netdev - Re: [PATCH net-next] net: dsa: mv88e6xxx: Add support for port mirroring

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Message-ID: <20190917223232.GA32887@i5wan>
Date:   Wed, 18 Sep 2019 00:32:32 +0200
From:   Iwan R Timmer <irtimmer@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net: dsa: mv88e6xxx: Add support for port
 mirroring

On Tue, Sep 17, 2019 at 10:55:05PM +0200, Andrew Lunn wrote:
> On Tue, Sep 17, 2019 at 10:23:01PM +0200, Iwan R Timmer wrote:
> > Add support for configuring port mirroring through the cls_matchall
> > classifier. We do a full ingress and/or egress capture towards the
> > capture port, configured with set_egress_port.
> 
> Hi Iwan
> 
> This looks good as far as it goes.
> 
> Have you tried adding/deleting multiple port mirrors? Do we need to
> limit how many are added. A quick look at the datasheet, you can
> define one egress mirror port and one ingress mirror port. I think you
> can have multiple ports mirroring ingress to that one ingress mirror
> port. And you can have multiple port mirroring egress to the one
> egress mirror port. We should add code to check this, and return
> -EBUSY if the existing configuration prevents a new mirror being
> configured.
> 
> Thanks
> 	Andrew

Hi Andrew,

I only own a simple 5 ports switch (88E6176) which has no problem of
mirroring the other ports to a single port. Except for a bandwith
shortage ofcourse. While I thought I checked adding and removing ports,
I seemed to forgot to check removing ingress traffic as it will now
disable mirroring egress traffic. Searching for how I can distinct
ingress from egress mirroring in port_mirror_del, I saw there is a
variable in the mirror struct called ingress. Which seems strange,
because why is it a seperate argument to the port_mirror_add function?

Origally I planned to be able to set the egress and ingress mirror
seperatly. But in my laziness when I saw there already was a function
to configure the destination port this functionality was lost.

Because the other drivers which implemented the port_mirror_add (b53 and
ksz9477) also lacks additional checks to prevent new mirror filters from
breaking previous ones I assumed they were not necessary.

At least I will soon sent a new version with at least the issue of
removing mirror ingress traffic fixed and the ability to define a 
seperate ingress and egress port.

Regards,
Iwan