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[176.103.220.4]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-438bd4856d8sm172306495e9.11.2025.01.28.07.18.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jan 2025 07:18:27 -0800 (PST) Date: Tue, 28 Jan 2025 16:18:25 +0100 From: Stefano Brivio To: Eric Dumazet Subject: Re: [net,v3] tcp: correct handling of extreme memory squeeze Message-ID: <20250128161825.339f95ea@elisabeth> In-Reply-To: References: <20250127231304.1465565-1-jmaloy@redhat.com> Organization: Red Hat X-Mailer: Claws Mail 4.2.0 (GTK 3.24.41; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: mPzyRt9j2_uKMPO6gugFXreOVGdi680l_ahBvTOXXK8_1738077508 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: GIMGKFYST6ZKDTA6T6AYWZDNJ35C6LXD X-Message-ID-Hash: GIMGKFYST6ZKDTA6T6AYWZDNJ35C6LXD X-MailFrom: sbrivio@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: jmaloy@redhat.com, netdev@vger.kernel.org, davem@davemloft.net, kuba@kernel.org, passt-dev@passt.top, lvivier@redhat.com, dgibson@redhat.com, memnglong8.dong@gmail.com, kerneljasonxing@gmail.com, ncardwell@google.com, eric.dumazet@gmail.com X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Tue, 28 Jan 2025 16:04:35 +0100 Eric Dumazet wrote: > This so-called 'deadlock' only occurs if a remote TCP stack is unable > to send win0 probes. > > In this case, sending some ACK will not help reliably if these ACK get lost. > > I find the description tries very hard to hide a bug in another stack, > for some reason. Side note: that was fixed meanwhile. Back then, at a first analysis, we thought it was a workaround, but it's the actual fix as we *must* send zero-window probes in that situation, and this commit triggers them: https://passt.top/passt/commit/?id=a740e16fd1b9bdca8d259aa6d37f942a3874425c -- Stefano