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([2001:1620:2777:11:cde9:57f6:17e:8aa5]) by smtp.gmail.com with ESMTPSA id o21sm6349665wmc.17.2019.11.27.04.19.43 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 27 Nov 2019 04:19:43 -0800 (PST) Subject: Re: [PATCH v2] net: ip/tnl: Set iph->id only when don't fragment is not set To: Eric Dumazet , David Miller Cc: yoshfuji@linux-ipv6.org, kuznet@ms2.inr.ac.ru, netdev@vger.kernel.org References: <20191124132418.GA13864@fuckup> <20191125.144139.1331751213975518867.davem@davemloft.net> <4e964168-2c83-24bb-8e44-f5f47555e589@gmail.com> <10e81a17-6b38-3cfa-8bd2-04ff43a30541@gmail.com> From: Oliver Herms Message-ID: <57bf0aa5-9640-bf41-41f1-005a1d5d0b62@gmail.com> Date: Wed, 27 Nov 2019 13:19:42 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 27.11.19 01:28, Eric Dumazet wrote: > > > On 11/26/19 3:32 PM, Oliver Herms wrote: >> Using a simple incrementation here, as with sockets, would solve my problem well enough. >> > > I have to ask : Are you aware that linux is SMP OS ? > > If on a mostly idle host, two packets need a different ID, using a " simple incrementation" > wont fit the need. > > sockets are protected against concurrent increments by their lock. > I know and I'm not going to mess around with TCP. I've double checked and found that for non IP tunnel traffic (UDP, TCP, etc.) the cheap function ip_select_ident_segs() is being used. That is absolutely fine. Nothing to optimize here. For IP tunnels __ip_select_ident is being called. And that one is way more expensive than ip_select_ident_segs(). ip_select_ident_segs() increments a counter (yes, I'm aware it is protected by lock). If somehow __ip_select_ident could be refactored to work in a similar fashion that would solve my problem. Thanks Oliver