Re: [PATCH v5 net-next 10/10] net: dsa: felix: perform switch setup for tag_8021q

[Florian Fainelli <f.fainelli@gmail.com>]

On 1/20/2021 6:36 PM, Vladimir Oltean wrote:
> From: Vladimir Oltean <vladimir.oltean@nxp.com>
> 
> Unlike sja1105, the only other user of the software-defined tag_8021q.c
> tagger format, the implementation we choose for the Felix DSA switch
> driver preserves full functionality under a vlan_filtering bridge
> (i.e. IP termination works through the DSA user ports under all
> circumstances).
> 
> The tag_8021q protocol just wants:
> - Identifying the ingress switch port based on the RX VLAN ID, as seen
>   by the CPU. We achieve this by using the TCAM engines (which are also
>   used for tc-flower offload) to push the RX VLAN as a second, outer
>   tag, on egress towards the CPU port.
> - Steering traffic injected into the switch from the network stack
>   towards the correct front port based on the TX VLAN, and consuming
>   (popping) that header on the switch's egress.
> 
> A tc-flower pseudocode of the static configuration done by the driver
> would look like this:
> 
> $ tc qdisc add dev <cpu-port> clsact
> $ for eth in swp0 swp1 swp2 swp3; do \
> 	tc filter add dev <cpu-port> egress flower indev ${eth} \
> 		action vlan push id <rxvlan> protocol 802.1ad; \
> 	tc filter add dev <cpu-port> ingress protocol 802.1Q flower
> 		vlan_id <txvlan> action vlan pop \
> 		action mirred egress redirect dev ${eth}; \
> done
> 
> but of course since DSA does not register network interfaces for the CPU
> port, this configuration would be impossible for the user to do. Also,
> due to the same reason, it is impossible for the user to inadvertently
> delete these rules using tc. These rules do not collide in any way with
> tc-flower, they just consume some TCAM space, which is something we can
> live with.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>

Quite an interesting read.
-- 
Florian