netdev - Re: [PATCH net-next 2/9] net: bridge: offload initial and final port flags through switchdev

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Message-ID: <20210208114511.xtzma5byrdnr5s7r@skbuf>
Date:   Mon, 8 Feb 2021 13:45:11 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Nikolay Aleksandrov <nikolay@...dia.com>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        bridge@...ts.linux-foundation.org, Roopa Prabhu <roopa@...dia.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Ido Schimmel <idosch@...sch.org>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com, Vadym Kochan <vkochan@...vell.com>,
        Taras Chornyi <tchornyi@...vell.com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Ivan Vecera <ivecera@...hat.com>, linux-omap@...r.kernel.org
Subject: Re: [PATCH net-next 2/9] net: bridge: offload initial and final port
 flags through switchdev

On Mon, Feb 08, 2021 at 01:37:03PM +0200, Nikolay Aleksandrov wrote:
> Hi Vladimir,
> I think this patch potentially breaks some use cases. There are a few problems, I'll
> start with the more serious one: before the ports would have a set of flags that were
> always set when joining, now due to how nbp_flags_change() handles flag setting some might
> not be set which would immediately change behaviour w.r.t software fwding. I'll use your
> example of BR_BCAST_FLOOD: a lot of drivers will return an error for it and any broadcast
> towards these ports will be dropped, we have mixed environments with software ports that
> sometimes have traffic (e.g. decapped ARP requests) software forwarded which will stop working.

Yes, you're right. The only solution I can think of is to add a "bool ignore_errors"
to nbp_flags_change, set to true from new_nbp and del_nbp, and to false from the
netlink code.

> The other lesser issue is with the style below, I mean these three calls for each flag are
> just ugly and look weird as you've also noted, since these APIs are internal can we do better?

Doing better would mean allowing nbp_flags_change() to have a bit mask with
potentially more brport flags set, and to call br_switchdev_set_port_flag in
a for_each_set_bit() loop?