Re: [RFC PATCH] net: dsa: microchip: Prevent overriding of HSR port forwarding

["Łukasz Majewski" <lukma@nabladev.com>]

On Wed, 13 Aug 2025 17:57:02 +0200
Frieder Schrempf <frieder.schrempf@kontron.de> wrote:

> Am 13.08.25 um 17:45 schrieb Łukasz Majewski:
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> > 
> > Hi Frieder,
> >   
> >> From: Frieder Schrempf <frieder.schrempf@kontron.de>
> >>
> >> The KSZ9477 supports NETIF_F_HW_HSR_FWD to forward packets between
> >> HSR ports. This is set up when creating the HSR interface via
> >> ksz9477_hsr_join() and ksz9477_cfg_port_member().
> >>
> >> At the same time ksz_update_port_member() is called on every
> >> state change of a port and reconfiguring the forwarding to the
> >> default state which means packets get only forwarded to the CPU
> >> port.
> >>
> >> If the ports are brought up before setting up the HSR interface
> >> and then the port state is not changed afterwards, everything works
> >> as intended:
> >>
> >>   ip link set lan1 up
> >>   ip link set lan2 up
> >>   ip link add name hsr type hsr slave1 lan1 slave2 lan2 supervision
> >> 45 version 1 ip addr add dev hsr 10.0.0.10/24
> >>   ip link set hsr up
> >>
> >> If the port state is changed after creating the HSR interface, this
> >> results in a non-working HSR setup:
> >>
> >>   ip link add name hsr type hsr slave1 lan1 slave2 lan2 supervision
> >> 45 version 1 ip addr add dev hsr 10.0.0.10/24
> >>   ip link set lan1 up
> >>   ip link set lan2 up
> >>   ip link set hsr up
> >>
> >> In this state, packets will not get forwarded between the HSR ports
> >> and communication between HSR nodes that are not direct neighbours
> >> in the topology fails.
> >>
> >> To avoid this, we prevent all forwarding reconfiguration requests
> >> for ports that are part of a HSR setup with NETIF_F_HW_HSR_FWD
> >> enabled.
> >>
> >> Fixes: 2d61298fdd7b ("net: dsa: microchip: Enable HSR offloading
> >> for KSZ9477") Signed-off-by: Frieder Schrempf
> >> <frieder.schrempf@kontron.de> ---
> >> I'm posting this as RFC as my knowledge of the driver and the
> >> stack in general is very limited. Please review thoroughly and
> >> provide feedback. Thanks!  
> > 
> > I don't have the HW at hand at the moment (temporary).
> > 
> > Could you check if this patch works when you create two hsr
> > interfaces
> > - i.e. hsr1 would use HW offloading from KSZ9744 and hsr2 is just
> > the one supporting HSR in software.  
> 
> My hardware only has three user ports. So that might get a bit
> difficult to test. I will try to configure one unconnected port to
> set up two HSR links, but I won't be able to fully test this due to
> the lack of the fourth physical link.
> 

Ok, I see...

I was using the Atmel's/Microchip Devel board with 5 ports...

-- 
Best regards,

Lukasz Majewski

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