linux-kernel - Re: [PATCH v8 net-next 05/12] net: dsa: propagate the locked flag down through the DSA layer

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Message-ID: <20221020133506.76wroc7owpwjzrkg@skbuf>
Date:   Thu, 20 Oct 2022 16:35:06 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Ido Schimmel <idosch@...dia.com>
Cc:     "Hans J. Schultz" <netdev@...io-technology.com>,
        davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Woojung Huh <woojung.huh@...rochip.com>,
        UNGLinuxDriver@...rochip.com, Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Ivan Vecera <ivecera@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Shuah Khan <shuah@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Christian Marangi <ansuelsmth@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Yuwei Wang <wangyuweihx@...il.com>,
        Petr Machata <petrm@...dia.com>,
        Florent Fourcot <florent.fourcot@...irst.fr>,
        Hans Schultz <schultz.hans@...il.com>,
        Joachim Wiberg <troglobit@...il.com>,
        Amit Cohen <amcohen@...dia.com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        bridge@...ts.linux-foundation.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v8 net-next 05/12] net: dsa: propagate the locked flag
 down through the DSA layer

On Thu, Oct 20, 2022 at 04:24:16PM +0300, Ido Schimmel wrote:
> On Thu, Oct 20, 2022 at 04:02:24PM +0300, Vladimir Oltean wrote:
> > On Tue, Oct 18, 2022 at 06:56:12PM +0200, Hans J. Schultz wrote:
> > > @@ -3315,6 +3316,7 @@ static int dsa_slave_fdb_event(struct net_device *dev,
> > >  	struct dsa_port *dp = dsa_slave_to_port(dev);
> > >  	bool host_addr = fdb_info->is_local;
> > >  	struct dsa_switch *ds = dp->ds;
> > > +	u16 fdb_flags = 0;
> > >  
> > >  	if (ctx && ctx != dp)
> > >  		return 0;
> > > @@ -3361,6 +3363,9 @@ static int dsa_slave_fdb_event(struct net_device *dev,
> > >  		   orig_dev->name, fdb_info->addr, fdb_info->vid,
> > >  		   host_addr ? " as host address" : "");
> > >  
> > > +	if (fdb_info->locked)
> > > +		fdb_flags |= DSA_FDB_FLAG_LOCKED;
> > 
> > This is the bridge->driver direction. In which of the changes up until
> > now/through which mechanism will the bridge emit a
> > SWITCHDEV_FDB_ADD_TO_DEVICE with fdb_info->locked = true?
> 
> I believe it can happen in the following call chain:
> 
> br_handle_frame_finish
>    br_fdb_update // p->flags & BR_PORT_MAB
>        fdb_notify
>            br_switchdev_fdb_notify
> 
> This can happen with Spectrum when a packet ingresses via a locked port
> and incurs an FDB miss in hardware. The packet will be trapped and
> injected to the Rx path where it should invoke the above call chain.

Ah, so this is the case which in mv88e6xxx would generate an ATU
violation interrupt; in the Spectrum case it generates a special packet.
Right now this packet isn't generated, right?

I think we have the same thing in ocelot, a port can be configured to
send "learn frames" to the CPU.

Should these packets be injected into the bridge RX path in the first
place? They reach the CPU because of an FDB miss, not because the CPU
was the intended destination.