Re: [PATCH net-next 1/2] dsa: tag_mxl862xx: set dsa_default_offload_fwd_mark()

[Jonas Gorski]

On Sun, Mar 8, 2026 at 4:19 PM Daniel Golle <daniel@xxxxxxxxxxxxxx> wrote:
>
> On Sat, Mar 07, 2026 at 10:57:56AM +0100, Jonas Gorski wrote:
> > Hi,
> >
> > On 07/03/2026 04:30, Daniel Golle wrote:
> > > The MxL862xx offloads forwarding between bridged ports to the
> > > hardware, so set dsa_default_offload_fwd_mark() to avoid duplicate
> > > forwarding of packets of (eg. flooded) frames arriving at the CPU
> > > port.
> > >
> > > Signed-off-by: Daniel Golle <daniel@xxxxxxxxxxxxxx>
> > > ---
> > >  net/dsa/tag_mxl862xx.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/net/dsa/tag_mxl862xx.c b/net/dsa/tag_mxl862xx.c
> > > index 01f2158682718..c02f69de61cbb 100644
> > > --- a/net/dsa/tag_mxl862xx.c
> > > +++ b/net/dsa/tag_mxl862xx.c
> > > @@ -92,6 +92,8 @@ static struct sk_buff *mxl862_tag_rcv(struct sk_buff *skb,
> > >     skb_pull_rcsum(skb, MXL862_HEADER_LEN);
> > >     dsa_strip_etype_header(skb, MXL862_HEADER_LEN);
> > >
> > > +   dsa_default_offload_fwd_mark(skb);
> >
> > Does the switch (by default) also flood link local traffic (e.g. STP, LACP,
> > etc)? If not, you should not mark these as fwd offloaded.
>
> No, it doesn't. Testing revealed that apparently it silently consumes them.
> I assume we'll need something like
>
> if (likely(!is_link_local_ether_addr(eth_hdr(skb)->h_dest)))
>     dsa_default_offload_fwd_mark(skb);
>
> similar to tag_brcm.c, right?

Yepp, that would have been my suggestion :-)

> > Is there is a bit in the header that says whether a packet was flooded or
> > trapped that you can check?
>
> Earlier testing showed that frames arriving at the microcontroller under
> some conditions are relayed to the DSA CPU port -- and are destinguishable
> as such. However, there is not bit directly indicating whether the packet
> was (also) flooded already.

So you know if they were copied to the cpu port due to some rules, but
not if they were snooped or trapped?

Best regards,
Jonas