netdev - Re: [PATCH net-next v2] net, neigh: introduce interval_probe

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Message-ID: <CANmJ_FN6_79nRmmzKzoExzD+KJ5Uzehj8Rw_GQhV0SiBpF3rPg@mail.gmail.com>
Date:   Wed, 25 May 2022 03:13:38 +0800
From:   Yuwei Wang <wangyuweihx@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     davem@...emloft.net, Eric Dumazet <edumazet@...gle.com>,
        roopa@...dia.com, dsahern@...nel.org,
        秦迪 <qindi@...ff.weibo.com>,
        netdev@...r.kernel.org, yuwei wang <wangyuweihx@...mail.com>
Subject: Re: [PATCH net-next v2] net, neigh: introduce interval_probe_time for
 periodic probe

On Wed, 25 May 2022 at 02:07, Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Tue, 24 May 2022 17:32:57 +0200 Daniel Borkmann wrote:
> > Right, maybe we could just split this into two: 1) prevent misconfig (see
> > below), and 2) make the timeout configurable as what Yuwei has. Wdyt?
> >
> > diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> > index 47b6c1f0fdbb..54625287ee5b 100644
> > --- a/net/core/neighbour.c
> > +++ b/net/core/neighbour.c
> > @@ -1579,7 +1579,7 @@ static void neigh_managed_work(struct work_struct *work)
> >          list_for_each_entry(neigh, &tbl->managed_list, managed_list)
> >                  neigh_event_send_probe(neigh, NULL, false);
> >          queue_delayed_work(system_power_efficient_wq, &tbl->managed_work,
> > -                          NEIGH_VAR(&tbl->parms, DELAY_PROBE_TIME));
> > +                          max(NEIGH_VAR(&tbl->parms, DELAY_PROBE_TIME), HZ));
> >          write_unlock_bh(&tbl->lock);
> >   }
>
> FWIW that was my reaction as well. Let's do that unless someone
> disagrees.

I agree too, so there will be as following parts:
1) prevent misconfig by offering a minimum value
2) separate the params `INTERVAL_PROBE_TIME` as the probe interval for
`MANAGED` neigh
3) notify the change of `INTERVAL_PROBE_TIME` and set the driver poll interval
according to `INTERVAL_PROBE_TIME` instead of `DELAY_PROBE_TIME`

I still have doubt about whether we need part 3, or if exist this scenario:
- the NIC offloading the data plane.
- the driver needs periodically poll the device for neighbours activity

May I ask for further explanation?

Thanks,
Yuwei Wang