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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?pDYSa31tyrR+hSeb+vK8h1uJz/TxlgWyPklE3Pr9EFDdCYpWs5wNT+VBgDtH?= =?us-ascii?Q?LBasmPEJSjVqbPA4iLkhSN8JxE6U7Ewg6XWbD50/Jb8WXQdBpQ/85PS01vRJ?= =?us-ascii?Q?zwp5TwW6qDhmQh1yGn1GyekrzrkkbW8/g/xMduMnZ/l493UVuZhG1oZq/OK5?= =?us-ascii?Q?9hfIExphHX71R5Allq07kkMZt0N+DoW7mN4F+Pf/9jmDJZE+7cjFXFFUmsHO?= =?us-ascii?Q?NNMuFzRVzrNqVdag/z3k7Bq7ARxe9fvuBM6XKItIME3xnizXU2Udxq1j9PAm?= =?us-ascii?Q?nul9DM0IiRdhMf8018U3bbzhg9Hu7wbwixA5MwF175ANRM+dnLi7WJqFECDv?= =?us-ascii?Q?rlM4QhHVXpEGz2AeJCEv15ZHcD2oNcMVupDzxSMSI7+sauABtS5CWcXyKh0B?= =?us-ascii?Q?CZQKcmCBAWvwAMO8QLiqY/u7QpaD5QrqhOJUgQ6kg72TOTcAf2Wx55lFnxSn?= =?us-ascii?Q?cSasXtk1HCLMPbuVPnlOUjyLMzwlAAxdlQ9xIamzJ7U9Hl0Zt76v8H88Irai?= =?us-ascii?Q?gDBKR3MLMDGpk3bc8Y8odaBenb2gu4yW1Cztjow0E3AN6ba0uJ2TqiBCK3FP?= =?us-ascii?Q?+WaB8Qq0EMCf6tVIadq+//IrFLdkD1YzqtFf0XOoT0v1GTrUNjNC+XVWQTUS?= =?us-ascii?Q?EolFOBeE1OjEYdOMcRIsgD0Ap2NP6Qx/mGEiRdXQhvlRBkryrwMmPrLMEWcG?= =?us-ascii?Q?+Y3VfmBeE4zYt2qJlgCnuYDw1+vjxJJnx49QmZ1QWq0b7KDFo2RulcTOFX9D?= =?us-ascii?Q?opVa7hzdn9O+fHGtTgFNAEglmnAz6+0u86zs+GJIIbNYcygpo0bybPOHKc0b?= =?us-ascii?Q?8BHAaKb+ByOyz6mx0XuGCXJjyw1pqXWqkkl8g3mGHKHCimLkUQgTXtvb5luD?= =?us-ascii?Q?sBtKMBFwOwjhWZlUAGBaDRbWFzQCbjrTrmLDqhgaLJSLcOT2yg9wX9zsz88P?= =?us-ascii?Q?au1k5+18886uyx8/1XOxeq68HYgWtXbMvuXUNRa36oOxaicn5xjDf1wXgQK9?= =?us-ascii?Q?l3SNSOaHXWQ1jqktgLuLVa6Hc5Dn/rOjvn+S0VjyQU9R+WkX6I5ocAIiYnK0?= =?us-ascii?Q?5exq9yK8v4jHPo8Y25oZ25OQobYR+7e8K8VYXPGnx5b9O9GmNxyknen6koaW?= =?us-ascii?Q?oc9Y1n6bGaMC37Gx5hSdVJpL0OIT4EMJ2uLxQCTK7ImTQL9OeYnRbFjTBVSr?= =?us-ascii?Q?rWRuheomR6Yt6vvIi4Wyrw/bmkJbVtcN6P7Bvazhw7MJ5Ds3b01MuTfIRmYG?= =?us-ascii?Q?rxdvYu1RKDfLkXv5hwKasSxKzvhNxgqEIF0GW90FyvPo+rc0wNU9jhVniQCO?= =?us-ascii?Q?HYOPV8lT4xUb3wqepibl3JbhTuhYmtHay8c5zoDs3o9qbFOZWmL/2jbHeXrg?= =?us-ascii?Q?/tx69JFRO+n968fGrbcI1vzZ1EkkduJSoKC5+TPNK5jTLR5Sff3GvXJEy2T4?= =?us-ascii?Q?Kxdb6phs0v7glstWNmTXLDdrVmu3meKznwO5lYkysX4PYhF5oVZvDha5Z99E?= =?us-ascii?Q?Q919/PdljxwY+eyJyuYv1C/n3TbOZR8MxybL5Kbj/QXNdL0mBJBDbJgFf886?= =?us-ascii?Q?BU7Deee8U8sWDk7WCOmC+CHIzxLyatoTXs6VadwWIPVNYoQJyoU0Sy4xF2MH?= =?us-ascii?Q?9iEvpg8x+nRgh4hIowK1OqaB5cN/dYvzEkWAs5G9IlZGgAhKpOtmAoZnpOOF?= =?us-ascii?Q?ffNIovWxg1R2/uFMxnyOwEQ/9yfAGKO2Ryez0SEtiA5FU5jXQWUHkgWM/GyG?= =?us-ascii?Q?7nlRuXFvug=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 90d877ce-cd1a-4000-f6b3-08dec268978e X-MS-Exchange-CrossTenant-AuthSource: SA3PR12MB7901.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Jun 2026 18:39:20.9574 (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: BAj2ttu8/z4SODsNLu9+c1XP4+f1hpjjJnmjmKKExTQcStrNZroF1N1Ln3vWgkw6yj4zLGY+a1dzHQKcgXSxhQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA5PPF3C36BFCB5 On Thu, Jun 04, 2026 at 11:26:08AM +1000, David Gibson wrote: > So, I second Stefano's arguments for the most part, as well as > re-iterating that being broken by this change would require the > intersection of two unlikely conditions (misusing NLM_F_APPEND *and* > expecting the "wrong" order). > > That said, Ido, if you're still not convinced I can do this as an > attribute. It's more hassle, but I can make it work. I appreciate the survey that Stefano and you conducted, but there is still a non-zero chance of causing regressions by suddenly giving NLM_F_APPEND a meaning in RTM_NEWADDR. We already tried the "change-and-see-what-happens" methodology once with this feature and it backfired, so it's going to be quite painful if we miss again. As I see it, we have three options: 1. Use NLM_F_APPEND. Relatively easy change in both the kernel and user space, but at the risk of reintroducing regressions. 2. Add a new attribute (e.g., IFA_INSERT_MODE with DEFAULT/APPEND options). Less risky than #1, at the cost of a bit more code in both the kernel and user space. 3. Do nothing. As I understand it, any production software (as opposed to a test script) that cares about the in-scope order will have to maintain a fallback anyway (e.g., iterating over IPv6 addresses in reverse). Therefore, the changes in #1 and #2 are not strictly necessary, yet they are uAPI that the kernel will have to maintain forever. Given the above, my preference would be #3 -> #2 -> #1. The first two options expose the same capability to user space, so #1 doesn't buy us anything over #2, except a bit less code, but we risk introducing a regression. Between #2 and #3, production software can't drop the fallback even if we implement #2, yet #2 requires us to maintain uAPI forever. I think we should accept that the divergence between IPv4 and IPv6 is not ideal, but at least it's predictable and dependable (Fernando is working on a ksft and documentation). That being said, you can send an RFC for #1 and see what others think since at this point it's unclear who is still following the thread. Thanks