netdev - Re: [PATCH bpf-next 1/2] libbpf: separate XDP program load with xsk socket creation

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Date:   Wed, 4 Nov 2020 13:07:24 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     mariusz.dudek@...il.com
Cc:     Magnus Karlsson <magnus.karlsson@...el.com>,
        Björn Töpel <bjorn.topel@...el.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Networking <netdev@...r.kernel.org>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        bpf <bpf@...r.kernel.org>,
        Mariusz Dudek <mariuszx.dudek@...el.com>
Subject: Re: [PATCH bpf-next 1/2] libbpf: separate XDP program load with xsk
 socket creation

On Wed, Nov 4, 2020 at 1:47 AM <mariusz.dudek@...il.com> wrote:
>
> From: Mariusz Dudek <mariuszx.dudek@...el.com>
>
>         Add support for separation of eBPF program load and xsk socket
>         creation.
>
>         This is needed for use-case when you want to privide as little
>         privileges as possible to the data plane application that will
>         handle xsk socket creation and incoming traffic.
>
>         With this patch the data entity container can be run with only
>         CAP_NET_RAW capability to fulfill its purpose of creating xsk
>         socket and handling packages. In case your umem is larger or
>         equal process limit for MEMLOCK you need either increase the
>         limit or CAP_IPC_LOCK capability.
>
>         To resolve privileges issue two APIs are introduced:
>
>         - xsk_setup_xdp_prog - prepares bpf program if given and
>         loads it on a selected network interface or loads the built in
>         XDP program, if no XDP program is supplied. It can also return
>         xsks_map_fd which is needed by unprivileged process to update
>         xsks_map with AF_XDP socket "fd"
>
>         - xsk_update_xskmap - inserts an AF_XDP socket into an xskmap
>         for a particular xsk_socket
>

Your commit message seems to be heavily shifted right...


> Signed-off-by: Mariusz Dudek <mariuszx.dudek@...el.com>
> ---
>  tools/lib/bpf/libbpf.map |   2 +
>  tools/lib/bpf/xsk.c      | 157 ++++++++++++++++++++++++++++++++-------
>  tools/lib/bpf/xsk.h      |  13 ++++
>  3 files changed, 146 insertions(+), 26 deletions(-)
>

[...]

> diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h
> index 1069c46364ff..c42b91935d3c 100644
> --- a/tools/lib/bpf/xsk.h
> +++ b/tools/lib/bpf/xsk.h
> @@ -201,6 +201,19 @@ struct xsk_umem_config {
>         __u32 flags;
>  };
>
> +struct bpf_prog_cfg {
> +       struct bpf_insn *prog;
> +       const char *license;
> +       size_t insns_cnt;
> +       int xsks_map_fd;
> +};

This config will have problems with backward/forward compatibility.
Please check how xxx_opts are done and use them for extensible options
structs.


> +
> +LIBBPF_API int xsk_setup_xdp_prog(int ifindex,
> +                                 struct bpf_prog_cfg *cfg,
> +                                 int *xsks_map_fd);
> +LIBBPF_API int xsk_update_xskmap(struct xsk_socket *xsk,
> +                                int xsks_map_fd);

this should be called xsk_socket__update_map? BTW, what's xskmap? Is
that a special BPF map type?

> +
>  /* Flags for the libbpf_flags field. */
>  #define XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD (1 << 0)
>
> --
> 2.20.1
>