Re: [RFC net-next 2/3] net: dsa: qca8k: enable assisted learning on CPU port

From: Vladimir Oltean <olteanv@gmail.com>
To: Andre Valentin <avalentin@marcant.net>
Cc: "DENG Qingfang" <dqfext@gmail.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>,
	"Russell King" <linux@armlinux.org.uk>,
	"open list:NETWORKING DRIVERS" <netdev@vger.kernel.org>,
	"open list" <linux-kernel@vger.kernel.org>,
	"Ansuel Smith" <ansuelsmth@gmail.com>,
	"Jonathan McDowell" <noodles@earth.li>,
	"Michal Vokáč" <vokac.m@gmail.com>,
	"Christian Lamparter" <chunkeey@gmail.com>,
	"Nishka Dasgupta" <nishkadg.linux@gmail.com>,
	"John Crispin" <john@phrozen.org>,
	"Stefan Lippers-Hollmann" <s.l-h@gmx.de>,
	"Hannu Nyman" <hannu.nyman@iki.fi>,
	"Imran Khan" <gururug@gmail.com>,
	"Frank Wunderlich" <frank-w@public-files.de>,
	"Nick Lowe" <nick.lowe@gmail.com>
Subject: Re: [RFC net-next 2/3] net: dsa: qca8k: enable assisted learning on CPU port
Date: Tue, 10 Aug 2021 20:53:24 +0300	[thread overview]
Message-ID: <20210810175324.ijodmycvxfnwu4yf@skbuf> (raw)
In-Reply-To: <0072b721-7520-365d-26ef-a2ad70117ac2@marcant.net>

On Tue, Aug 10, 2021 at 07:27:05PM +0200, Andre Valentin wrote:
> On Sun, Aug 08, 2021 at 1805, DENG Qingfang wrote:
> > On Sun, Aug 08, 2021 at 01:25:55AM +0300, Vladimir Oltean wrote:
> >> On Sat, Aug 07, 2021 at 08:07:25PM +0800, DENG Qingfang wrote:
> >>> Enable assisted learning on CPU port to fix roaming issues.
> >>
> >> 'roaming issues' implies to me it suffered from blindness to MAC
> >> addresses learned on foreign interfaces, which appears to not be true
> >> since your previous patch removes hardware learning on the CPU port
> >> (=> hardware learning on the CPU port was supported, so there were no
> >> roaming issues)
>
> The issue is with a wifi AP bridged into dsa and previously learned
> addresses.
>
> Test setup:
> We have to wifi APs a and b(with qca8k). Client is on AP a.
>
> The qca8k switch in AP b sees also the broadcast traffic from the client
> and takes the address into its fdb.
>
> Now the client roams to AP b.
> The client starts DHCP but does not get an IP. With tcpdump, I see the
> packets going through the switch (ap->cpu port->ethernet port) and they
> arrive at the DHCP server. It responds, the response packet reaches the
> ethernet port of the qca8k, and is not forwarded.
>
> After about 3 minutes the fdb entry in the qca8k on AP b is
> "cleaned up" and the client can immediately get its IP from the DHCP server.
>
> I hope this helps understanding the background.

How does this differ from what is described in commit d5f19486cee7
("net: dsa: listen for SWITCHDEV_{FDB,DEL}_ADD_TO_DEVICE on foreign
bridge neighbors")?