netdev - Re: [PATCH net-next] vxlan: remove fdb when out interface is removed

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Message-ID: <CAMArcTUxrEP0L0UXbpGrBZ64RFUQQCdzG_JD8QtfKDM=n_zuLQ@mail.gmail.com>
Date:   Mon, 1 Jun 2020 21:04:50 +0900
From:   Taehee Yoo <ap420073@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     Jakub Kicinski <kuba@...nel.org>, Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] vxlan: remove fdb when out interface is removed

On Sat, 30 May 2020 at 08:42, David Miller <davem@...emloft.net> wrote:
>

Hi David,
Thanks a lot for your review!

> From: Taehee Yoo <ap420073@...il.com>
> Date: Wed, 27 May 2020 16:29:50 +0000
>
> > vxlan fdb can have NDA_IFINDEX, which indicates an out interface.
> > If the interface is removed, that fdb will not work.
> > So, when interface is removed, vxlan's fdb can be removed.
> >
> > Test commands:
> >     ip link add dummy0 type dummy
> >     ip link add vxlan0 type vxlan vni 1000
> >     bridge fdb add 11:22:33:44:55:66 dst 1.1.1.1 dev vxlan0 via dummy0 self
> >     ip link del dummy0
> >
> > Before this patch, fdbs will not be removed.
> > Result:
> >     bridge fdb show dev vxlan0
> > 11:22:33:44:55:66 dst 1.1.1.1 via if10 self permanent
> >
> > 'if10' indicates 'dummy0' interface index.
> > But the dummy0 interface was removed so this fdb will not work.
> >
> > Signed-off-by: Taehee Yoo <ap420073@...il.com>
>
> But if someone adds an interface afterwards with ifindex 10 that FDB
> entry will start using it.
>
> I don't know how desirable that is, but if someone is depending upon
> that behavior now this change will break things for them.

I also don't know whether reusing FDBs is a valid way.
But, as you said, this patch may break existing things.
So, I think this patch should be dropped.

Thanks a lot!
Taehee Yoo