netdev - Re: [PATCH net 2/2] net: mscc: ocelot: refuse to overwrite the port's native vlan

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Message-ID: <5a0b7e8b-851e-2523-c6c1-da6fbd0c3dac@gmail.com>
Date:   Sat, 26 Oct 2019 13:33:55 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>, davem@...emloft.net
Cc:     netdev@...r.kernel.org, joergen.andreasen@...rochip.com,
        allan.nielsen@...rochip.com, antoine.tenart@...tlin.com,
        alexandre.belloni@...tlin.com, vivien.didelot@...il.com,
        andrew@...n.ch
Subject: Re: [PATCH net 2/2] net: mscc: ocelot: refuse to overwrite the port's
 native vlan



On 10/26/2019 11:04 AM, Vladimir Oltean wrote:
> The switch driver keeps a "vid" variable per port, which signifies _the_
> VLAN ID that is stripped on that port's egress (aka the native VLAN on a
> trunk port).
> 
> That is the way the hardware is designed (mostly). The port->vid is
> programmed into REW:PORT:PORT_VLAN_CFG:PORT_VID and the rewriter is told
> to send all traffic as tagged except the one having port->vid.
> 
> There exists a possibility of finer-grained egress untagging decisions:
> using the VCAP IS1 engine, one rule can be added to match every
> VLAN-tagged frame whose VLAN should be untagged, and set POP_CNT=1 as
> action. However, the IS1 can hold at most 512 entries, and the VLANs are
> in the order of 6 * 4096.
> 
> So the code is fine for now. But this sequence of commands:
> 
> $ bridge vlan add dev swp0 vid 1 pvid untagged
> $ bridge vlan add dev swp0 vid 2 untagged
> 
> makes untagged and pvid-tagged traffic be sent out of swp0 as tagged
> with VID 1, despite user's request.
> 
> Prevent that from happening. The user should temporarily remove the
> existing untagged VLAN (1 in this case), add it back as tagged, and then
> add the new untagged VLAN (2 in this case).>
> Cc: Antoine Tenart <antoine.tenart@...tlin.com>
> Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>
> Fixes: 7142529f1688 ("net: mscc: ocelot: add VLAN filtering")
> Signed-off-by: Vladimir Oltean <olteanv@...il.com>

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

[snip]

> +	if (untagged && port->vid != vid) {
> +		if (port->vid) {
> +			dev_err(ocelot->dev,
> +				"Port already has a native VLAN: %d\n",
> +				port->vid);

This sounds like a extended netlink ack candidate for improving user
experience, but this should do for now.
-- 
Florian