RE: [EXT] Re: [PATCH v4 2/2] net: dsa: ocelot: Add support for QinQ Operation

[Hongbo Wang <hongbo.wang@nxp.com>]

> On 8/3/2020 11:36 PM, Hongbo Wang wrote:
> >>> +     if (vlan->proto == ETH_P_8021AD) {
> >>> +             ocelot->enable_qinq = true;
> >>> +             ocelot_port->qinq_mode = true;
> >>> +     }
> >>  ...
> >>> +     if (vlan->proto == ETH_P_8021AD) {
> >>> +             ocelot->enable_qinq = false;
> >>> +             ocelot_port->qinq_mode = false;
> >>> +     }
> >>> +
> >>
> >> I don't understand how this can work just by using a boolean to track
> >> the state.
> >>
> >> This won't work properly if you are handling multiple QinQ VLAN entries.
> >>
> >> Also, I need Andrew and Florian to review and ACK the DSA layer
> >> changes that add the protocol value to the device notifier block.
> >
> > Hi David,
> > Thanks for reply.
> >
> > When setting bridge's VLAN protocol to 802.1AD by the command "ip link
> > set br0 type bridge vlan_protocol 802.1ad", it will call
> > dsa_slave_vlan_rx_add(dev, proto, vid) for every port in the bridge,
> > the parameter vid is port's pvid 1, if pvid's proto is 802.1AD, I will
> > enable switch's enable_qinq, and the related port's qinq_mode,
> >
> > When there are multiple QinQ VLAN entries, If one VLAN's proto is 802.1AD,
> I will enable switch and the related port into QinQ mode.
> 
> The enabling appears fine, the problem is the disabling, the first 802.1AD VLAN
> entry that gets deleted will lead to the port and switch no longer being in QinQ
> mode, and this does not look intended.
> --
> Florian

When I try to add reference counter, I found that:
1.
the command "ip link set br0 type bridge vlan_protocol 802.1ad" call path is:
br_changelink -> __br_vlan_set_proto -> vlan_vid_add -> ... -> ndo_vlan_rx_add_vid -> dsa_slave_vlan_rx_add_vid(dev, proto, vid) -> felix_vlan_add

dsa_slave_vlan_rx_add_vid can pass correct protocol and vid(1) to ocelot driver.

vlan_vid_add is in net/8021q/vlan_core.c, it maintains a vid_list that stores the map of vid and protocol,
the function vlan_vid_info_get can read the map.

but when deleting bridge using "ip link del dev br0 type bridge", the call path is:
br_dev_delete -> ... -> br_switchdev_port_vlan_del -> ... -> dsa_slave_port_obj_del -> dsa_slave_vlan_del -> ... -> felix_vlan_del

br_switchdev_port_vlan_del is in net/bridge/br_switchdev.c, it didn't have the list for map vid and protocol,
so it can't pass correct protocol that corresponding with vid to ocelot driver.

2.
For ocelot QinQ case, the switch port linked to customer has different actions with the port for ISP,

uplink: Customer LAN(CTAG) -> swp0(vlan_aware:0 pop_cnt:0) -> swp1(add STAG) -> ISP MAN(STAG + CTAG)
downlink: ISP MAN(STAG + CTAG) -> swp1(vlan_aware:1 pop_cnt:1, pop STAG) -> swp0(only CTAG) -> Customer LAN

the different action is descripted in "4.3.3 Provider Bridges and Q-in-Q Operation" in VSC99599_1_00_TS.pdf

so I need a standard command to set swp0 and swp1 for different mode, 
but "ip link set br0 type bridge vlan_protocol 802.1ad" will set all ports into the same mode, it's not my intent.

3.
I thought some ways to resovle the above issue:
a. br_switchdev_port_vlan_del will pass default value ETH_P_8021Q, but don't care it in felix_vlan_del.
b. In felix_vlan_add and felix_vlan_del, only when vid is ocelot_port's pvid, it enable or disable switch's enable_qinq.
c. Maybe I can use devlink to set swp0 and swp1 into different mode.
d. let br_switchdev_port_vlan_del call vlan_vid_info_get to get protocol for vid, but vlan_vid_info_get is static in vlan_core.c, so this need to add related functions in br_switchdev.c.

Any comments is welcome!

Thanks
Hongbo