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[99.6.134.177]) by smtp.gmail.com with ESMTPSA id z20sm1616532oth.55.2021.01.23.16.56.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 23 Jan 2021 16:56:45 -0800 (PST) Date: Sat, 23 Jan 2021 16:56:43 -0800 From: Enke Chen To: Neal Cardwell Cc: Jakub Kicinski , Eric Dumazet , "David S. Miller" , Alexey Kuznetsov , Hideaki YOSHIFUJI , Netdev , LKML , enkechen2020@gmail.com Subject: Re: [PATCH net] tcp: make TCP_USER_TIMEOUT accurate for zero window probes Message-ID: <20210124005643.GH129261@localhost.localdomain> References: <20210122191306.GA99540@localhost.localdomain> <20210122174325.269ac329@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> <20210123022823.GA100578@localhost.localdomain> <20210122183424.59c716a1@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> <20210123024534.GB100578@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Neal: What you described is more accurate, and is correct. Thanks. -- Enke On Sat, Jan 23, 2021 at 07:19:13PM -0500, Neal Cardwell wrote: > On Fri, Jan 22, 2021 at 9:45 PM Enke Chen wrote: > > > > Hi, Jakub: > > > > On Fri, Jan 22, 2021 at 06:34:24PM -0800, Jakub Kicinski wrote: > > > On Fri, 22 Jan 2021 18:28:23 -0800 Enke Chen wrote: > > > > Hi, Jakub: > > > > > > > > In terms of backporting, this patch should go together with: > > > > > > > > 9d9b1ee0b2d1 tcp: fix TCP_USER_TIMEOUT with zero window > > > > > > As in it: > > > > > > Fixes: 9d9b1ee0b2d1 tcp: fix TCP_USER_TIMEOUT with zero window > > > > > > or does it further fix the same issue, so: > > > > > > Fixes: 9721e709fa68 ("tcp: simplify window probe aborting on USER_TIMEOUT") > > > > > > ? > > > > Let me clarify: > > > > 1) 9d9b1ee0b2d1 tcp: fix TCP_USER_TIMEOUT with zero window > > > > fixes the bug and makes it work. > > > > 2) The current patch makes the TCP_USER_TIMEOUT accurate for 0-window probes. > > It's independent. > > Patch (2) ("tcp: make TCP_USER_TIMEOUT accurate for zero window > probes") is indeed conceptually independent of (1) but its > implementation depends on the icsk_probes_tstamp field defined in (1), > so AFAICT (2) cannot be backported further back than (1). > > Patch (1) fixes a bug in 5.1: > Fixes: 9721e709fa68 ("tcp: simplify window probe aborting on USER_TIMEOUT") > > So probably (1) and (2) should be backported as a pair, and only back > as far as 5.1. (That covers 2 LTS kernels, 5.4 and 5.10, so hopefully > that is good enough.) > > neal