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From: Vladimir Oltean <olteanv@gmail.com>
To: DENG Qingfang <dqfext@gmail.com>
Cc: "Sean Wang" <sean.wang@mediatek.com>,
	"Landen Chao" <Landen.Chao@mediatek.com>,
	"Andrew Lunn" <andrew@lunn.ch>,
	"Vivien Didelot" <vivien.didelot@gmail.com>,
	"Florian Fainelli" <f.fainelli@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Matthias Brugger" <matthias.bgg@gmail.com>,
	netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
	"Eric Woudstra" <ericwouds@gmail.com>,
	"René van Dorst" <opensource@vdorst.com>,
	"Frank Wunderlich" <frank-w@public-files.de>
Subject: Re: [RFC net-next v2 1/4] net: dsa: mt7530: enable assisted learning on CPU port
Date: Mon, 2 Aug 2021 16:07:23 +0300	[thread overview]
Message-ID: <20210802130723.6tieexl5zcxu44xr@skbuf> (raw)
In-Reply-To: <20210731191023.1329446-2-dqfext@gmail.com>

On Sun, Aug 01, 2021 at 03:10:19AM +0800, DENG Qingfang wrote:
> Consider the following bridge configuration, where bond0 is not
> offloaded:
> 
>          +-- br0 --+
>         / /   |     \
>        / /    |      \
>       /  |    |     bond0
>      /   |    |     /   \
>    swp0 swp1 swp2 swp3 swp4
>      .        .       .
>      .        .       .
>      A        B       C
> 
> Address learning is enabled on offloaded ports (swp0~2) and the CPU
> port, so when client A sends a packet to C, the following will happen:
> 
> 1. The switch learns that client A can be reached at swp0.
> 2. The switch probably already knows that client C can be reached at the
>    CPU port, so it forwards the packet to the CPU.
> 3. The bridge core knows client C can be reached at bond0, so it
>    forwards the packet back to the switch.
> 4. The switch learns that client A can be reached at the CPU port.
> 5. The switch forwards the packet to either swp3 or swp4, according to
>    the packet's tag.
> 
> That makes client A's MAC address flap between swp0 and the CPU port. If
> client B sends a packet to A, it is possible that the packet is
> forwarded to the CPU. With offload_fwd_mark = 1, the bridge core won't
> forward it back to the switch, resulting in packet loss.
> 
> As we have the assisted_learning_on_cpu_port in DSA core now, enable
> that and disable hardware learning on the CPU port.
> 
> Signed-off-by: DENG Qingfang <dqfext@gmail.com>
> ---

Reviewed-by: Vladimir Oltean <oltean@gmail.com>

  reply	other threads:[~2021-08-02 13:07 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-31 19:10 [RFC net-next v2 0/4] mt7530 software fallback bridging fix DENG Qingfang
2021-07-31 19:10 ` [RFC net-next v2 1/4] net: dsa: mt7530: enable assisted learning on CPU port DENG Qingfang
2021-08-02 13:07   ` Vladimir Oltean [this message]
2021-07-31 19:10 ` [RFC net-next v2 2/4] net: dsa: mt7530: use independent VLAN learning on VLAN-unaware bridges DENG Qingfang
2021-08-02 13:36   ` Vladimir Oltean
2021-07-31 19:10 ` [RFC net-next v2 3/4] net: dsa: mt7530: set STP state also on filter ID 1 DENG Qingfang
2021-08-02 13:43   ` Vladimir Oltean
2021-08-02 15:31     ` DENG Qingfang
2021-08-02 15:42       ` Vladimir Oltean
2021-08-02 15:58         ` DENG Qingfang
2021-08-02 21:00           ` Vladimir Oltean
2021-08-03  8:23             ` DENG Qingfang
2021-08-03  8:48               ` Vladimir Oltean
2021-07-31 19:10 ` [RFC net-next v2 4/4] Revert "mt7530 mt7530_fdb_write only set ivl bit vid larger than 1" DENG Qingfang
2021-08-02 13:44   ` Vladimir Oltean
2021-08-02 15:48     ` DENG Qingfang
2021-08-02 20:59       ` Vladimir Oltean

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