On 1/20/2021 6:36 PM, Vladimir Oltean wrote:
> From: Vladimir Oltean <vladimir.olt...@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.olt...@nxp.com>
Reviewed-by: Florian Fainelli <f.faine...@gmail.com>
Quite an interesting read.
--
Florian
