Re: [PATCH bpf] samples/bpf: Fix xdpsock with '-M' parameter missing unload process

[Magnus Karlsson]

On Mon, Jun 28, 2021 at 11:20 AM Wang Hai <wanghai38@xxxxxxxxxx> wrote:
>
> Execute the following command and exit, then execute it again, the
> following error will be reported.
>
> $ sudo ./samples/bpf/xdpsock -i ens4f2 -M
> ^C
> $ sudo ./samples/bpf/xdpsock -i ens4f2 -M
> libbpf: elf: skipping unrecognized data section(16) .eh_frame
> libbpf: elf: skipping relo section(17) .rel.eh_frame for section(16) .eh_frame
> libbpf: Kernel error message: XDP program already attached
> ERROR: link set xdp fd failed
>
> commit c9d27c9e8dc7 ("samples: bpf: Do not unload prog within xdpsock")
> removed the unload prog code because of the presence of bpf_link. This
> is fine if XDP_SHARED_UMEM is disable, but if it is enable, unload prog
> is still needed.

Thank you Wang.

Acked-by: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>

> Fixes: c9d27c9e8dc7 ("samples: bpf: Do not unload prog within xdpsock")
> Signed-off-by: Wang Hai <wanghai38@xxxxxxxxxx>
> ---
>  samples/bpf/xdpsock_user.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
>
> diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
> index 53e300f860bb..33d0bdebbed8 100644
> --- a/samples/bpf/xdpsock_user.c
> +++ b/samples/bpf/xdpsock_user.c
> @@ -96,6 +96,7 @@ static int opt_xsk_frame_size = XSK_UMEM__DEFAULT_FRAME_SIZE;
>  static int opt_timeout = 1000;
>  static bool opt_need_wakeup = true;
>  static u32 opt_num_xsks = 1;
> +static u32 prog_id;
>  static bool opt_busy_poll;
>  static bool opt_reduced_cap;
>
> @@ -461,6 +462,23 @@ static void *poller(void *arg)
>         return NULL;
>  }
>
> +static void remove_xdp_program(void)
> +{
> +       u32 curr_prog_id = 0;
> +
> +       if (bpf_get_link_xdp_id(opt_ifindex, &curr_prog_id, opt_xdp_flags)) {
> +               printf("bpf_get_link_xdp_id failed\n");
> +               exit(EXIT_FAILURE);
> +       }
> +
> +       if (prog_id == curr_prog_id)
> +               bpf_set_link_xdp_fd(opt_ifindex, -1, opt_xdp_flags);
> +       else if (!curr_prog_id)
> +               printf("couldn't find a prog id on a given interface\n");
> +       else
> +               printf("program on interface changed, not removing\n");
> +}
> +
>  static void int_exit(int sig)
>  {
>         benchmark_done = true;
> @@ -471,6 +489,9 @@ static void __exit_with_error(int error, const char *file, const char *func,
>  {
>         fprintf(stderr, "%s:%s:%i: errno: %d/\"%s\"\n", file, func,
>                 line, error, strerror(error));
> +
> +       if (opt_num_xsks > 1)
> +               remove_xdp_program();
>         exit(EXIT_FAILURE);
>  }
>
> @@ -490,6 +511,9 @@ static void xdpsock_cleanup(void)
>                 if (write(sock, &cmd, sizeof(int)) < 0)
>                         exit_with_error(errno);
>         }
> +
> +       if (opt_num_xsks > 1)
> +               remove_xdp_program();
>  }
>
>  static void swap_mac_addresses(void *data)
> @@ -857,6 +881,10 @@ static struct xsk_socket_info *xsk_configure_socket(struct xsk_umem_info *umem,
>         if (ret)
>                 exit_with_error(-ret);
>
> +       ret = bpf_get_link_xdp_id(opt_ifindex, &prog_id, opt_xdp_flags);
> +       if (ret)
> +               exit_with_error(-ret);
> +
>         xsk->app_stats.rx_empty_polls = 0;
>         xsk->app_stats.fill_fail_polls = 0;
>         xsk->app_stats.copy_tx_sendtos = 0;
> --
> 2.17.1
>