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[2003:c1:4f19:9600:9e6b:ff:fe39:b8a7]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4854a307bc4sm7973655e9.3.2026.03.10.15.34.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Mar 2026 15:34:39 -0700 (PDT) Received: by gandalf.schnuecks.de (Postfix, from userid 500) id 21673302C729; Tue, 10 Mar 2026 23:34:39 +0100 (CET) Date: Tue, 10 Mar 2026 23:34:39 +0100 From: Simon Baatz To: Stefano Brivio Cc: Simon Baatz via B4 Relay , Eric Dumazet , Neal Cardwell , Kuniyuki Iwashima , "David S. Miller" , Jakub Kicinski , Paolo Abeni , Simon Horman , Jonathan Corbet , Shuah Khan , David Ahern , Jon Maloy , Jason Xing , mfreemon@cloudflare.com, Shuah Khan , Matthieu Baerts , Mat Martineau , Geliang Tang , netdev@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, mptcp@lists.linux.dev Subject: Re: [PATCH net-next v3 1/6] tcp: implement RFC 7323 window retraction receiver requirements Message-ID: References: <20260309-tcp_rfc7323_retract_wnd_rfc-v3-0-4c7f96b1ec69@gmail.com> <20260309-tcp_rfc7323_retract_wnd_rfc-v3-1-4c7f96b1ec69@gmail.com> <20260310095806.121d198f@elisabeth> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260310095806.121d198f@elisabeth> Hi Stefano, On Tue, Mar 10, 2026 at 09:58:07AM +0100, Stefano Brivio wrote: > Simon, > > On Mon, 09 Mar 2026 09:02:26 +0100 > Simon Baatz via B4 Relay wrote: > > > [...] > > > > diff --git a/include/linux/tcp.h b/include/linux/tcp.h > > index f72eef31fa23cc584f2f0cefacdc35cae43aa52d..73aa2e0ccd1d7a6314a00c27950b019b62a3851c 100644 > > --- a/include/linux/tcp.h > > +++ b/include/linux/tcp.h > > @@ -316,6 +316,9 @@ struct tcp_sock { > > */ > > u32 app_limited; /* limited until "delivered" reaches this val */ > > u32 rcv_wnd; /* Current receiver window */ > > + u32 rcv_mwnd_seq; /* Maximum window sequence number (RFC 7323, > > + * section 2.4, receiver requirements) > > + */ > > I didn't follow the rest of the discussion but, at this point, what > does this mean for applications (CRIU, passt) dumping/restoring socket > data? Do they have to adapt? I couldn't find this bit of information > anywhere in v3. Based on our discussion, the "Setting the TCP_REPAIR_WINDOW socket option initializes rcv_mwnd_seq" v2 change addresses TCP window restoration. As we said that information about window retraction is not crucial, the window will be restored as "non-retracted", matching prior behavior. Therefore, there is no change to the information that applications need to dump or restore. -- Simon Baatz