linux-kernel - Re: [PATCH v1 1/1] net: neigh: persist proxy config across link flaps

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Message-ID: <CAG88wWYA72sij4iaWowLpawzM7tJdYdHCKQnE0bjndGO74vROw@mail.gmail.com>
Date:   Thu, 15 Dec 2022 12:36:32 -0800
From:   David Decotigny <ddecotig@...gle.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     David Ahern <dsahern@...nel.org>,
        Mahesh Bandewar (महेश बंडेवार) 
        <maheshb@...gle.com>, David Decotigny <decot+git@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        "Denis V. Lunev" <den@...nvz.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Chen Zhongjin <chenzhongjin@...wei.com>,
        Yuwei Wang <wangyuweihx@...il.com>,
        Alexander Mikhalitsyn <alexander.mikhalitsyn@...tuozzo.com>,
        Thomas Zeitlhofer <thomas.zeitlhofer+lkml@...it.at>
Subject: Re: [PATCH v1 1/1] net: neigh: persist proxy config across link flaps

(answer below)

On Thu, Dec 15, 2022 at 11:05 AM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Wed, 14 Dec 2022 22:18:04 -0800 David Decotigny wrote:
> > I don't think this patch is changing that part of the behavior: we still
> > flush the cached nd entries when the link flaps. What we don't remove are
> > the pneigh_entry-es (ip neigh add proxy ...) attached to the device where
> > the link flaps: those are configured once and this patch ensures that they
> > survive the link flaps as long as the netdev stays admin-up. When
> > the netdev is brought admin-down, we keep the behavior we had before the
> > patch.
>
> Makes sense. This is not urgent, tho, right?

Not that kind of urgent.

FTR, in the v2 you suggested to use NUD_PERMANENT, I can try to see
how this would look like. Note that this will make the patch larger
and more intrusive, and with potentially a behavior change for whoever
uses the netlink API directly instead of the iproute2 implementation
for ip neigh X proxy things.

>
> David A, do you agree and should we treat this as a fix with
>
> Fixes: 859bd2ef1fc1 ("net: Evict neighbor entries on carrier down")

Thanks.

>
> added?
>
> Reminder: please bottom post on the list