Re: [PATCH v1 bpf-next 06/11] bpf: Introduce two attach types for BPF_PROG_TYPE_SK_REUSEPORT.

[Andrii Nakryiko]

On Tue, Dec 1, 2020 at 6:49 AM Kuniyuki Iwashima <kuniyu@xxxxxxxxxxxx> wrote:
>
> This commit adds new bpf_attach_type for BPF_PROG_TYPE_SK_REUSEPORT to
> check if the attached eBPF program is capable of migrating sockets.
>
> When the eBPF program is attached, the kernel runs it for socket migration
> only if the expected_attach_type is BPF_SK_REUSEPORT_SELECT_OR_MIGRATE.
> The kernel will change the behaviour depending on the returned value:
>
>   - SK_PASS with selected_sk, select it as a new listener
>   - SK_PASS with selected_sk NULL, fall back to the random selection
>   - SK_DROP, cancel the migration
>
> Link: https://lore.kernel.org/netdev/20201123003828.xjpjdtk4ygl6tg6h@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
> Suggested-by: Martin KaFai Lau <kafai@xxxxxx>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxxxx>
> ---
>  include/uapi/linux/bpf.h       | 2 ++
>  kernel/bpf/syscall.c           | 8 ++++++++
>  tools/include/uapi/linux/bpf.h | 2 ++
>  3 files changed, 12 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 85278deff439..cfc207ae7782 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -241,6 +241,8 @@ enum bpf_attach_type {
>         BPF_XDP_CPUMAP,
>         BPF_SK_LOOKUP,
>         BPF_XDP,
> +       BPF_SK_REUSEPORT_SELECT,
> +       BPF_SK_REUSEPORT_SELECT_OR_MIGRATE,
>         __MAX_BPF_ATTACH_TYPE
>  };
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index f3fe9f53f93c..a0796a8de5ea 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -2036,6 +2036,14 @@ bpf_prog_load_check_attach(enum bpf_prog_type prog_type,
>                 if (expected_attach_type == BPF_SK_LOOKUP)
>                         return 0;
>                 return -EINVAL;
> +       case BPF_PROG_TYPE_SK_REUSEPORT:
> +               switch (expected_attach_type) {
> +               case BPF_SK_REUSEPORT_SELECT:
> +               case BPF_SK_REUSEPORT_SELECT_OR_MIGRATE:
> +                       return 0;
> +               default:
> +                       return -EINVAL;
> +               }

this is a kernel regression, previously expected_attach_type wasn't
enforced, so user-space could have provided any number without an
error.

>         case BPF_PROG_TYPE_EXT:
>                 if (expected_attach_type)
>                         return -EINVAL;
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 85278deff439..cfc207ae7782 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -241,6 +241,8 @@ enum bpf_attach_type {
>         BPF_XDP_CPUMAP,
>         BPF_SK_LOOKUP,
>         BPF_XDP,
> +       BPF_SK_REUSEPORT_SELECT,
> +       BPF_SK_REUSEPORT_SELECT_OR_MIGRATE,
>         __MAX_BPF_ATTACH_TYPE
>  };
>
> --
> 2.17.2 (Apple Git-113)
>