Re: [PATCH net-net] tun: Assign missing bpf_net_context.

[Sebastian Andrzej Siewior]

On 2024-09-12 17:03:15 [+0200], Daniel Borkmann wrote:
> 
> Oh well, quite annoying that we need this context now everywhere also outside of XDP :(
> Sebastian, do you see any way where this could be noop for !PREEMPT_RT?

This isn't related to XDP but to the redirect part of BPF which is (or
was) using per-CPU variables.
I don't know how much pain it causes here for you and how much of this
is actually helping and not making anything worse:
- If netkit::active is likely to be NULL you could limit assigning the
  context only if it != NULL

- If you can ensure (via verifier) that netkit_run() won't access the
  redirect helper (such as bpf_redirect()) and won't return
  NETKIT_REDIRECT (as a consequence) then the assignment could be
  avoided in this case.

Sebastian