From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yx2-f12.google.com (mail-yx2-f12.google.com [74.125.224.140]) (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 3AC262E6CB8 for ; Mon, 21 Sep 2026 21:07:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.224.140 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790024833; cv=none; b=VJSY+BLrEt3Xbky2ndbSCtjMSTx8xCSuUhzdxCdH/2jmZQxXoMUNhugfvEnIVekWqao4hbsAcv8SGYisO0O1KVmdjbzIt3bf7W5Ya5bSSmdz6DwNdQ//Sm4ZmeTm6Ol3nCRVFFkGNWiWxvGsy/ek5l4szgxkxUmjXHbnzEJiDiE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790024833; c=relaxed/simple; bh=Qgg2jfj8I0DSyFxrZZfdeMmjANs6OmQ1w2AFzDFHIkc=; h=Date:From:To:Cc:Message-ID:In-Reply-To:References:Subject: MIME-Version:Content-Type; b=el1EOkOqHIt9rJOzfRNthnkzmTzCyvCFqf23mDbHH5ShnCEXKAEu9KtLSuijSdRiokU66YdgzFbG2kgHw50apPQwoc9pHMmc/OmpvtcTG3ikvdR/SxBQyEznwQ2NgdSlI6XdsTKx2ZqZrSAb0HaH9wETbDr+Ekdwr8eLYArUS3c= 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=NtrDsGCP; arc=none smtp.client-ip=74.125.224.140 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="NtrDsGCP" Received: by mail-yx2-f12.google.com with SMTP id 00721157ae682-85d43ac8d1eso26564547b3.2 for ; Mon, 21 Sep 2026 14:07:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1790024831; x=1790629631; darn=vger.kernel.org; h=content-transfer-encoding:content-type:mime-version:subject :references:in-reply-to:message-id:cc:to:from:date:from:to:cc :subject:date:message-id:reply-to:content-type; bh=Ii7Gh4oAdaXOZZuSQ3QehEmb1DVYOhw82tgsap0BzQA=; b=NtrDsGCPzDJepIIUUHCtjsOJTdE5NN+uWxhGyBFqRWbtpz41KXEHDwtswAclArYI6l askW+n+upTks73rZEzWxpGErQAPiePurX0SJ9/t6MuWzTBoHsG42HzgCrMfS8NvL+Y3b YnfEmOhWijpwfmQZbtApwmxe7O7lpsuQSzfuvQaYJog/A9d7rgmRio7l3vuImos0SXQi 1feZaDfOLbFkGbMhh5UWdDcS+u5v87/68ho+8crZOGJ5IGYHhXPtZ9pZ57z7madUZriC HbRwiz20DGpSc75ha7dzC1YUNQpsw6J8uFvnxmwB+Mkq2EtwpJlLF8bIju2r0DjQ+jiL sfUw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790024831; x=1790629631; h=content-transfer-encoding:content-type:mime-version:subject :references:in-reply-to:message-id:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=Ii7Gh4oAdaXOZZuSQ3QehEmb1DVYOhw82tgsap0BzQA=; b=KcgmtJB1QqH7+mKsQ6ONkW4oT7vaPxomPdmGRXtfqaFS/+mK3b5UlKWFLkh3/UYvXE aw2g4vHiwdTKgrN5qVPnnvRxa/n7/XYmkj/fQuxxwQG32ACJ++eMe8+opmq6Nz96114w kj32AGLtupcePepwQHApC1yFD+7tRLeB2mwgLC9TwrnqsG5zcFeyIJom3g7QykEi5gMG 5GPVXpNlZ2FiUJbDc7QbHNRQ3Cac65EZL168ZEYenK/LKhxH6DYI71Lo+K/bo7ephPFB Vft0OVzDrk3x6dPgJO0j96SFWYZypVDRTIWPQO7d/ETkxO16RQX5zWDfIA4iSn4tdpK0 HjXg== X-Forwarded-Encrypted: i=1; AKwUvBzyfeuHwI5rUHd4N3MoHyoUetvWJPaYyAW03xp3N7EFC9BF1URPpmhz1Eq7Qrs5NrjUnyUixlE=@vger.kernel.org X-Gm-Message-State: AFuF++luSazjUPsgtJffo/FXOXs0vy6u1ZxmWHW3g1uCSeOcuag5z1lu JScUxMAhVCyAZk472VXEL2+dN+A/YUv3jfMaGy4mjiAStZxP2XodCRUj X-Gm-Gg: AYBFou0urOXz4p2HVAuHBBWtzl8b1rctzwViyQbXzx/OvGbSU/q3gIlx5s1d78g+fW4 9aodPT9oN1o26rZKbaki3IR9z0FcD7gIb6vqhvcq5zWPiy5UatgWGyNsJIOzCxd+qemeA89AWxA BmWTyiwGn5qFOdczzGYKLb66kEq+jjSWqXxTs2u7JKX561yZS8Xd3B9uM82RMymYfoVXHyaXi1t a9mOxXReFMfsRXW3yH25Y3ESYYpwT+RcLdMT8jLsXPnbkejhhiRo9KPiklLp/hWKLtXNU5ukhKU z5bAqPEVXE9S/ppKJpU60CSZkQHZy+KPV8blQaqGSlmh2Vgboc0oQfEFfJebgpuuahxZ2OIISvk K+bicSlv+D5gBltQNHTWAAzvQ8JFEv8XcsJicZTL1uKNOmsHLNno7D48YTl/KWuNLw8KMF4EM0x PLwirwgVLCoZe39qIOPhj6pCrBE6T0JUCJWMiJ2Ot7Y3kPZPzw5SNvPfEpLNXys8buhgpczFRyz TFEpwHUKqEDYnuhK0WTv7zTkcX0Wbbd6e6V4JlOTFWyjViGEeKL X-Received: by 2002:a05:690c:6e85:b0:884:c81e:f868 with SMTP id 00721157ae682-8a253faf0eemr1790997b3.13.1790024830574; Mon, 21 Sep 2026 14:07:10 -0700 (PDT) Received: from gmail.com (111.46.245.35.bc.googleusercontent.com. [35.245.46.111]) by smtp.gmail.com with ESMTPSA id 00721157ae682-8a23dea35fasm1439557b3.27.2026.09.21.14.07.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Sep 2026 14:07:09 -0700 (PDT) Date: Mon, 21 Sep 2026 17:07:09 -0400 From: Willem de Bruijn To: Wang Zhan , netdev@vger.kernel.org, Willem de Bruijn Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, keyong.sun@smartx.com, Ilya Maximets , Aaron Conole , Eelco Chaudron , dev@openvswitch.org, Wang Zhan , Andrew Lunn , Jason Wang , Neal Cardwell , Kuniyuki Iwashima , Alice Mikityanska Message-ID: In-Reply-To: <20260920131231.3610688-1-wang.zhan@smartx.com> References: <20260918084651.3022878-1-wang.zhan@smartx.com> <20260918084651.3022878-3-wang.zhan@smartx.com> <20260920131231.3610688-1-wang.zhan@smartx.com> Subject: Re: [PATCH net-next v2 2/4] net: gso: support bounded TCP segmentation Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Wang Zhan wrote: > On Sat, 19 Sep 2026 11:35:17 -0400 Willem de Bruijn wrote: > > > - struct sk_buff *segs = __skb_gso_segment(skb, features, false); > > > + struct sk_buff *segs; > > > struct sk_buff *next; > > > + segs = __skb_gso_segment(skb, features, false, 0); > > > > irrelevant? > > Not unrelated: with the extra argument that line is 82 columns, so the > initializer moved to its own line. The call itself is unchanged. > > > > + unsigned int max_segs = SKB_GSO_CB(head_skb)->max_segs; > > > > could this be computed inside skb_segment, rather than having to be > > passed through SKB_GSO_CB. I haven't checked, but it would simplify. > > I tried it: https://github.com/zwtop/linux/pull/3 > > It does read better, but whether to resegment is the caller's choice: the > qdiscs strip the GSO bits to get one packet per segment (sch_netem.c:443), > and a device-derived limit groups that output instead - which sch_netem then > drops, because skb_checksum_help() on the first segment rejects a GSO skb > (sch_netem.c:538, net/core/dev.c:3626). The features cannot tell the two > cases apart either: gso_features_check() clears the same bits for an > over-limit skb (net/core/dev.c:3843). > > So the bound stays an input from the caller. Somewhat tangential, but an entirely different practical approach could be to disable BIG-TCP when such a patch from BIG-TCP capable to non-capable device is encountered.