netdev - Re: [PATCH net] tcp: fix mid stream window clamp.

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Message-ID: <829107c3e007af0b0e040748f39873d838785dce.camel@redhat.com>
Date: Tue, 28 Nov 2023 09:59:34 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Neil Spring <ntspring@...a.com>, Eric Dumazet <edumazet@...gle.com>, 
	Neal Cardwell <ncardwell@...gle.com>, Wei Wang <weiwan@...gle.com>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "David S. Miller"
	 <davem@...emloft.net>, David Ahern <dsahern@...nel.org>, Jakub Kicinski
	 <kuba@...nel.org>, David Gibson <david@...son.dropbear.id.au>
Subject: Re: [PATCH net] tcp: fix mid stream window clamp.

On Mon, 2023-11-27 at 22:59 +0000, Neil Spring wrote:
> 
> Would the following address the concern?  
> 
> tp->rcv_ssthresh = min(max(tp->rcv_ssthresh, tp->rcv_wnd), tp-
> >window_clamp);
> 
> (that is, rcv_sshthresh must be no greater than window_clamp, but
> otherwise it can keep the larger of its current value or the last
> advertised window.)
> 
> I believe this addresses both problem cases (transient tiny clamp;
> closed window when clamping) and passes (slightly less picky)
> packetdrill tests.

Note that the above is basically the patch I submitted (it yields the
same values).

Yes, it addresses the issue.

But it does not address Eric's concerns reported in this thread.

It's unclear to me if the more involved approach proposed here:

https://lore.kernel.org/netdev/ebb26a4a8a80292423c8cfc965c7b16e2aa4e201.camel@redhat.com/

would be ok?

Thanks!

Paolo