netdev - Re: [RFC v2, net-next, PATCH 0/4] Add switchdev on TI-CPSW

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Message-ID: <20180618173025.GF5865@lunn.ch>
Date:   Mon, 18 Jun 2018 19:30:25 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Ilias Apalodimas <ilias.apalodimas@...aro.org>
Cc:     netdev@...r.kernel.org, grygorii.strashko@...com,
        ivan.khoronzhuk@...aro.org, nsekhar@...com, jiri@...nulli.us,
        ivecera@...hat.com, f.fainelli@...il.com, francois.ozog@...aro.org,
        yogeshs@...com, spatton@...com, Jose.Abreu@...opsys.com
Subject: Re: [RFC v2, net-next, PATCH 0/4] Add switchdev on TI-CPSW

On Mon, Jun 18, 2018 at 07:46:02PM +0300, Ilias Apalodimas wrote:
> On Mon, Jun 18, 2018 at 06:28:36PM +0200, Andrew Lunn wrote:
> > > Yes, if the CPU port is added on the VLAN then unregistered multicast traffic
> > > (and thus IGMP joins) will reach the CPU port and everything will work as
> > > expected. I think we should not consider this as a "problem" as long as it's
> > > descibed properly in Documentation. This switch is excected to support this.
> > 
> > Back to the two e1000e. What would you expect to happen with them?
> > Either IGMP snooping needs to work, or your don't do snooping at
> > all.
> That's a different use case

I disagree. That is the exact same use case. I add ports to a bridge
and i expect the bridge to either do IGMP snooping, or just forward
all multicast. That is the users expectations. That is how the Linux
network stack works. If the hardware has limitations you want to try
to hide them from the user.

> > So by default, it just needs to work. You can give the user the option
> > to shoot themselves in the foot, but they need to actively pull the
> > trigger to blow their own foot off.

> Yes it does by default. I don't consider it "foot shooting" though. 
> If we stop thinking about switches connected to user environments 

I never think about switches. I think about a block of acceleration
hardware, which i try to offload Linux networking to. And if the
hardware cannot accelerate Linux network functions properly, i don't
try to offload it. That way it always operates in the same way, and
the user expectations are clear.

    Andrew