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Mon, 18 Aug 2025 10:40:42 -0700 (PDT) Received: from [192.168.188.22] ([80.243.52.133]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-70ba9086433sm56449546d6.24.2025.08.18.10.40.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 18 Aug 2025 10:40:41 -0700 (PDT) Message-ID: <9f68836b-4a5c-4228-9849-6f5103851be3@redhat.com> Date: Mon, 18 Aug 2025 19:40:39 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/6] tcp: Fixes for issues uncovered by tests with 6.17-rc1 kernels To: Stefano Brivio , passt-dev@passt.top References: <20250815161042.3606244-1-sbrivio@redhat.com> From: Paul Holzinger In-Reply-To: <20250815161042.3606244-1-sbrivio@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: opDmlxVRgujom7F23RWY8WpT_HS95jS9fczkafHYzHc_1755538843 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Message-ID-Hash: AFWDVPT2MB4OSJAV2AZ7HG6QPABHD7KP X-Message-ID-Hash: AFWDVPT2MB4OSJAV2AZ7HG6QPABHD7KP X-MailFrom: pholzing@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: Jon Maloy 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: Hi, On 15/08/2025 18:10, Stefano Brivio wrote: > Starting from Linux kernel commit 1d2fbaad7cd8 ("tcp: stronger > sk_rcvbuf checks"), window limits are enforced more aggressively with > a bigger amount of zero-window updates compared to what happened with > e2142825c120 ("net: tcp: send zero-window ACK when no memory") alone, > and occasional duplicate ACKs can now be seen also for local transfers > with default (208 KiB) socket buffer sizes. > > Paul reports that, with 6.17-rc1-ish kernels, Podman tests for the > pasta integration occasionally fail on the "TCP/IPv4 large transfer, > tap" case. > > While playing with a reproducer that seems to be matching those > failures: > > while true; do ./pasta --trace -l /tmp/pasta.log -p /tmp/pasta.pcap --config-net -t 5555 -- socat TCP-LISTEN:5555 OPEN:/tmp/large.rcv,trunc & (sleep 0.3; socat -T2 OPEN:large.bin TCP:88.198.0.164:5555; ); wait; diff large.bin /tmp/large.rcv || break; done > > and a kernel including that commit, I hit a few different failures, > that should be fixed by this series. > > Stefano Brivio (6): > tcp: FIN flags have to be retransmitted as well > tcp: Factor sequence rewind for retransmissions into a new function > tcp: Rewind sequence when guest shrinks window to zero > tcp: Fix closing logic for half-closed connections > tcp: Don't try to transmit right after the peer shrank the window to > zero > tcp: Fast re-transmit if half-closed, make TAP_FIN_RCVD path > consistent > > tcp.c | 170 ++++++++++++++++++++++++++++++++++++++++------------------ > 1 file changed, 118 insertions(+), 52 deletions(-) I applied the series in my test VM and run the reproducer from the podman tests where I noticed the flake. It failed after about 10mins and then when I enabled pasta trace logs and tcpdump captures then it took 208 mins for me to reproduce so it doesn't seem to fix the issue I am seeing. I did send the pasta log/pcap files in private to Stefano for further debugging. -- Paul Holzinger