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Thu, 13 Feb 2020 15:26:49 +0000 Date: Thu, 13 Feb 2020 16:26:46 +0100 From: William Dauchy To: Nicolas Dichtel Cc: netdev@vger.kernel.org Subject: Re: [PATCH v3 net] net, ip6_tunnel: enhance tunnel locate with link check Message-ID: <20200213152646.GA169249@dontpanic> References: <20200212083036.134761-1-w.dauchy@criteo.com> <20200212210647.GB159357@dontpanic> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: PR0P264CA0067.FRAP264.PROD.OUTLOOK.COM (2603:10a6:100:1d::31) To DB3PR0402MB3914.eurprd04.prod.outlook.com (2603:10a6:8:f::29) MIME-Version: 1.0 Received: from dontpanic (91.199.242.231) by PR0P264CA0067.FRAP264.PROD.OUTLOOK.COM (2603:10a6:100:1d::31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2729.24 via Frontend Transport; Thu, 13 Feb 2020 15:26:49 +0000 X-Originating-IP: [91.199.242.231] X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: fce176ef-8a52-4873-93bb-08d7b099250c X-MS-TrafficTypeDiagnostic: DB3PR0402MB3818: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:6430; X-Forefront-PRVS: 031257FE13 X-Forefront-Antispam-Report: SFV:NSPM;SFS:(10019020)(4636009)(366004)(396003)(136003)(39860400002)(346002)(376002)(199004)(189003)(86362001)(66476007)(66556008)(5660300002)(66946007)(6496006)(52116002)(478600001)(6916009)(1076003)(33656002)(26005)(16526019)(186003)(33716001)(9576002)(316002)(4326008)(8676002)(81156014)(81166006)(9686003)(6666004)(55016002)(956004)(2906002)(8936002);DIR:OUT;SFP:1102;SCL:1;SRVR:DB3PR0402MB3818;H:DB3PR0402MB3914.eurprd04.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;A:1;MX:1; Received-SPF: None (protection.outlook.com: criteo.com does not designate permitted sender hosts) X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: Ji+YFzD7Tm/mEPmwSnScveecHPWHEwhBnMKox/3KXXsach/Pcy1xFxmpXFxLEIdDWhcz3IkvnPBtAOK0Js6tmaIAdzACvpvJ+wanV3lnOAOC3gXA2Fd5BWnhcTXyFJWVMMCDIYG/+BehE2Ts5NqG0MOdSbOKjQIVOZWxu5yeDTLTSVD+VklCkC+G3qT/xJvU7VUIglMe8zYkh5yIfO4s3D1F9kUZVtmq4dzSMZHABuUJMkV5wu69Dg1/7SWeNDFVkTKN5AxnlFdWDIitpYlyT3gpz/vd7ycb7vB8+HPq0b6DFc/DOyTr99mUR5EV0q+oicSco04sLuiKob62hbWb0+WzPxqEZIlwG2iMglLnCb4M5pfSidXhOJxbOOSptBcHb6NPlYftaKzqH754LDqfjLg+e6ImqHc484JxFsJJh6rq9S2AXSaRxfl/PLe/IRHi X-MS-Exchange-AntiSpam-MessageData: 2woSCQiW/OCM1wx205ZzT9lJXhEe6yySf9+PJCODHYMOOcpJBpjWzZVTGem5NVkokXCnoYBgu0mJMdCnYjC5RMJvIictKPyX/vEE1v//AwTPrGQq6QAlSnDxvliDVKzVCBU7/TLpRBZTEqJUw0ujPA== X-OriginatorOrg: criteo.com X-MS-Exchange-CrossTenant-Network-Message-Id: fce176ef-8a52-4873-93bb-08d7b099250c X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Feb 2020 15:26:49.6636 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 2a35d8fd-574d-48e3-927c-8c398e225a01 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: KKAJd0G7GpVoJFWr6FvwWwaJEoGWwkZqQ2RNqpGRld+2wjWAyVWJ26UZSiZV3OlaYcbzQzKIRAfwQ0mfSHp3Dg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB3PR0402MB3818 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Feb 13, 2020 at 10:34:19AM +0100, Nicolas Dichtel wrote: > > mtu = ETH_DATA_LEN; > > if (t->parms.link) { > > tdev = __dev_get_by_index(t->net, t->parms.link); > > if (tdev && tdev->mtu < mtu) > Why this second condition? Why not allowing more than ETH_DATA_LEN (1500)? > ip_tunnels do: > if (tdev) { > > hlen = tdev->hard_header_len + tdev->needed_headroom; > > mtu = min(tdev->mtu, IP_MAX_MTU); > > } > which seems better. I wrongly mixed the two codes in my head as I wanted to take the lowest of the two values; will correct that; sorry for the confusion. > Note also that you patch ip6_tnl_dev_init_gen(), but ip6_tnl_link_config() is > called later and may adjust the mtu. I would suggest to take care of link mtu in > ip6_tnl_link_config(). agreed, I overlooked it. Unsure whether I can put it in CAP_XMIT condition as well. > hard_header_len is not set for ipv4 tunnels, but for ipv6 tunnels: > dev->hard_header_len = LL_MAX_HEADER + t_hlen; > > This is not the real value, I don't think you can calculate the real mtu based > on this. understood, I indeed did not noticed hard_header_len was not set in ip_tunnel. Best, -- William