netdev - Re: [PATCH net] net: dsa: flood multicast to CPU when slave has IFF

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Date:   Thu, 21 Apr 2022 16:20:59 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Vladimir Oltean <vladimir.oltean@....com>, netdev@...r.kernel.org
Cc:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>
Subject: Re: [PATCH net] net: dsa: flood multicast to CPU when slave has
 IFF_PROMISC

On 4/21/22 15:42, Vladimir Oltean wrote:
> Certain DSA switches can eliminate flooding to the CPU when none of the
> ports have the IFF_ALLMULTI or IFF_PROMISC flags set. This is done by
> synthesizing a call to dsa_port_bridge_flags() for the CPU port, a call
> which normally comes from the bridge driver via switchdev.
> 
> The bridge port flags and IFF_PROMISC|IFF_ALLMULTI have slightly
> different semantics, and due to inattention/lack of proper testing, the
> IFF_PROMISC flag allows unknown unicast to be flooded to the CPU, but
> not unknown multicast.
> 
> This must be fixed by setting both BR_FLOOD (unicast) and BR_MCAST_FLOOD
> in the synthesized dsa_port_bridge_flags() call, since IFF_PROMISC means
> that packets should not be filtered regardless of their MAC DA.
> 
> Fixes: 7569459a52c9 ("net: dsa: manage flooding on the CPU ports")
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>

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