From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from Chamillionaire.breakpoint.cc (Chamillionaire.breakpoint.cc [91.216.245.30]) (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 414622550C5; Wed, 9 Apr 2025 10:45:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.216.245.30 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744195543; cv=none; b=ujdYMVB7hGpVQMYDkUxCvi98mJ2tLPO5hdjFAGNet7F3wKXys8n4bW35Msd6dozFjMNjXFKUUkPQJ83TFfcL0AwS8ukxZa/OXEVFi0qLGOnRYMmRWAMkhCicHMIoAXiS557hpZTZmOanImIgbyuoW2tr3RlTavqnMXngwjiAuyQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744195543; c=relaxed/simple; bh=Zd42bH/iKPNHGtL2PyAIzxQXMD0Ub6g/t7/nY59Wno4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KElfBFiGs04KQ/6oqFbJS3Q7LpVly5WN4lvL6skkNKNYV9OpKBGRPF0quOXb/l4ATZe/pOtw8LiATVm8jKK029oaeZK/8TMgsGwfiKcLZUh30v0xvFJJ92bY07jnMikYvax0n3AQZzzV1HriIbcrKfh1Zvs5Unh9mfqgrnSSI6g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=strlen.de; spf=pass smtp.mailfrom=strlen.de; arc=none smtp.client-ip=91.216.245.30 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=strlen.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=strlen.de Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1u2Svt-0005gk-4E; Wed, 09 Apr 2025 12:45:25 +0200 Date: Wed, 9 Apr 2025 12:45:25 +0200 From: Florian Westphal To: Yang =?utf-8?B?SHVhamlhbu+8iOadqOWNjuWBpe+8iQ==?= Cc: Florian Westphal , "pablo@netfilter.org" , "kadlec@netfilter.org" , "razor@blackwall.org" , "idosch@nvidia.com" , "davem@davemloft.net" , "dsahern@kernel.org" , "edumazet@google.com" , "kuba@kernel.org" , "pabeni@redhat.com" , "horms@kernel.org" , "netfilter-devel@vger.kernel.org" , "coreteam@netfilter.org" , "bridge@lists.linux.dev" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: =?utf-8?B?562U5aSNOiBbUEFUQ0hdIG5ldDog?= =?utf-8?Q?Expand_headroo?= =?utf-8?Q?m?= to send fragmented packets in bridge fragment forward Message-ID: <20250409104525.GC17911@breakpoint.cc> References: <20250409073336.31996-1-huajianyang@asrmicro.com> <20250409091821.GA17911@breakpoint.cc> <0a711412f54c4dc6a7d58f4fa391dc0f@exch03.asrmicro.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <0a711412f54c4dc6a7d58f4fa391dc0f@exch03.asrmicro.com> User-Agent: Mutt/1.10.1 (2018-07-13) Yang Huajian（杨华健） wrote: > > if (skb_headroom(skb) < ll_rs) > > goto expand_headroom; > > > ... but I'm not sure what the actual problem is. > > Yes, your guess is correct! > > Actual problem: I think it is unreasonable to directly drop skb with insufficient headroom. > > > Why does this need to make a full skb copy? > > Should that be using skb_expand_head()? > > Using skb_expand_head has the same effect. > > Actually, can't you just (re)use the slowpath for the skb_headroom < ll_rs case instead of adding headroom expansion? > > I tested it just now, reuse the slowpath will successed. > But maybe this change cannot resolve all cases if the netdevice really needs this headroom. The slowpath considers headroom requirements, see ip_frag_next(): skb2 = alloc_skb(len + state->hlen + state->ll_rs, GFP_ATOMIC); You should wait for more feedback and then send a v2 tomorrow. Thanks!