Re: [PATCH v1 1/4] bpf: Add netpoll kfuncs for sending UDP packets

[Jakub Kicinski <kuba@kernel.org>]

On Mon, 11 May 2026 08:53:41 +0000 Mahe Tardy wrote:
> Add BPF kfuncs that allow BPF programs to send UDP packets via the
> netpoll infrastructure. This provides a mechanism for BPF programs
> (e.g., LSM hooks) to emit telemetry over UDP without depending on
> the regular networking stack.
> 
> The API consists of four kfuncs:
> 
>   bpf_netpoll_create()   - Allocate and set up a netpoll context
>                            (sleepable, SYSCALL prog type only)
>   bpf_netpoll_acquire()  - Acquire a reference to a netpoll context
>   bpf_netpoll_release()  - Release a reference (cleanup via
>                            queue_rcu_work since netpoll_cleanup sleeps)
>   bpf_netpoll_send_udp() - Send a UDP packet (any context, LSM prog
>                            type only for now)
> 
> The implementation follows the established kfunc lifecycle pattern
> (create/acquire/release with refcounting, kptr map storage, dtor
> registration). The netpoll context is wrapped in a refcounted
> bpf_netpoll struct. Cleanup is deferred via queue_rcu_work() because
> netpoll_cleanup() takes rtnl_lock.

We have enough bug reports as is, let's not merge unusable toys.
For any use of netpoll by BPF:

Nacked-by: Jakub Kicinski <kuba@kernel.org>