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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , David Ahern , Simon Horman , Kuniyuki Iwashima , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Xuanqiang Luo Subject: Re: [PATCH net-next v3 2/2] ipv4: snapshot dst.dev in ip_rt_send_redirect() and ip_rt_get_source() Message-ID: <20260713155901.GB656327@shredder> References: <20260708060537.17188-1-xuanqiang.luo@linux.dev> <20260708060537.17188-3-xuanqiang.luo@linux.dev> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260708060537.17188-3-xuanqiang.luo@linux.dev> X-ClientProxiedBy: FR4P281CA0412.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:d0::20) To SA3PR12MB7901.namprd12.prod.outlook.com (2603:10b6:806:306::12) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SA3PR12MB7901:EE_|CY8PR12MB7585:EE_ X-MS-Office365-Filtering-Correlation-Id: 82041767-6518-4f77-aa67-08dee0f7ad6e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|1800799024|366016|7416014|376014|6133799003|56012099006|4143699003|11063799006|22082099003|18002099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?k57qyPvHFTK/9PLqk9/XxQL/h1JHkRWjxXqeZSaNPH7ntSRZCJfwRpXsjrfh?= =?us-ascii?Q?AF/Qb/CZJvxOG6PwCd/ayVY5uuXdEu+Af/bbD515uG6UMJmf9kh3Sv6wY8zr?= =?us-ascii?Q?B9uqs4rEirDRJ+fdBaHNiCQr6hfcAlqj3F1M0GuViS6sq3D5Zq7sY0jSpy53?= =?us-ascii?Q?aXFp+4af534up5LHesu+3dOIyhzPcBAeP72fzaavSvkGIbp83KnZ/JGdqX/c?= =?us-ascii?Q?C6sNqalvgpnsxxHyWq+PJ+J4734sA5IpHcJ0nDTAlFLTqxYT1abh6VuyxXBT?= =?us-ascii?Q?NVNYC55cvBIn0IYnsVH8XKWXg1NeF9t73TDSconaLU1/iluAeE8xLd0JHjcS?= =?us-ascii?Q?nJWMuOeDa0d/XRoxMz4lciFVLfe55Nynnhs+IohYGzktzDMQkVfonJYNs+Sk?= =?us-ascii?Q?rYxqxXAnzds4sdYPfmrbO/CsJ1fPnj0xdNDL0ZCxHlfZxLWO1gGFf7UoLElJ?= =?us-ascii?Q?W9k7pqZzNWgHH9z+bpbjq7JEBRu2Q3zLei98yYMyqY9MeH0dvuC/YqtpwZNN?= =?us-ascii?Q?twQFQrwZdZNgnLvz+LU2qH8fvd4KO/0KOTvbKO6hgKPq0YY/HhsueuX7pgz4?= =?us-ascii?Q?hxbYt9Wd9doltwRZbQOHniJGSAZnx4EKeCtXUqgCKn9VeA5EMlW77tJPQYXt?= =?us-ascii?Q?9McjSN9l3M71F6r4PXlkIPOsL/JZR7mfXLkEpAZ+wCkjXH+tyBoTqsu/qTCj?= =?us-ascii?Q?QB9nBgGQd0Rnz3GCffzf1IWzbP6CGS7xp4HIBdfOmE7hl65rUdScHkmgf4Lf?= =?us-ascii?Q?vs8CvquE0uG89VHjIPU41XqBGcIA3RbHJxnQv/6/+fpJaHKJABqmDy2+QVEp?= =?us-ascii?Q?z9aSVF97VYilPWx59ONTI32XcgNP0Q7qLzdoH8vampPPxDY3itmPGnYgOVUG?= =?us-ascii?Q?F+/bUpHyBTqW9mB+zzk41KxdzPibo/2UblPm+fkV+Rz9mTZmT8ztJc+V8MP4?= =?us-ascii?Q?gJVxfR/NRugugnBmGEzgmsAv1q9HMm6OqVD28i1ovZ5ngcxVyzTDh/RG5Ugh?= =?us-ascii?Q?n8Z2DU/ERl6KSM/m3/a5B6EDpNMi0GwxD8ZC1MDY61r1+b2T0umKElbd50ow?= =?us-ascii?Q?NzmxLuBpR6QfFLpVdR2ofatWONPUbntsaI6JfXWUivCE56P5795RyjPY//8M?= =?us-ascii?Q?BDssKrqchqFE0/RtmENVAU70Uc2cAWeN7x/NevJ6IDfeXCiSBpPi1aMPuhK9?= =?us-ascii?Q?0NsXHq/gy0Vjxxna8zEkYVYjchWmeBlifuE+YqE/6iAaoBYjdomqcEu6wndj?= =?us-ascii?Q?Sm2I9jSojMgXcT3sgUgGVYHib1bGLh9q0yPbM1ijB4MaDgRGhRffd58o3BZa?= =?us-ascii?Q?q9Qy7iRzsQoEr1hJYCqlIMoZ4wi7T0BKcfxejLc6XbKbkCRwHOe7zgd5/iLb?= =?us-ascii?Q?+Oncu5vKpYBG/PmfmtBZH3Q7Qyr8G5tGT6dLkA6uxlteok1eW6YmAUGdGsJb?= =?us-ascii?Q?zeBej0Zj1hibeFX4ehpILawvQsEB4zFU5ikU1wNYJH30g0+wjOwdaMBVeFir?= =?us-ascii?Q?EyY/Xdvt5zlRwnRiLhEVcKAFHoMprs+WLsFU39HeSzsPGosEOzH3jOygpiVp?= =?us-ascii?Q?Dk3W2qgrgRXKRoqPEOcMGAzHRxCVT+qdHgkcmtlzQC0WJfYUW3s0/E6gH9Zb?= =?us-ascii?Q?e3wKrF/I85fJ4szaypRcSkJyYpPttEzMwMf9atEtcksJvfDvKYFM2TbUChf3?= =?us-ascii?Q?GBP8LenQioCMEoIkB1qGgylb85t8i9mwL2D+pulv470P/bpK?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 82041767-6518-4f77-aa67-08dee0f7ad6e X-MS-Exchange-CrossTenant-AuthSource: SA3PR12MB7901.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Jul 2026 15:59:10.5726 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: d9TZ5h0S5nnNWQcnhbwYjDerfsanCGDxYEDLTJfNe+s7hyR8m7iTk1vkL+MjJirvP4ML9fu/199vzJppER0Iyg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY8PR12MB7585 On Wed, Jul 08, 2026 at 02:05:37PM +0800, xuanqiang.luo@linux.dev wrote: > From: Xuanqiang Luo > > rt_flush_dev() can replace rt->dst.dev with blackhole_netdev while RCU > readers are running. ip_rt_send_redirect() and ip_rt_get_source() both > read rt->dst.dev more than once and use the results in one operation. > > If rt->dst.dev changes between those reads, the operation can use values > from two devices. For example, ip_rt_send_redirect() can use in_dev from > the old device and the L3 master ifindex from blackhole_netdev. > > Read rt->dst.dev once in these two functions and use the snapshot for the > later device accesses. > > Signed-off-by: Xuanqiang Luo Reviewed-by: Ido Schimmel