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

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Message-ID: <d7b430cf-7b28-49af-91f9-6b0da0f81c6a@lunn.ch>
Date: Fri, 15 Aug 2025 00:59:31 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Frieder Schrempf <frieder@...s.de>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, linux-kernel@...r.kernel.org,
	Lukasz Majewski <lukma@...x.de>, Paolo Abeni <pabeni@...hat.com>,
	UNGLinuxDriver@...rochip.com, Vladimir Oltean <olteanv@...il.com>,
	Woojung Huh <woojung.huh@...rochip.com>,
	Frieder Schrempf <frieder.schrempf@...tron.de>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Jesse Van Gavere <jesseevg@...il.com>,
	Oleksij Rempel <o.rempel@...gutronix.de>,
	Pieter Van Trappen <pieter.van.trappen@...n.ch>,
	"Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
	Simon Horman <horms@...nel.org>,
	Tristram Ha <tristram.ha@...rochip.com>,
	Vadim Fedorenko <vadim.fedorenko@...ux.dev>
Subject: Re: [RFC PATCH] net: dsa: microchip: Prevent overriding of HSR port
 forwarding

On Wed, Aug 13, 2025 at 05:26:12PM +0200, Frieder Schrempf wrote:
> From: Frieder Schrempf <frieder.schrempf@...tron.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

So, restating what i said in a different thread, what happens if only
software was used? No hardware offload.

	Andrew