On 3/23/2019 8:23 PM, Vladimir Oltean wrote:

In order to support this, we are creating a make-shift switch tag out of
a VLAN trunk configured on the CPU port. Termination on switch ports
only works when not under a vlan_filtering bridge. We are making use of
the generic CONFIG_NET_DSA_TAG_8021Q code and leveraging it from our own
CONFIG_NET_DSA_TAG_SJA1105.

There are two types of traffic: regular and link-local.
The link-local traffic received on the CPU port is trapped from the
switch's regular forwarding decisions because it matched one of the two
DMAC filters for management traffic.
On transmission, the switch requires special massaging for these
link-local frames. Due to a weird implementation of the switching IP, by
default it drops link-local frames that originate on the CPU port. It
needs to be told where to forward them to, through an SPI command
("management route") that is valid for only a single frame.
So when we're sending link-local traffic, we need to clone skb's from
DSA and send them in our custom xmit worker that also performs SPI access.

For that purpose, the DSA xmit handler and the xmit worker communicate
through a per-port "skb ring" software structure, with a producer and a
consumer index. At the moment this structure is rather fragile
(ping-flooding to a link-local DMAC would cause most of the frames to
get dropped). I would like to move the management traffic on a separate
netdev queue that I can stop when the skb ring got full and hardware is
busy processing, so that we are not forced to drop traffic.

Signed-off-by: Vladimir Oltean <olteanv@gmail.com>

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

I do like the idea of setting up specific management queue later on,
although it is not clear to me how you would go about integrating it as
a network device, given the DSA slave and master devices, do you know
roughly how you would proceed?
-- 
Florian