Hello, On 31/10/2020 12:29:10+0200, Vladimir Oltean wrote: > Currently, mscc_ocelot ports configure pvid=0 in standalone mode, and > inherit the pvid from the bridge when one is present. > > When the bridge has vlan_filtering=0, the software semantics are that > packets should be received regardless of whether there's a pvid > configured on the ingress port or not. However, ocelot does not observe > those semantics today. > > Moreover, changing the PVID is also a problem with vlan_filtering=0. > We are privately remapping the VID of FDB, MDB entries to the port's > PVID when those are VLAN-unaware (i.e. when the VID of these entries > comes to us as 0). But we have no logic of adjusting that remapping when > the user changes the pvid and vlan_filtering is 0. So stale entries > would be left behind, and untagged traffic will stop matching on them. > > And even if we were to solve that, there's an even bigger problem. If > swp0 has pvid 1, and swp1 has pvid 2, and both are under a vlan_filtering=0 > bridge, they should be able to forward traffic between one another. > However, with ocelot they wouldn't do that. > > The simplest way of fixing this is to never configure the pvid based on > what the bridge is asking for, when vlan_filtering is 0. Only if there > was a VLAN that the bridge couldn't mangle, that we could use as pvid.... > So, turns out, there's 0 just for that. And for a reason: IEEE > 802.1Q-2018, page 247, Table 9-2-Reserved VID values says: > > The null VID. Indicates that the tag header contains only > priority information; no VID is present in the frame. > This VID value shall not be configured as a PVID or a member > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > of a VID Set, or configured in any FDB entry, or used in any > Management operation. > > So, aren't we doing exactly what 802.1Q says not to? Well, in a way, but > what we're doing here is just driver-level bookkeeping, all for the > better. The fact that we're using a pvid of 0 is not observable behavior > from the outside world: the network stack does not see the classified > VLAN that the switch uses, in vlan_filtering=0 mode. And we're also more > consistent with the standalone mode now. >
IIRC, we are using pvid 1 because else bridging breaks when CONFIG_VLAN_8021Q is not enabled. Did you test that configuration? -- Alexandre Belloni, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
