On Wed, Feb 10, 2021 at 12:27:38PM -0800, Andrii Nakryiko wrote:
> On Tue, Feb 9, 2021 at 12:11 PM Martin KaFai Lau <kafai@xxxxxx> wrote:
> >
> > This patch adds a "void *owner" member. The existing
> > bpf_tcp_ca test will ensure the bpf_cubic.o and bpf_dctcp.o
> > can be loaded.
> >
> > Signed-off-by: Martin KaFai Lau <kafai@xxxxxx>
> > ---
>
> Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
>
> What will happen if BPF code initializes such non-func ptr member?
> Will libbpf complain or just ignore those values? Ignoring initialized
> members isn't great.
The latter. libbpf will ignore non-func ptr member. The non-func ptr
member stays zero when it is passed to the kernel.
libbpf can be changed to copy this non-func ptr value.
The kernel will decide what to do with it. It will
then be consistent with int/array member like ".name"
and ".flags" where the kernel will verify the value.
I can spin v2 to do that.
>
> > tools/testing/selftests/bpf/bpf_tcp_helpers.h | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/tools/testing/selftests/bpf/bpf_tcp_helpers.h b/tools/testing/selftests/bpf/bpf_tcp_helpers.h
> > index 6a9053162cf2..91f0fac632f4 100644
> > --- a/tools/testing/selftests/bpf/bpf_tcp_helpers.h
> > +++ b/tools/testing/selftests/bpf/bpf_tcp_helpers.h
> > @@ -177,6 +177,7 @@ struct tcp_congestion_ops {
> > * after all the ca_state processing. (optional)
> > */
> > void (*cong_control)(struct sock *sk, const struct rate_sample *rs);
> > + void *owner;
> > };
> >
> > #define min(a, b) ((a) < (b) ? (a) : (b))
> > --
> > 2.24.1
> >
