From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-dl1-f53.google.com (mail-dl1-f53.google.com [74.125.82.53]) (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 A241E18FDBD for ; Sun, 11 Oct 2026 11:16:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.82.53 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791717375; cv=none; b=h/8VXXx+YmeMlSQP0CGfWh4F55VLiD9M/b8bSkst6aLyITkvgKNbVbyuLFesmj2OsAYAQplA+uUGMlzOWNjM1qL+gwIyTD39rgFLHDPZVQRx2A8r0U47FMj4rYIpPpUg5Awpc/vdB44cOX2kTumZkU5U3iinczh3fGuZNhu8nnM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791717375; c=relaxed/simple; bh=5n2fjF0VbSmI6/85OVGLV52tja4i00OrgxTy09Gvdc8=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=uXJaK7VZj5gzIhgjc+B4WvYypv2ZjqBu4z0cw1tdywa19kpfDQJxgUKbfRpSsizrz2NSEc37skURv31AZnKjoXRpPaJPylRXy4Q3ZXlCbNc18tHDmJjD+Do0wMVgy38dmOcHZEyVZD/6GTQPfOHQRlWHzK0Z93MpV7xkacW7+gY= 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=abh822HC; arc=none smtp.client-ip=74.125.82.53 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="abh822HC" Received: by mail-dl1-f53.google.com with SMTP id a92af1059eb24-15354aa70e8so65657c88.1 for ; Sun, 11 Oct 2026 04:16:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1791717374; x=1792322174; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to:content-type; bh=hwfQOboJrE1I9YMyi9xdPhuJ4m7VM518y+XKlBP1o8Q=; b=abh822HCl4O1ZJZh9w1kQWDsGNTdmgVoM8l64QDlRJhzy5nxkHRDixh7QBVCWefxkE hkyiHciDpK7p1g6weKgjwa31NuGh6Aox3YadA8K2IBfcYwP2Og0fVtJ2ak0EEyncQDNR ND5Q3sgArh8I/jW1f64yu0pVMQOyIddhxNaz48VoRnB6BNqe+Zb4/QcZCBk8+LkDX00m 2S1RCC91vRw29lPKdKBZ516jvwMj9dF+8mrLzLXmJ66ygswpiyIQLXy6oiVGbUrQeYEF intz7SngZE0kX0KKQOhLZLujL0M+yE1KVRhmbRE8hqaUReQhB2dLYpatY1optBFGvp+I 2Qeg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1791717374; x=1792322174; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=hwfQOboJrE1I9YMyi9xdPhuJ4m7VM518y+XKlBP1o8Q=; b=adjeCMzzvZVHIQy8IRT85rX8VhKnvdiO3H16U1YS5Yn6Y+rItvn7pgOXXgYtn2326i /ZVVOIQ5fB115CSGOUYS2NiK+fG2YKKWC4VRZoIXeNOrmHcuHYkNLLAAWLRrRByomDXZ F19I9ENRgO1kQL4rHO39V6UYQcmB0T6T6LE9gCs89yPtp4WBToNtCz5+uNxdndYEJPvu ewaMt+jwCo9wzKlJbjoo/6CKwctD6SepMifABT2O27TVxk2FTNpGx9Ct16C17JRe0vH1 HmufZLEZnK5ZgsHCTMpj/n7Lc7QNXoOYssvC6uK34mWXkfn58C97qiBCB3ZKgpA0LWl0 0/Vw== X-Forwarded-Encrypted: i=1; AKwUvBxNFewBnnb3ABNkNI28RcY4McKxWN35lUb5lI1HuU2+anbpSYX01MiCUnsg51cF1mHAcuOVimw=@vger.kernel.org X-Gm-Message-State: AFq9FYLZhiGK9cD5sPsC3+NSjgsoX9l2Z/CQqNd2X2Mwa2X7GGYCUT7G eqeY4RNWIpIRR57lhDwF1cks741bpcQkxnSZJr9xahU9KZdHCJjYv4se X-Gm-Gg: AYBFou0oTE2gND7YvH5Req7HbCrGo96TmwGo+VsMF0lTN4HzDCZm+IgVNp2Dm8Mb2AK MaTQiXUBNRwv1zqfx4jgK/Hf1ixCk6s9d31MTYMuKQhHqfmttjFlsEaZCwRKZ+mly880jLYakZ9 VnwHUFUeDl1q3kxiUVFfeVdxznSh8JThYGUisTto/RrdBYsBEaa9HjYniR1iN5KQPLHvLD2Hyao 9deRRr+ZL4WWcT3C+dXtMiUiA3diLcrwFz0vPV063eKYSIF9Wr9KdUkNs0rTowU2THC+b1ZrlYc r/M/FsomLZf7v4i/KFbw2jydN4A1fUn5E1JGWYkMD328HHOEuR8b3uRBlKoSi9ZbFe9nDk1btfb qeoNxy0Ky3abN975EA6zz9RPQrIaQ00QYERgaDqOqzFdmhtZLz8ujzfFVdlnn+SmS0RyGyvShCH CDuanvHVoGuHpfc915q1tCACaFPzYUedYUxnalJs457UxrCnayZZSMpJ9vO7I5GrO74la7maDxO 4Xfi3iTKKviN78eLi4IyUotE7r0Zd4HAoyX8W8E4MyJ03V3mVol8hnLxbj8E7d9ObC+Ke5MyaQv 6+yUg1ezUz/QEV95k572+COLFjIORmkY8rdMmB26RqnLnu2bDvGllrPmejdSE9gG1HheWboL1vN TO21dvOXlw0g+piWOS/A5S9Esh7mWcSKOX/1agYOFAX6N+a8UAbV+DYIKKj+hMPOMzw== X-Received: by 2002:a05:701b:240d:b0:144:eb46:c3f with SMTP id a92af1059eb24-16a572659bamr10847616c88.2.1791717373401; Sun, 11 Oct 2026 04:16:13 -0700 (PDT) Received: from FT6N242TWK ([223.181.119.248]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-169a6021e49sm20851347c88.20.2026.10.11.04.16.09 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sun, 11 Oct 2026 04:16:12 -0700 (PDT) From: Shashank Mohan Jain To: Eric Dumazet , Neal Cardwell , Jakub Kicinski , Paolo Abeni , "David S. Miller" Cc: Kuniyuki Iwashima , Simon Horman , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH net-next 0/2] tcp: keep the route window on the SYN when SO_RCVBUF is set before connect Date: Sun, 11 Oct 2026 16:46:04 +0530 Message-ID: <20261011111606.14753-1-jain.sm@gmail.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit v1 was a single [PATCH net] with only the fix. Eric Dumazet pointed out that the changelog overstated the effect (TCP_WINDOW_CLAMP does not persist past the first data segments), that "no window scaling" was inaccurate (the option is still sent, with a shift of 0), and asked for a packetdrill test and for the series to target net-next. This v2 rewrites the changelog accordingly, leads with the common SO_RCVBUF-before-connect / listener case, adds a packetdrill test, and is based on net-next. Patch 1 is the fix: setsockopt(SO_RCVBUF) must not write tp->window_clamp while the socket is in TCP_CLOSE or TCP_LISTEN, so that tcp_connect_init() and tcp_openreq_init_rwin() still apply the route window metric (RTAX_WINDOW) and the defaults to the SYN / SYN-ACK window and window scale. Patch 2 adds a packetdrill test: with "window 4096" on the route to the peer and SO_RCVBUF set before connect(), the SYN must advertise the route-clamped window and window scale 0. On an unpatched net-next kernel the SYN carries win 65535, wscale 5; with patch 1 it carries win 2920, wscale 0. Changes since v1 (single [PATCH net]): - changelog: say the patch restores the SYN/SYN-ACK window and window scale, not a persistent clamp; note that since a2cbb1603943 tcp_measure_rcv_mss() recomputes window_clamp from sk_rcvbuf anyway. - changelog: "wscale 0 (option still sent, shift 0)" instead of "no window scaling"; lead with the SO_RCVBUF-before-connect / listener case. - add the packetdrill selftest (patch 2). - retarget from net to net-next. Shashank Mohan Jain (2): tcp: don't set window_clamp from SO_RCVBUF before the socket is connected selftests/net/packetdrill: test SO_RCVBUF before connect keeps route window net/ipv4/tcp.c | 8 ++++++ .../tcp_rcvbuf_before_connect_window.pkt | 27 +++++++++++++++++++ 2 files changed, 35 insertions(+) create mode 100644 tools/testing/selftests/net/packetdrill/tcp_rcvbuf_before_connect_window.pkt base-commit: d8674294aefef02266c4d47ad10131f1bffbe534 -- 2.43.0