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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Patrick McHardy , stable@vger.kernel.org, Vega Subject: Re: [PATCH net v2 1/1] ipv4: fib: bound automatic table ID allocation Message-ID: <20260901092135.GA3402711@shredder> References: <7b6bd9bb1bf6bd43db18156f42b2d7f83789a673.1788223735.git.zihanx@nebusec.ai> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7b6bd9bb1bf6bd43db18156f42b2d7f83789a673.1788223735.git.zihanx@nebusec.ai> X-ClientProxiedBy: TLZP290CA0004.ISRP290.PROD.OUTLOOK.COM (2603:1096:950:9::15) To PH0PR12MB7957.namprd12.prod.outlook.com (2603:10b6:510:281::22) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH0PR12MB7957:EE_|DS7PR12MB6335:EE_ X-MS-Office365-Filtering-Correlation-Id: ff4acda5-3100-443d-68dd-08df080a709c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|366016|7416014|376014|1800799024|56012099006|10067099003|4143699003|11063799006|22082099003|18002099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?SEy4LhAQ8TXb/MBhPM0jJU3hrqKSnolk+vx9uUKQm98irxm759ErVTEZRfFS?= =?us-ascii?Q?bVpxC5+mWCuZe7QXlS4QP7siGiH/FkJoYM+ZrANhqZcEOCc8elTKGEqqlJOM?= =?us-ascii?Q?QQEBm/xyQc/L/HtrBvFVP8iq/UFxtLagU9ADg9qpZcqlx1MOtB/klnFzxzXm?= =?us-ascii?Q?zC4L/vzKl/OD7MKS1ve+w3UyVBYc9pzauJAwsu3btiwSzF1duKf9B66s5ejg?= =?us-ascii?Q?QcYSzKlmSnMccXYPCyo2N2G+sFKsBjmaTIKINwe0+d9a3dGNQe18yU+vuLXI?= =?us-ascii?Q?uuLfNZfoRaw++5nrhIA0Gf+BaAf9LJisLBiemynfXHScddVPe2KGNjIdONHs?= =?us-ascii?Q?Td7MF1kxo9r6UpIT5pt84U3QF77QhMG7kE90BJGLj0Onq1x8NsEMYvQS5onA?= =?us-ascii?Q?fOR4zWqF7LggpJGkNar2w2ipyWLT7jQlD6iJWCdu3xOkKTD2DORRgVMZFvGw?= =?us-ascii?Q?5AvuflJx/RgaXEIZ1usmnv8UawaAKPpgnZwYaa14qysLZp5RnDmAxaTQBvlZ?= =?us-ascii?Q?aaWWXR7lfxYLq+HYYP4C3qKNLfQVF3GCp8gvs1u/X1DO9DYui0AM3saSGXhW?= =?us-ascii?Q?jGfIqa8LPtDYVaeaFyRY55isLhHcaAmR/XBreG3OtxOgFhA1+HlQ/eIJ1g/v?= =?us-ascii?Q?EiRRUuy9OgT12u0xjvROvEDjDL6oVJotSLLrLHkSeC8h53VImdJa4eDqUub6?= =?us-ascii?Q?zpUPo01lzJsXGiALQDyCYuxMK3lcJjbqULm3iefz1tJqSUfMU5RLdsm0gY2i?= =?us-ascii?Q?AGx7Cwjs3+mxErlU6FpM8JhMHgsgMXfnbBJzA8BI1HPNnApX1oX/vowbpM2W?= =?us-ascii?Q?7svMrZOksMQ2X6dOlgkOR3PKYFk/iBEnGBtD+Zr3OVp7bXqmWiUMTDtqDg1Y?= =?us-ascii?Q?I7gUa6m7A0ZnKeCkChRKlzbItQBvYNuaw55chnpMHosKJYgqsbLUzGHGn7Ax?= =?us-ascii?Q?30JmrnoZNp3b1fIZRA3HQpyrZIgIN7HMNeFTMtZlzmFUEGi3LQWlfZg4KYal?= =?us-ascii?Q?E6tp6/eNrHTaWRhagkq6MA3EyYFvsMM0f2o15Ywxr+6EgXc8x51scp1gHbOK?= =?us-ascii?Q?mDER1H+IenS9TwuVDIyQ+kTlomRSHQ5Q4wmlBJOQLFv8J/H4elnDpgVuFVaB?= =?us-ascii?Q?X8kaNXrMLc65/cTyHk/vURnl2t/ZwpCXeayK3KKuoubKKoUWMHcRqbvGGF7z?= =?us-ascii?Q?ayCo7Aznqs5ALCblpJEbkj5SfSPqUrzAZM1k8jMRkeHu1pfYcIb0ay1aoY1y?= =?us-ascii?Q?1+QnaCQAVTclyuRYCC6vka/I8AO61e+J0qn5E3NzvoEYO3Gv9z6id8RQ1oU0?= =?us-ascii?Q?RaKOPDoOvCtuerZpf18WjGbDA5bYRYA/1cT8NoeOEHqfF8RqY5KG20evgW68?= =?us-ascii?Q?Ue9bPK2FoS6UcadUO/mPYmpXFm1T+pBc3okwmaKPPJwrVg/qXHg+QtBu3PYt?= =?us-ascii?Q?0nU2C2kN7Q7fdZjxws6pFf8wGtISPZfw4/BdA1AMIJpKoXE5n5PDQAfpVr5N?= =?us-ascii?Q?JwtZiJTMb8727xF/M4tbL106o/Rd0YV0KguYeB7i7nx4fK5BCT1+XdyjA0SW?= =?us-ascii?Q?zGfPMc/+9Ag9zeUZLnCgLE7Oj0L3+gHMhq2sImNnFOafLT93DhRcZ9GynXbW?= =?us-ascii?Q?LsC+zCLoVq+XMBhdMJZtSyuoh8iRlORFJV45FNPRsshZPkCExdRQcrXXOvmj?= =?us-ascii?Q?OM13Rp7WnEDtOSAK8l8XaMjDOatLqhvSnuhvrU1ein+oZewdLXrmg4Lp6ukM?= =?us-ascii?Q?D4f811anVQ=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: ff4acda5-3100-443d-68dd-08df080a709c X-MS-Exchange-CrossTenant-AuthSource: PH0PR12MB7957.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 Sep 2026 09:21:44.3041 (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: DrpJVsw0mOK3M58BLMcfWljaNStcczwNSjU04PY4eT0VwG1DTJSRlzccMBZoKxS0NLRLmJwqvEAC5b1TYrRcyw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR12MB6335 On Tue, Sep 01, 2026 at 03:00:01AM +0000, Zihan Xi wrote: > fib_empty_table() probes every table ID from 1 until it finds a > free one. IPv4 tables are stored in a 256-bucket hash table, so a > dense set of IDs makes each probe walk a growing hash chain while > RTNL is held. > > Automatic table assignment ("ip rule ... table 0") is an IPv4-only > legacy path. Bound the automatically allocated ID to 4096 so the > RTNL hold stays bounded, without changing lookups of explicitly > specified table IDs. > > Fixes: b801f54917b7 ("[NET]: Increate RT_TABLE_MAX to 2^32") > Cc: stable@vger.kernel.org > Reported-by: Vega > Suggested-by: Ido Schimmel > Assisted-by: Codex:gpt-5.4 > Signed-off-by: Zihan Xi Reviewed-by: Ido Schimmel The bots will likely complain about the change in behavior because the commit message doesn't spell it out. I explained why I think it's safe in [1]. In addition, I checked, and both NetworkManager [2] and systemd [3][4] explicitly forbid "table 0". [1] https://lore.kernel.org/all/20260831110647.GA3202627@shredder/ [2] https://github.com/NetworkManager/NetworkManager/blob/2e83a4082b223499c4f1bba156998d0171071967/src/libnm-core-impl/nm-setting-ip-config.c#L2747-L2758 [3] https://github.com/systemd/systemd/blob/9b62fd169e06d14cbab801c66f2f9c2006edb75c/src/network/networkd-route-util.c#L456-L457 [4] https://www.freedesktop.org/software/systemd/man/latest/systemd.network.html#Table=