netdev - Re: [PATCH net-next] net: dsa: hellcreek: Offload bridge port flags

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Message-ID: <20210315213413.k4td2urqxl2sqflg@skbuf>
Date:   Mon, 15 Mar 2021 23:34:13 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Kurt Kanzenbach <kurt@...-computers.de>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net: dsa: hellcreek: Offload bridge port flags

On Mon, Mar 15, 2021 at 09:33:44PM +0100, Kurt Kanzenbach wrote:
> On Mon Mar 15 2021, Vladimir Oltean wrote:
> > On Sun, Mar 14, 2021 at 01:52:08PM +0100, Kurt Kanzenbach wrote:
> >> +	if (enable)
> >> +		val &= ~HR_PTCFG_UUC_FLT;
> >> +	else
> >> +		val |= HR_PTCFG_UUC_FLT;
> >
> > What does 'unknown unicast filtering' mean/do, exactly?
> > The semantics of BR_FLOOD are on egress: all unicast packets with an
> > unknown destination that are received on ports from this bridging domain
> > can be flooded towards port X if that port has flooding enabled.
> > When I hear "filtering", I imagine an ingress setting, am I wrong?
> 
> It means that frames without matching fdb entries towards this port are
> discarded.

The phrasing is still not crystal clear, sorry.
You have a switch with 2 user ports, lan0 and lan1, and one CPU port.
lan0 and lan1 are under br0. lan0 has 'unknown unicast filtering'
disabled, lan1 has it enabled, and the CPU port has it disabled.
You receive a packet from lan0 towards an unknown unicast destination.
Is the packet discarded or is it sent to the CPU port?