Re: [PATCH bpf-next] selftests/bpf: fix compilation failure when CONFIG_NET_FOU!=y

[Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>]

On Fri, Jul 19, 2024 at 8:45 AM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
>
> Hi Artem,
>
> On 7/18/24 4:31 PM, Artem Savkov wrote:
> > Without CONFIG_NET_FOU bpf selftests are unable to build because of
> > missing definitions. Add ___local versions of struct bpf_fou_encap and
> > enum bpf_fou_encap_type to fix the issue.
> >
> > Signed-off-by: Artem Savkov <asavkov@xxxxxxxxxx>
>
> This breaks BPF CI, ptal:
>
> https://github.com/kernel-patches/bpf/actions/runs/9999691294/job/27641198557
>
>    [...]
>      CLNG-BPF [test_maps] btf__core_reloc_existence___wrong_field_defs.bpf.o
>      CLNG-BPF [test_maps] verifier_bswap.bpf.o
>      CLNG-BPF [test_maps] test_core_reloc_existence.bpf.o
>      CLNG-BPF [test_maps] test_global_func8.bpf.o
>      CLNG-BPF [test_maps] verifier_bitfield_write.bpf.o
>      CLNG-BPF [test_maps] local_storage_bench.bpf.o
>      CLNG-BPF [test_maps] verifier_runtime_jit.bpf.o
>      CLNG-BPF [test_maps] test_pkt_access.bpf.o
>    progs/test_tunnel_kern.c:39:5: error: conflicting types for 'bpf_skb_set_fou_encap'
>       39 | int bpf_skb_set_fou_encap(struct __sk_buff *skb_ctx,
>          |     ^
>    /tmp/work/bpf/bpf/tools/testing/selftests/bpf/tools/include/vmlinux.h:107714:12: note: previous declaration is here
>     107714 | extern int bpf_skb_set_fou_encap(struct __sk_buff *skb_ctx, struct bpf_fou_encap *encap, int type) __weak __ksym;
>            |            ^
>    progs/test_tunnel_kern.c:41:5: error: conflicting types for 'bpf_skb_get_fou_encap'
>       41 | int bpf_skb_get_fou_encap(struct __sk_buff *skb_ctx,
>          |     ^
>    /tmp/work/bpf/bpf/tools/testing/selftests/bpf/tools/include/vmlinux.h:107715:12: note: previous declaration is here
>     107715 | extern int bpf_skb_get_fou_encap(struct __sk_buff *skb_ctx, struct bpf_fou_encap *encap) __weak __ksym;
>            |            ^
>      CLNG-BPF [test_maps] verifier_typedef.bpf.o
>      CLNG-BPF [test_maps] user_ringbuf_fail.bpf.o
>      CLNG-BPF [test_maps] verifier_map_in_map.bpf.o
>    progs/test_tunnel_kern.c:782:35: error: incompatible pointer types passing 'struct bpf_fou_encap___local *' to parameter of type 'struct bpf_fou_encap *' [-Werror,-Wincompatible-pointer-types]
>      782 |         ret = bpf_skb_set_fou_encap(skb, &encap, FOU_BPF_ENCAP_GUE___local);
>          |                                          ^~~~~~
>    /tmp/work/bpf/bpf/tools/testing/selftests/bpf/tools/include/vmlinux.h:107714:83: note: passing argument to parameter 'encap' here
>     107714 | extern int bpf_skb_set_fou_encap(struct __sk_buff *skb_ctx, struct bpf_fou_encap *encap, int type) __weak __ksym;

It's a good idea to introduce struct bpf_fou_encap___local
for !FOU builds, but kfunc signature needs to stay and
__local variable needs to be type casted to (struct bpf_fou_encap *)
when calling kfunc.