From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 5147229B789; Tue, 17 Mar 2026 02:55:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773716101; cv=none; b=fYyG4RpDjQUXwteFcsY+iAibHeTBlGQlGfpOLvgOiop2Zg5Fzk4UErKnSb9gNVEzR0w9bXbZw4OjtOSbuB5hRum34MkIdLcgN9q07rkXtY1TINjpTb2fNn7ADD8J5GwKxX5pFie6X2hYPtYg7BrRtC1Mqf90PP1iDygLOSdeX5k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773716101; c=relaxed/simple; bh=Z4eVxfTOXAxJwAikqB+iCh+6xG7rIQq8g2sRZSUuTYI=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=UyNHabjAzFf+eouUwiedZQdOWleBlBEvOJ2Dvah26i/TFTkakVppml/pLmn4Sur/uXFE23lpEaDrMR5NCT3DoL8pSxCSrW5F18EXtVF5KqyAlu+WxkQIO9rMzfMyPtsgwOmlxrDQy/QRxgnMweYG/bYwKmKoh6PVH+wP1XKkPLM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YBQNQjbG; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YBQNQjbG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BF29AC19421; Tue, 17 Mar 2026 02:55:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773716101; bh=Z4eVxfTOXAxJwAikqB+iCh+6xG7rIQq8g2sRZSUuTYI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=YBQNQjbGH/rHtnt4VtCqjLpWi41SnGKDngcFGR6hDu9osRiywbA5eXhUH6bB/Nl1f rCY8u22qfp++uf630TW0TdnXjEJATK3ZLfamlrYV09X0cf4Zk9OSi/JMD/Ik0woMA2 WeacdpsIo/Fx+Wkd14ZXejsfJUmaet8ilFUgDpH5jdN0waTDcwF/Xhg751X8rzIM9z 7HfH8Z9rEMXf6PbBAk9NWB3lcY7PPv1I+SkgLjZNIhsNMs9P8N38MHuS1Fjocv/S44 USat5aDRUGfSFR5T9c9bptgO/HmkhgAnQXtdau/Qm9TPSntGaF1IwgXuXTA/oLs1De KPeXhh4HtOruQ== Date: Mon, 16 Mar 2026 19:54:59 -0700 From: Jakub Kicinski To: Qingfang Deng Cc: linux-ppp@vger.kernel.org, James Chapman , "David S. Miller" , Eric Dumazet , Paolo Abeni , Simon Horman , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net] l2tp: ppp: use max L2TP header size for PPP channel hdrlen Message-ID: <20260316195459.6e4d6d9b@kernel.org> In-Reply-To: <20260313034732.209792-1-dqfext@gmail.com> References: <20260313034732.209792-1-dqfext@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 13 Mar 2026 11:47:31 +0800 Qingfang Deng wrote: > chan.hdrlen is read once at channel registration by > ppp_register_net_channel(), and used to set the PPP net device's > hard_header_len. It was set to PPPOL2TP_L2TP_HDR_SIZE_NOSEQ (6), which > is 4 bytes too small if sequence numbers are later enabled via > setsockopt(PPPOL2TP_SO_SENDSEQ), causing unnecessary skb reallocations > on the TX path. If the main effect of this patch is that we avoid reallocations I think this is an optimization and should go to net-next? If there's more to it please explain in the commit msg a bit more. -- pw-bot: cr