On Thu, Jul 30, 2026 at 12:00 PM Reshma Sreekumar <[email protected]> wrote: > > tc_dump_qdisc() walks every netdev in the netns and can span many netlink > batches. RTNL is only held while a single batch is filled, so devices can > be registered or unregistered in between. Since 748bbef5fc6a ("net/sched: > switch tc_dump_qdisc() to for_each_netdev_dump()") the walk resumes on an > ifindex rather than a list position, but ifindexes are reused: a device > created between two batches can be given an ifindex the dump has already > walked past, and is then missed entirely. Before that commit the resume > used a position in the device list, so any unregister shifted every later > device and silently dropped a run of qdiscs from the reply.
I dislike this patch; it will force dump operations to restart on busy netns. Most devices are created with a new ifindex (dev_index_reserve() is called with ifindex == 0) Forcing a given ifindex is rather unusual. I suggest detecting this specific use case instead of slowing down everything.
