From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ot1-f48.google.com (mail-ot1-f48.google.com [209.85.210.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 40CEF3AE1BC for ; Tue, 24 Mar 2026 06:04:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.48 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774332273; cv=none; b=pK+cRNmC+F7NTCveME44mWZ3uN8UcqOoD05Q3D+WGFRgWLsPHYuxPy39TgtzhU+4VaQgevBxgSknjfcOR/5qFW9ZzcL/oP5Qin0RJ8YSuHqGncZEx6eYnUdTIDlnTwrCkCRRtcavquJA4iSgcjOVWkcBL7ITe1XR/UbWiiuH0Kk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774332273; c=relaxed/simple; bh=eYCwzFxY2qGj3pCgqVAMjLFFIbI4v5MvL64DV7JicQ0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=nU231w9oyOyb1ecISaB7rtAxsk1DrEKmTwK+NWDROd4R0Lk0pUx5WQGi7wgX5ZfCkzqQqi4YNXT1944oP/+oOcHdCZJYYgcS3Kbihny4YQCLonBITofQIhBwY14IUH7t3uJ3KN2zYH8+2jD/i1Rddz3/sO0SU4EVUBZHbBd/EbA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=cmL3Jayq; arc=none smtp.client-ip=209.85.210.48 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="cmL3Jayq" Received: by mail-ot1-f48.google.com with SMTP id 46e09a7af769-7d7f92bde91so1939037a34.1 for ; Mon, 23 Mar 2026 23:04:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1774332268; x=1774937068; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=b2bTKYrz6TONuhlNDgy7SEn2xSoQ5Qqb0S20rvcw5Ho=; b=cmL3JayqeggRQV89G8Km3o8QnjpYMytrPcff4Jxqdar2vr0hzREkEgAqy1RlfqsB3y uzagKgFCZspeHJIJfO9xSTkvTxy67i+VvP60inqbFm35IimacAs1nEf7SHhpapWDq6EV pdlWswsgojz22h0PWPxGjVr8aiJENMmvpLab7I1LxcZXi9/iCKmYGBvxHO6bT5mfOzJV 8bKLJJ/LWXKxK+yGSy5arTCHYZtlBFsUQOhJdwtHTV+Ssm1g4eS74bzHvKjzQrrXFMg3 4uRdCOG8AiDhTyAq8/T7igSEO8TUnLwp9hh+iD1GGRKjs8tdmElkxSdV01iEFfyjVXcS zfHA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1774332268; x=1774937068; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=b2bTKYrz6TONuhlNDgy7SEn2xSoQ5Qqb0S20rvcw5Ho=; b=hdidVKBQWFa+SwWejNl/XYK9D5+tPFiYxrKRFOOe9xIZWluB3lgP582gjjNzzmXAiq mcdY77OTNlEQe1dwM872jPA6/dKE+Oc7u+ihYP9IHSMAx9+vUht3qGStUAsy7hSceqVH DbYEvAskcufjxA6NJoD5sd4QH0SsL2dS7SDYyFQskph08jQxPoZvU6WTojOEAxc1Rn33 vH9as/o53SZdZZhzhXo5I8Z2VtcmfB4K8aHQV+N27wC2izHIT+r1HJxYgHVL4FAijJ7y quK4kkc2yPGHGW8o/ouaXAPGxTsEp0kY5G+FHt5555WEbO4gUarmbq4O5Jaj5ZXxruoj +3OA== X-Gm-Message-State: AOJu0Yy3htl3cihH/VXDblczEFFv/4/G4hHBFijPD1D4CKp5xHQnFE3g a9pGwqOAT6lNyEyUigdWGgRnCdhm72kQsx6JUguaYkPQ+0Y1jpBpR1Sz X-Gm-Gg: ATEYQzxQdYSfTgWHbx0mqLtdTtD68d0lf1404wIpT3djcHobD9XdOB8tuNAT1fxaoDn nmrT7J4Dou2zUYgC7tQuvnJ2SL7OaVSH2q9vKUrdFiciOhBN64Jad8+4QaQuymFqyZ4jNFKRdIE PKcvJknq6udgWVUQuPP7rs0gUVZYLKSK8sQ/zgRBXndzWW/7OFYk8uvs1fYL/XP0Uj4XsO5xs5G x8ZkSh+T6UoG1zptvSw2zGST3UWcwMTr0DVig8zUy3H0hpy8gyvoc7VqvVF5almoF1bQsR6LxDp HUNiGtkDhNG6x2wMf3VVDXmOBDreDlERLpHM6Nn1aael9ne/9DY1ZTmCE0ble3aWO18CzolSiLK 9L2yCXxgkK0HSkr0beVw+UwiK69O50UA2FUU7HDwskWR3zsRU96Ec2R1Rm61mU6p95z2sEWS4C5 Du65+IoKRO1k7jnDKfkabvbpbYQLIRk8XDWnaDaJbNcm1sjqJ3DQuEKoyS6gNxqbynx0lecKnqf N6Ep3jG069cAt+sewhg+uKQSF/gTJs45dFvKLP5jw== X-Received: by 2002:a05:6830:6f88:b0:7d7:45eb:4e22 with SMTP id 46e09a7af769-7d7eaffb87cmr9661028a34.26.1774332267560; Mon, 23 Mar 2026 23:04:27 -0700 (PDT) Received: from Atwell-Laptop.. (108-212-132-20.lightspeed.irvnca.sbcglobal.net. [108.212.132.20]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7d7eadcb757sm11429957a34.15.2026.03.23.23.04.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Mar 2026 23:04:27 -0700 (PDT) From: Wesley Atwell To: netdev@vger.kernel.org Cc: linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, davem@davemloft.net, edumazet@google.com, ncardwell@google.com, kuniyu@google.com, dsahern@kernel.org, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, shuah@kernel.org, gmbnomis@gmail.com, Wesley Atwell Subject: [PATCH net-next v2 3/3] selftests: packetdrill: cover scaled rwnd quantization slack Date: Tue, 24 Mar 2026 00:04:10 -0600 Message-ID: <20260324060410.1137199-4-atwellwea@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260324060410.1137199-1-atwellwea@gmail.com> References: <20260324060410.1137199-1-atwellwea@gmail.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add a packetdrill reproducer for the free_space-limited scaled no-shrink quantization case. Grow rcv_ssthresh with in-order data, then queue tiny OOO skbs so receive memory drives raw free_space just below rcv_ssthresh without advancing rcv_nxt. The final ACK reaches the case where raw free_space sits just above 84 scaled units while rcv_ssthresh stays slightly larger. Old code rounds that final free_space value up and advertises 85. With the fix, the ACK stays at 84. This gives fail-before/pass-after coverage for the actual raw free_space bug rather than the separate rcv_ssthresh-limited ALIGN-up behavior. Signed-off-by: Wesley Atwell --- v2: - replace the old rcv_ssthresh-limited sequence with an OOO-memory reproducer for the raw free_space case - drop the follow-on ACK transition and keep the final free_space failure case that proves the bug - drop the IPv4-only restriction after verifying the test passes for ipv4, ipv6, and ipv4-mapped-ipv6 - reword the in-file comments to describe the observed behavior without referring to a removed path as "buggy" .../packetdrill/tcp_rcv_quantization_credit.pkt | 62 ++++++++++++++++++++++ 1 file changed, 62 insertions(+) create mode 100644 tools/testing/selftests/net/packetdrill/tcp_rcv_quantization_credit.pkt diff --git a/tools/testing/selftests/net/packetdrill/tcp_rcv_quantization_credit.pkt b/tools/testing/selftests/net/packetdrill/tcp_rcv_quantization_credit.pkt new file mode 100644 index 000000000000..bb4f63772326 --- /dev/null +++ b/tools/testing/selftests/net/packetdrill/tcp_rcv_quantization_credit.pkt @@ -0,0 +1,62 @@ +// SPDX-License-Identifier: GPL-2.0 + +--mss=1000 + +`./defaults.sh +sysctl -q net.ipv4.tcp_moderate_rcvbuf=0 +sysctl -q net.ipv4.tcp_shrink_window=0 +sysctl -q net.ipv4.tcp_rmem="4096 131072 $((32*1024*1024))"` + +// Exercise the scaled no-shrink path when raw backed free_space, not +// rcv_ssthresh, limits the post-ACK window in __tcp_select_window(). +// +// Grow rcv_ssthresh with in-order data, then queue tiny OOO skbs so receive +// memory drops raw free_space to just over 84 scaled units while the current +// rcv_ssthresh stays slightly larger. The final OOO ACK should keep the +// sender-visible window at 84 rather than reopening it to 85. + +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 + +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 + +0 bind(3, ..., ...) = 0 + +0 listen(3, 1) = 0 + + +0 < S 0:0(0) win 32792 + +0 > S. 0:0(0) ack 1 + +0 < . 1:1(0) ack 1 win 257 + + +0 accept(3, ..., ...) = 4 + + +0 < P. 1:10001(10000) ack 1 win 257 + * > . 1:1(0) ack 10001 + + +0 < P. 10001:11024(1023) ack 1 win 257 + * > . 1:1(0) ack 11024 + + +0 < P. 12024:12025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 + + +0 < P. 13024:13025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 + + +0 < P. 14024:14025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 + + +0 < P. 15024:15025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 + + +0 < P. 16024:16025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 + + +0 < P. 17024:17025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 + + +0 < P. 18024:18025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 + + +0 < P. 19024:19025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 + +// The last tiny OOO skb pushes raw free_space just below rcv_ssthresh +// without crossing the next lower scaled unit. + +0 < P. 20024:20025(1) ack 1 win 257 + * > . 1:1(0) ack 11024 win 84 + +0 %{ assert (tcpi_rcv_wnd >> 10) == 84, tcpi_rcv_wnd }% -- 2.43.0