
> > as 0. This causes the switch to put the static mdb into the wrong
> > vlan, and so frames are not forwarded by the mdb entry.
> > 
> > If vlan filtering is disable, use the default_pvid, not 0.
> > 
> > Fixes: f1fecb1d10ec ("bridge: Reflect MDB entries to hardware")
> > Signed-off-by: Andrew Lunn <and...@lunn.ch>
> > ---
> >  net/bridge/br_vlan.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
> > index 233a30040c91..aa3589891797 100644
> > --- a/net/bridge/br_vlan.c
> > +++ b/net/bridge/br_vlan.c
> > @@ -492,6 +492,7 @@ bool br_allowed_ingress(const struct net_bridge *br,
> >      */
> >     if (!br->vlan_enabled) {
> >             BR_INPUT_SKB_CB(skb)->vlan_filtered = false;
> > +           *vid = br_get_pvid(vg);
> >             return true;
> >     }
> >  
> 
> This does not look correct.
> This will update fdb with vid which is not 0.
> Pvid can be different between each port even when vlan_filtering is
> disabled so unicast forwarding (fdb learning) will break.
> Also, fdb is visible to userspace so this can break userspace which
> expects fdb entries with 0 as well.
> 
> Why does the switch driver use pvid while vlan_filtering is disabled?

Hi Toshiaki

We get a vlan added to the port. I think it comes from a combination
of:


int br_vlan_init(struct net_bridge *br)
{
        struct net_bridge_vlan_group *vg;
        int ret = -ENOMEM;

        vg = kzalloc(sizeof(*vg), GFP_KERNEL);
        if (!vg)
                goto out;
        ret = rhashtable_init(&vg->vlan_hash, &br_vlan_rht_params);
        if (ret)
                goto err_rhtbl;
        ret = vlan_tunnel_init(vg);
        if (ret)
                goto err_tunnel_init;
        INIT_LIST_HEAD(&vg->vlan_list);
        br->vlan_proto = htons(ETH_P_8021Q);
        br->default_pvid = 1;

and

int nbp_vlan_init(struct net_bridge_port *p)
{
        struct switchdev_attr attr = {
                .orig_dev = p->br->dev,
                .id = SWITCHDEV_ATTR_ID_BRIDGE_VLAN_FILTERING,
                .flags = SWITCHDEV_F_SKIP_EOPNOTSUPP,
                .u.vlan_filtering = p->br->vlan_enabled,
        };
        struct net_bridge_vlan_group *vg;
        int ret = -ENOMEM;

        vg = kzalloc(sizeof(struct net_bridge_vlan_group), GFP_KERNEL);
        if (!vg)
                goto out;

        ret = switchdev_port_attr_set(p->dev, &attr);
        if (ret && ret != -EOPNOTSUPP)
                goto err_vlan_enabled;

        ret = rhashtable_init(&vg->vlan_hash, &br_vlan_rht_params);
        if (ret)
                goto err_rhtbl;
        ret = vlan_tunnel_init(vg);
        if (ret)
                goto err_tunnel_init;
        INIT_LIST_HEAD(&vg->vlan_list);
        rcu_assign_pointer(p->vlgrp, vg);
        if (p->br->default_pvid) {
                ret = nbp_vlan_add(p, p->br->default_pvid,
                                   BRIDGE_VLAN_INFO_PVID |
                                   BRIDGE_VLAN_INFO_UNTAGGED);

Now, i just noticed the switchdev call above. I don't think the DSA
layer implements SWITCHDEV_ATTR_ID_BRIDGE_VLAN_FILTERING. It probably
should. So what is it supposed to do with this VLAN when filtering is
disabled?

        Andrew