netdev - Re: [PATCH net-next] net: bridge: switchdev: allow port isolation to be offloaded

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Date:   Thu, 12 Aug 2021 00:52:48 +0300
From:   Ido Schimmel <idosch@...sch.org>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     DENG Qingfang <dqfext@...il.com>, Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <nikolay@...dia.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "moderated list:ETHERNET BRIDGE" <bridge@...ts.linux-foundation.org>,
        "open list:ETHERNET BRIDGE" <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH net-next] net: bridge: switchdev: allow port isolation to
 be offloaded

On Thu, Aug 12, 2021 at 12:45:06AM +0300, Vladimir Oltean wrote:
> On Thu, Aug 12, 2021 at 12:38:56AM +0300, Ido Schimmel wrote:
> > On Wed, Aug 11, 2021 at 09:52:46PM +0800, DENG Qingfang wrote:
> > > Add BR_ISOLATED flag to BR_PORT_FLAGS_HW_OFFLOAD, to allow switchdev
> > > drivers to offload port isolation.
> > >
> > > Suggested-by: Vladimir Oltean <olteanv@...il.com>
> > > Signed-off-by: DENG Qingfang <dqfext@...il.com>
> > > ---
> > >  net/bridge/br_switchdev.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/net/bridge/br_switchdev.c b/net/bridge/br_switchdev.c
> > > index 6bf518d78f02..898257153883 100644
> > > --- a/net/bridge/br_switchdev.c
> > > +++ b/net/bridge/br_switchdev.c
> > > @@ -71,7 +71,8 @@ bool nbp_switchdev_allowed_egress(const struct net_bridge_port *p,
> > >
> > >  /* Flags that can be offloaded to hardware */
> > >  #define BR_PORT_FLAGS_HW_OFFLOAD (BR_LEARNING | BR_FLOOD | \
> > > -				  BR_MCAST_FLOOD | BR_BCAST_FLOOD)
> > > +				  BR_MCAST_FLOOD | BR_BCAST_FLOOD | \
> > > +				  BR_ISOLATED)
> >
> > Why add it now and not as part of a patchset that actually makes use of
> > the flag in a driver that offloads port isolation?
> 
> The way the information got transmitted is a bit unfortunate.
> 
> Making BR_ISOLATED part of BR_PORT_FLAGS_HW_OFFLOAD is a matter of
> correctness when switchdev offloads the data path. Since this feature
> will not work correctly without driver intervention, it makes sense that
> drivers should reject it currently, which is exactly what this patch
> accomplishes - it makes the code path go through the
> SWITCHDEV_ATTR_ID_PORT_PRE_BRIDGE_FLAGS driver handlers, which return
> -EINVAL for everything they don't recognize.

If the purpose is correctness, then this is not the only flag that was
missed. BR_HAIRPIN_MODE is also relevant for the data path, for example.

Anyway, the commit message needs to be reworded to reflect the true
purpose of the patch.

> 
> (yes, we do still have a problem for drivers that don't catch
> SWITCHDEV_ATTR_ID_PORT_PRE_BRIDGE_FLAGS at all, switchdev will return
> -EOPNOTSUPP for those which is then ignored, but those are in the
> minority)