From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from nbd.name (nbd.name [46.4.11.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6FDBE27465B; Tue, 15 Jul 2025 11:35:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=46.4.11.11 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752579323; cv=none; b=NX3+UkjRUBAN3s6JI7p1RUia2bqlJHqUWrXDQ+VFJVGcZOdJxF3bV+DZkjvBX2qCYht6Ie7GRbYBFpgdMa5k6HaRLgztk0dNcdp4Y6LLj2gp/0UMUBKnHGY84RL5ivQXWu4sffwghi7jcaTAlz4Zt5CKV0m2HJWa9j/fTmqxQx8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752579323; c=relaxed/simple; bh=THkSLQGTMsX7Fdbhve8y28Aa2BhuUAw66zvj6IMFz7I=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Qe+ytQUaoTDWIYbYdqY8oyfSHzrrKGLoLA7pJzELW34grHwiw+YXJoflV3x6RMmxTpmwbpTNDJy2xXI9m5uc0iWhjZJMeR55soLeRkMAabnKt8Twa2Ntc8xWtFsoL2wLmj85jM9+ZsEcjFdGPv7NS5G22VtLTIIZQMRNoPyeD28= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=nbd.name; spf=none smtp.mailfrom=nbd.name; dkim=pass (1024-bit key) header.d=nbd.name header.i=@nbd.name header.b=nXC/W3HS; arc=none smtp.client-ip=46.4.11.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=nbd.name Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=nbd.name Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=nbd.name header.i=@nbd.name header.b="nXC/W3HS" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=nbd.name; s=20160729; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:From: References:Cc:To:Subject:MIME-Version:Date:Message-ID:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=JTAXuxhoCTpmlrj2PLz1NIWHz+APNjNKXFIRCUVGU2g=; b=nXC/W3HSEvfvTE7dklSO76sEZg gwE0DWhX8zW3M6T+UctzJdi3n2gKu8g4fiXfwR7jbMgzlqjuZoW07cb33TqcOgqTNRIoJbZUH2AaK IlPx44BbBahwNzrA1XBrAPNJiQqwvlPn27dzoK1E7BXW0OseQvs6CDm71FuckxP24tHc=; Received: from p5b2062ed.dip0.t-ipconnect.de ([91.32.98.237] helo=nf.local) by ds12 with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.96) (envelope-from ) id 1ubdwH-00CCXu-1i; Tue, 15 Jul 2025 13:35:13 +0200 Message-ID: Date: Tue, 15 Jul 2025 13:35:12 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net] net: fix segmentation after TCP/UDP fraglist GRO To: Willem de Bruijn , netdev@vger.kernel.org, Eric Dumazet , Neal Cardwell , Kuniyuki Iwashima , "David S. Miller" , David Ahern , Jakub Kicinski , Paolo Abeni , Simon Horman , Willem de Bruijn , Richard Gobert Cc: linux-kernel@vger.kernel.org References: <20250705150622.10699-1-nbd@nbd.name> <686a7e07728fc_3aa654294f9@willemb.c.googlers.com.notmuch> Content-Language: en-US From: Felix Fietkau Autocrypt: addr=nbd@nbd.name; keydata= xsDiBEah5CcRBADIY7pu4LIv3jBlyQ/2u87iIZGe6f0f8pyB4UjzfJNXhJb8JylYYRzIOSxh ExKsdLCnJqsG1PY1mqTtoG8sONpwsHr2oJ4itjcGHfn5NJSUGTbtbbxLro13tHkGFCoCr4Z5 Pv+XRgiANSpYlIigiMbOkide6wbggQK32tC20QxUIwCg4k6dtV/4kwEeiOUfErq00TVqIiEE AKcUi4taOuh/PQWx/Ujjl/P1LfJXqLKRPa8PwD4j2yjoc9l+7LptSxJThL9KSu6gtXQjcoR2 vCK0OeYJhgO4kYMI78h1TSaxmtImEAnjFPYJYVsxrhay92jisYc7z5R/76AaELfF6RCjjGeP wdalulG+erWju710Bif7E1yjYVWeA/9Wd1lsOmx6uwwYgNqoFtcAunDaMKi9xVQW18FsUusM TdRvTZLBpoUAy+MajAL+R73TwLq3LnKpIcCwftyQXK5pEDKq57OhxJVv1Q8XkA9Dn1SBOjNB l25vJDFAT9ntp9THeDD2fv15yk4EKpWhu4H00/YX8KkhFsrtUs69+vZQwc0cRmVsaXggRmll dGthdSA8bmJkQG5iZC5uYW1lPsJgBBMRAgAgBQJGoeQnAhsjBgsJCAcDAgQVAggDBBYCAwEC HgECF4AACgkQ130UHQKnbvXsvgCgjsAIIOsY7xZ8VcSm7NABpi91yTMAniMMmH7FRenEAYMa VrwYTIThkTlQzsFNBEah5FQQCACMIep/hTzgPZ9HbCTKm9xN4bZX0JjrqjFem1Nxf3MBM5vN CYGBn8F4sGIzPmLhl4xFeq3k5irVg/YvxSDbQN6NJv8o+tP6zsMeWX2JjtV0P4aDIN1pK2/w VxcicArw0VYdv2ZCarccFBgH2a6GjswqlCqVM3gNIMI8ikzenKcso8YErGGiKYeMEZLwHaxE Y7mTPuOTrWL8uWWRL5mVjhZEVvDez6em/OYvzBwbkhImrryF29e3Po2cfY2n7EKjjr3/141K DHBBdgXlPNfDwROnA5ugjjEBjwkwBQqPpDA7AYPvpHh5vLbZnVGu5CwG7NAsrb2isRmjYoqk wu++3117AAMFB/9S0Sj7qFFQcD4laADVsabTpNNpaV4wAgVTRHKV/kC9luItzwDnUcsZUPdQ f3MueRJ3jIHU0UmRBG3uQftqbZJj3ikhnfvyLmkCNe+/hXhPu9sGvXyi2D4vszICvc1KL4RD aLSrOsROx22eZ26KqcW4ny7+va2FnvjsZgI8h4sDmaLzKczVRIiLITiMpLFEU/VoSv0m1F4B FtRgoiyjFzigWG0MsTdAN6FJzGh4mWWGIlE7o5JraNhnTd+yTUIPtw3ym6l8P+gbvfoZida0 TspgwBWLnXQvP5EDvlZnNaKa/3oBes6z0QdaSOwZCRA3QSLHBwtgUsrT6RxRSweLrcabwkkE GBECAAkFAkah5FQCGwwACgkQ130UHQKnbvW2GgCeMncXpbbWNT2AtoAYICrKyX5R3iMAoMhw cL98efvrjdstUfTCP2pfetyN In-Reply-To: <686a7e07728fc_3aa654294f9@willemb.c.googlers.com.notmuch> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 06.07.25 15:45, Willem de Bruijn wrote: > Felix Fietkau wrote: >> Since "net: gro: use cb instead of skb->network_header", the skb network >> header is no longer set in the GRO path. >> This breaks fraglist segmentation, which relies on ip_hdr()/tcp_hdr() > > Only ip_hdr is in scope. > > Reviewing TCP and UDP GSO, tcp_hdr/transport header is used also > outside segment list. Non segment list GSO also uses ip_hdr in case > pseudo checksum needs to be set. > > The GSO code is called with skb->data at the relevant header, so L4 > helpers are not strictly needed. The main issue is that data will be > at the L4 header, and some GSO code also needs to see the IP header > (e.g., for aforementioned pseudo checksum calculation). I just spent some time reviewing the code in order to understand how to fix it properly, and I still don't fully understand what you wrote above, especially the part related to "Non segment list GSO". The issue that I'm trying to fix is that the skb network header is wrong for all skbs stored in the frag_list of the first skb. The main skb is fine, since the offsets are handled by the network stack. For all the extra fragment skbs, the offsets are unset because we bypassed the part of the stack that sets them. Since non-segment-list GSO skbs don't carry extra frag_list skbs, I don't see how they can share the same issue. If I misread what you wrote, please point me at the relevant code context that I'm missing. Thanks, - Felix