From mboxrd@z Thu Jan 1 00:00:00 1970 Received: by passt.top (Postfix, from userid 1000) id B6F865A027A; Fri, 15 Aug 2025 18:10:42 +0200 (CEST) From: Stefano Brivio To: passt-dev@passt.top Subject: [PATCH 0/6] tcp: Fixes for issues uncovered by tests with 6.17-rc1 kernels Date: Fri, 15 Aug 2025 18:10:36 +0200 Message-ID: <20250815161042.3606244-1-sbrivio@redhat.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-ID-Hash: 6WM2AP24UGAUJ3E3YUBLE7GZYB4MWJWP X-Message-ID-Hash: 6WM2AP24UGAUJ3E3YUBLE7GZYB4MWJWP X-MailFrom: sbrivio@passt.top 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 , Paul Holzinger 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: 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(-) -- 2.43.0