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Miller" , Jakub Kicinski , Paolo Abeni , David Ahern , Simon Horman , netdev@vger.kernel.org, eric.dumazet@gmail.com, Taehee Yoo Subject: Re: [PATCH v2 net 3/5] ipv6: mcast: fix delay calculation in igmp6_join_group() Message-ID: <20260830154453.GC2974032@shredder> References: <20260828084531.1826790-1-edumazet@google.com> <20260828084531.1826790-4-edumazet@google.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260828084531.1826790-4-edumazet@google.com> X-ClientProxiedBy: FR3P281CA0053.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:4a::6) To PH0PR12MB7957.namprd12.prod.outlook.com (2603:10b6:510:281::22) 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: PH0PR12MB7957:EE_|IA1PR12MB8223:EE_ X-MS-Office365-Filtering-Correlation-Id: 1dc17838-0acb-4e46-ec21-08df06ada7d4 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|23010399003|366016|56012099006|10067099003|11063799006|4143699003|18002099003|22082099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?CMSfBkrQMUvf/TlW57WgEhR8fmjLrffebBPmXCtm2lMCo08KaoentUBp3BIE?= =?us-ascii?Q?2MetjzVOoUriWdDfP5GLq36DWGk+N4LkYGMmW2Mi0zTnVkP3DdFe1zQGibWu?= =?us-ascii?Q?somuEfC7OqxcHtJebeiit/NCo0Ds2mzt5kcJkVxVfx6ZstrFPwUYFQDRi3NB?= =?us-ascii?Q?yn4MrSw9aYiwZ+3Iwc9YjDxDTUPDsqBVOFOdW5CxXUn45r7k5VHTcQxng/OD?= =?us-ascii?Q?ttk7F9HJizW12u//wS2mcQVqE0NsF9DC+uPJ5ypKsFBeKIhCFxth/E4auyCa?= =?us-ascii?Q?PgaKakKNUGGTOcTrdWnsquF6nIw9GDlGk4I3A6FGFh+XTw/iS2PJue3JLC3k?= =?us-ascii?Q?ScesmOaL6K1wY9GCM+V7RO6UeBhZy6atji6JlnJ+nfIJ+ceQfDIM+Xnm6aOF?= =?us-ascii?Q?OOakUYRpDn33tfAouar/WT4d5bkc6w/2KAVAknE/ritxb/fvrXiGCbcY7QDn?= =?us-ascii?Q?WybXqSYbjCFGwQ46OGUhOXyXw/pmjupPtHgs5vpKi++iCq00R38kavIwOdyR?= =?us-ascii?Q?c++bdmPS2iLt3bxGmSzMNXDaHxmQbb78aIYawIKBtkqa85fIc3GL0qJjPXPE?= =?us-ascii?Q?FQVc/99pADkOeZif1jm2dZKOJyjezjjOHAeviFrzVt7rbJN12LFvn7Buyj89?= =?us-ascii?Q?HzY/4kHfNPxU+3WElUTtAAjKPZetcEnWO5adb5xVNCZmjPR0HS2hK21bcBcN?= =?us-ascii?Q?b7ANPLt2cYwDUlWNqocV3ksDRPOwpUF4Alqw2ubOW2pBpZBz0xY0JPbgnTWU?= =?us-ascii?Q?OlvBWIzu1ZanrNeJR5YsHMlbdkA5yF1NOHnJ4oivRtc0dDgkRTTL0LfGOHWF?= =?us-ascii?Q?1hOy1ohAFz/Dlp09mE7GFjzHGtiltz41vuD7dkAAHj5rNdAhlkD3WDh8tXG2?= =?us-ascii?Q?Z2mPZ0sMyq4ggH+NVqmf8pMnotUHJ+0pmhY0E0aEqFlqFxmlizU7l8iSkmGH?= =?us-ascii?Q?HUO5pfb58yQwBapjJeK6EM3dRadG/NUveHOj58XfpEoUPpxYdYgl56LjXyZE?= =?us-ascii?Q?smwNvL4+OA81aCDXtBTx+rjR+X9z1fY54v1QqRPwvk9Tik1xeNCSm8EnWY2G?= =?us-ascii?Q?HjWmnsDT1yYSXeWGnZaDC9xHe2gyNefs+ROtBhbF9tPxCXMRbEbLOtdzLbPD?= =?us-ascii?Q?WWbP543jklxqQSWI3Y1EjhCmOtEejOIDchflNqW9nW0RP9AFmq4mzuIe3uct?= =?us-ascii?Q?6BNeEmO9gRVgnSMIM1Oy1qsQ0OBYwoNZ/GViwscmH7pIhc5FfwBlXULJ5doc?= =?us-ascii?Q?CpErjVCQvXK1pPeIr2Iahg9GKlQ3QzvFTA6B75MmgY8lk+ACGwChGubaNQ3a?= =?us-ascii?Q?xm5JDc4Hx/rrOMnC2ym/CfD6WwpI45284sIgjGo48WT2FsMwdtE9wmBB2MPy?= =?us-ascii?Q?MWfHr7P8LZKqJKL0TUz892yTm+vrHNQoObcBu5Q+RdYALePE9d5U62zq1Lky?= =?us-ascii?Q?8kiqC1rhg8SsENdVCjQxe7Cun/v5BPjE1q1GoJw3Pqux5zRCQA3rhwqTmlGF?= =?us-ascii?Q?gOfso6lXTSzJw8iTp4bnLLTeuoxy8EMHHHvFV/elEjlSSLoPlsSei1UT5TfY?= =?us-ascii?Q?fA5dy0r8wKRkkI144/GgAMH2DEDaw1zAm4U+MfjHhfag8eqhPg2w6Jfgwg2V?= =?us-ascii?Q?NOS+B7MY5dcEv5/u9KoAwh6v6YQB9EwCP9mDBF3OgC4fjBNzl7SMZjgomL+j?= =?us-ascii?Q?Xb2v9CL4OGdDojAN7gPGxFGdRS3EDMjKSfc1LDbGFDIiUSKo?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 1dc17838-0acb-4e46-ec21-08df06ada7d4 X-MS-Exchange-CrossTenant-AuthSource: PH0PR12MB7957.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Aug 2026 15:45:02.7093 (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: EaOSwwxL36UJNkqGINZnV3DDf949A9hZA6YpOmk0b97tYi+65naC4lAYUH97RTK/8jCDdQj9vxqiyg0LtUQEuA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB8223 On Fri, Aug 28, 2026 at 08:45:29AM +0000, Eric Dumazet wrote: > When joining a multicast group, if a report work is already pending > (e.g. scheduled by a query or a previous join), igmp6_join_group() > cancels the delayed work and recalculates the delay: > > if (cancel_delayed_work(&ma->mca_work)) { > refcount_dec(&ma->mca_refcnt); > delay = ma->mca_work.timer.expires - jiffies; > } > > Unlike igmp6_group_queried(), igmp6_join_group() did not check > if delay >= interval. This leads to two issues: > > 1. If the timer has already expired (timer.expires <= jiffies), the > stale expiry is reused by mod_delayed_work(), causing the second > unsolicited report to fire on the very next tick without a > randomized delay. > 2. If the timer was originally armed by a query with a large > maximum response delay, delay could exceed > unsolicited_report_interval(ma->idev). > > Fix this by initializing delay to unsolicited_report_interval(ma->idev) > and re-randomizing it with get_random_u32_below(interval) when > delay >= interval, mirroring the logic in igmp6_group_queried(). > > Fixes: 2d9a93b4902b ("mld: convert from timer to delayed work") Looks like it was broken from the start: Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Eric Dumazet > Cc: Taehee Yoo Reviewed-by: Ido Schimmel