netdev - Re: [PATCH bpf-next] samples/bpf: fix to xdpsock to avoid recycling frames

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Date:   Mon, 31 Aug 2020 13:11:55 +0200
From:   Björn Töpel <bjorn.topel@...il.com>
To:     Weqaar Janjua <weqaar.a.janjua@...el.com>
Cc:     "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        Björn Töpel <bjorn.topel@...el.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Netdev <netdev@...r.kernel.org>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next] samples/bpf: fix to xdpsock to avoid recycling frames

On Fri, 28 Aug 2020 at 18:18, Weqaar Janjua <weqaar.a.janjua@...el.com> wrote:
>
> The txpush program in the xdpsock sample application is supposed
> to send out all packets in the umem in a round-robin fashion.
> The problem is that it only cycled through the first BATCH_SIZE
> worth of packets. Fixed this so that it cycles through all buffers
> in the umem as intended.
>
> Fixes: 248c7f9c0e21 ("samples/bpf: convert xdpsock to use libbpf for AF_XDP access")
> Signed-off-by: Weqaar Janjua <weqaar.a.janjua@...el.com>

Thanks Weqaar!

Acked-by: Björn Töpel <bjorn.topel@...el.com>

> ---
>  samples/bpf/xdpsock_user.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
> index 19c679456a0e..c821e9867139 100644
> --- a/samples/bpf/xdpsock_user.c
> +++ b/samples/bpf/xdpsock_user.c
> @@ -1004,7 +1004,7 @@ static void rx_drop_all(void)
>         }
>  }
>
> -static void tx_only(struct xsk_socket_info *xsk, u32 frame_nb, int batch_size)
> +static void tx_only(struct xsk_socket_info *xsk, u32 *frame_nb, int batch_size)
>  {
>         u32 idx;
>         unsigned int i;
> @@ -1017,14 +1017,14 @@ static void tx_only(struct xsk_socket_info *xsk, u32 frame_nb, int batch_size)
>         for (i = 0; i < batch_size; i++) {
>                 struct xdp_desc *tx_desc = xsk_ring_prod__tx_desc(&xsk->tx,
>                                                                   idx + i);
> -               tx_desc->addr = (frame_nb + i) << XSK_UMEM__DEFAULT_FRAME_SHIFT;
> +               tx_desc->addr = (*frame_nb + i) << XSK_UMEM__DEFAULT_FRAME_SHIFT;
>                 tx_desc->len = PKT_SIZE;
>         }
>
>         xsk_ring_prod__submit(&xsk->tx, batch_size);
>         xsk->outstanding_tx += batch_size;
> -       frame_nb += batch_size;
> -       frame_nb %= NUM_FRAMES;
> +       *frame_nb += batch_size;
> +       *frame_nb %= NUM_FRAMES;
>         complete_tx_only(xsk, batch_size);
>  }
>
> @@ -1080,7 +1080,7 @@ static void tx_only_all(void)
>                 }
>
>                 for (i = 0; i < num_socks; i++)
> -                       tx_only(xsks[i], frame_nb[i], batch_size);
> +                       tx_only(xsks[i], &frame_nb[i], batch_size);
>
>                 pkt_cnt += batch_size;
>
> --
> 2.20.1
>
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