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

[Mahe Tardy <mahe.tardy@gmail.com>]

On Mon, May 11, 2026 at 09:40:32AM +0000, bot+bpf-ci@kernel.org wrote:
> > 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 commit message states bpf_netpoll_send_udp() is "LSM prog type only
> for now," but looking at the implementation in bpf_netpoll_kfunc_init(),
> the function registers netpoll_kfunc_set using BPF_PROG_TYPE_UNSPEC:
> 
> net/core/bpf_netpoll.c:bpf_netpoll_kfunc_init() {
>     ...
>     ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_UNSPEC,
>                                            &netpoll_kfunc_set);
>     ...
> }
> 
> Per bpf_prog_type_to_kfunc_hook() in kernel/bpf/btf.c, BPF_PROG_TYPE_UNSPEC
> maps to BTF_KFUNC_HOOK_COMMON, which makes the kfunc available to ALL BPF
> program types, not just LSM.
> 
> The check in btf_kfunc_is_allowed() tests BTF_KFUNC_HOOK_COMMON first and
> returns true if the kfunc is present there, so any program type (tracing,
> kprobe, XDP, sched-cls, etc.) can call bpf_netpoll_send_udp().
> 
> Is the commit message stale, or should the registration be
> BPF_PROG_TYPE_LSM instead of BPF_PROG_TYPE_UNSPEC to match the stated
> design?

Ah indeed, this a stale commit message, will fix in v2. The real
intention is to make it BPF_PROG_TYPE_UNSPEC. Will wait on some more
reviews before submitting.

> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
> 
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/25660780250