| Message ID | 20250424223734.3096202-1-vladimir.oltean@nxp.com |
|---|---|
| State | New |
| Headers | show |
| Series | [net,1/2] net: mscc: ocelot: delete PVID VLAN when readding it as non-PVID | expand |
On Fri, Apr 25, 2025 at 01:37:34AM +0300, Vladimir Oltean wrote: > Recent discussions around commit ad1afb003939 ("vlan_dev: VLAN 0 should > be treated as "no vlan tag" (802.1p packet)") have sparked the question > what happens with the DSA (and possibly other switchdev) data path when > the bridge says that ports should have no PVID VLAN, but the 8021q > module, as the result of a NETDEV_UP event, decides it should add VID 0 > to the RX filter of those bridge ports. Do those bridge ports receive > packets tagged with VID 0 or not, now? We don't know, there is no test. > > In the veth realm, this passes trivially, because veth is not VLAN > filtering and this, the 8021q module lacks the instinct to add VID 0 in > the first place. > > In the realm of VLAN filtering NICs with no switchdev offload, this > should also pass, because the VLAN groups of the software bridge are > consulted, where it can clearly be seen that a PVID is missing, even > though the packet was initially accepted by the NIC. > > The test only poses a challenge for switchdev drivers, which usually > have to program to hardware both VLANs from RX filtering, as well as > from switchdev. Especially when a switchdev port joins a VLAN-aware > bridge, it is unavoidable that it gains the NETIF_F_HW_VLAN_CTAG_FILTER > feature, i.e. any 8021q uppers that the bridge port may have must also > be committed to the RX filtering table of the interface. When a > VLAN-tagged packet is physically received by the port, it is initially > indistinguishable whether it will reach the bridge data path or the > 8021q upper data path. > > That is rather the final step of the new tests that we introduce. > We need to build context up to that stage, which means the following: > > - we need to test that 802.1p (VID 0) tagged traffic is received in the > first place (on bridge ports with a valid PVID). This is the "8021p" > test. > > - we need to test that the usual paths of reaching a configuration with > no PVID on a bridge port are all covered and they all reach the same > state. > > Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Reviewed-by: Ido Schimmel <idosch@nvidia.com> Tested-by: Ido Schimmel <idosch@nvidia.com>
diff --git a/drivers/net/ethernet/mscc/ocelot.c b/drivers/net/ethernet/mscc/ocelot.c index ef93df520887..08bee56aea35 100644 --- a/drivers/net/ethernet/mscc/ocelot.c +++ b/drivers/net/ethernet/mscc/ocelot.c @@ -830,6 +830,7 @@ EXPORT_SYMBOL(ocelot_vlan_prepare); int ocelot_vlan_add(struct ocelot *ocelot, int port, u16 vid, bool pvid, bool untagged) { + struct ocelot_port *ocelot_port = ocelot->ports[port]; int err; /* Ignore VID 0 added to our RX filter by the 8021q module, since @@ -849,6 +850,11 @@ int ocelot_vlan_add(struct ocelot *ocelot, int port, u16 vid, bool pvid, ocelot_bridge_vlan_find(ocelot, vid)); if (err) return err; + } else if (ocelot_port->pvid_vlan && + ocelot_bridge_vlan_find(ocelot, vid) == ocelot_port->pvid_vlan) { + err = ocelot_port_set_pvid(ocelot, port, NULL); + if (err) + return err; } /* Untagged egress vlan clasification */
The following set of commands: ip link add br0 type bridge vlan_filtering 1 # vlan_default_pvid 1 is implicit ip link set swp0 master br0 bridge vlan add dev swp0 vid 1 should result in the dropping of untagged and 802.1p-tagged traffic, but we see that it continues to be accepted. Whereas, had we deleted VID 1 instead, the aforementioned dropping would have worked This is because the ANA_PORT_DROP_CFG update logic doesn't run, because ocelot_vlan_add() only calls ocelot_port_set_pvid() if the new VLAN has the BRIDGE_VLAN_INFO_PVID flag. Similar to other drivers like mt7530_port_vlan_add() which handle this case correctly, we need to test whether the VLAN we're changing used to have the BRIDGE_VLAN_INFO_PVID flag, but lost it now. That amounts to a PVID deletion and should be treated as such. Regarding blame attribution: this never worked properly since the introduction of bridge VLAN filtering in commit 7142529f1688 ("net: mscc: ocelot: add VLAN filtering"). However, there was a significant paradigm shift which aligned the ANA_PORT_DROP_CFG register with the PVID concept rather than with the native VLAN concept, and that change wasn't targeted for 'stable'. Realistically, that is as far as this fix needs to be propagated to. Fixes: be0576fed6d3 ("net: mscc: ocelot: move the logic to drop 802.1p traffic to the pvid deletion") Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> --- drivers/net/ethernet/mscc/ocelot.c | 6 ++++++ 1 file changed, 6 insertions(+)