netdev - Re: [PATCHv2 net] ipv6/route: should not update neigh confirm time during PMTU update

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Message-ID: <20191203101536.GJ18865@dhcp-12-139.nay.redhat.com>
Date:   Tue, 3 Dec 2019 18:15:37 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, ja@....bg, marcelo.leitner@...il.com,
        dsahern@...il.com, edumazet@...gle.com
Subject: Re: [PATCHv2 net] ipv6/route: should not update neigh confirm time
 during PMTU update

On Mon, Dec 02, 2019 at 06:47:04PM -0800, David Miller wrote:
> From: Hangbin Liu <liuhangbin@...il.com>
> Date: Tue,  3 Dec 2019 10:11:37 +0800
> 
> > Fix it by removing the dst_confirm_neigh() in __ip6_rt_update_pmtu() as
> > there is no two-way communication during PMTU update.
> > 
> > v2: remove dst_confirm_neigh directly as David Miller pointed out.
> 
> That's not what I said.
> 
> I said that this interface is designed for situations where the neigh
> update is appropriate, and that's what happens for most callers _except_
> these tunnel cases.
> 
> The tunnel use is the exception and invoking the interface
> inappropriately.
> 
> It is important to keep the neigh reachability fresh for TCP flows so
> you cannot remove this dst_confirm_neigh() call.
> 
> Instead, make a new interface that the tunnel use cases can call into
> to elide the neigh update.
> 
> Yes, this means you will have too update all of the tunnel callers
> into these calls chains but that's the price we have to pay in this
> situation unfortunately.

Oh, I got what you mean now. thanks for the explain. I will see how
to do this.

Thanks
Hangbin