netdev - Re: [PATCH bpf-next v2 02/16] xsk: Add getsockopt XDP

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Message-ID: <CAJ+HfNid2hFN6ECetptT+pRQhvPpbdm39zQT9O9xVthadeqQWg@mail.gmail.com>
Date:   Sat, 4 May 2019 19:25:50 +0200
From:   Björn Töpel <bjorn.topel@...il.com>
To:     Maxim Mikityanskiy <maximmi@...lanox.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Björn Töpel <bjorn.topel@...el.com>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Jonathan Lemon <bsd@...com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Maciej Fijalkowski <maciejromanfijalkowski@...il.com>
Subject: Re: [PATCH bpf-next v2 02/16] xsk: Add getsockopt XDP_OPTIONS

On Tue, 30 Apr 2019 at 20:12, Maxim Mikityanskiy <maximmi@...lanox.com> wrote:
>
> Make it possible for the application to determine whether the AF_XDP
> socket is running in zero-copy mode. To achieve this, add a new
> getsockopt option XDP_OPTIONS that returns flags. The only flag
> supported for now is the zero-copy mode indicator.
>
> Signed-off-by: Maxim Mikityanskiy <maximmi@...lanox.com>
> Reviewed-by: Tariq Toukan <tariqt@...lanox.com>
> Acked-by: Saeed Mahameed <saeedm@...lanox.com>
> ---
>  include/uapi/linux/if_xdp.h       |  7 +++++++
>  net/xdp/xsk.c                     | 22 ++++++++++++++++++++++
>  tools/include/uapi/linux/if_xdp.h |  7 +++++++
>  3 files changed, 36 insertions(+)
>
> diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h
> index caed8b1614ff..9ae4b4e08b68 100644
> --- a/include/uapi/linux/if_xdp.h
> +++ b/include/uapi/linux/if_xdp.h
> @@ -46,6 +46,7 @@ struct xdp_mmap_offsets {
>  #define XDP_UMEM_FILL_RING             5
>  #define XDP_UMEM_COMPLETION_RING       6
>  #define XDP_STATISTICS                 7
> +#define XDP_OPTIONS                    8
>
>  struct xdp_umem_reg {
>         __u64 addr; /* Start of packet data area */
> @@ -60,6 +61,12 @@ struct xdp_statistics {
>         __u64 tx_invalid_descs; /* Dropped due to invalid descriptor */
>  };
>
> +struct xdp_options {
> +       __u32 flags;
> +};
> +
> +#define XDP_OPTIONS_FLAG_ZEROCOPY (1 << 0)

Nit: The other flags doesn't use "FLAG" in its name, but that doesn't
really matter.

> +
>  /* Pgoff for mmaping the rings */
>  #define XDP_PGOFF_RX_RING                        0
>  #define XDP_PGOFF_TX_RING               0x80000000
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index b68a380f50b3..998199109d5c 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -650,6 +650,28 @@ static int xsk_getsockopt(struct socket *sock, int level, int optname,
>
>                 return 0;
>         }
> +       case XDP_OPTIONS:
> +       {
> +               struct xdp_options opts;
> +
> +               if (len < sizeof(opts))
> +                       return -EINVAL;
> +
> +               opts.flags = 0;

Maybe get rid of this, in favor of "opts = {}" if the structure grows?


> +
> +               mutex_lock(&xs->mutex);
> +               if (xs->zc)
> +                       opts.flags |= XDP_OPTIONS_FLAG_ZEROCOPY;
> +               mutex_unlock(&xs->mutex);
> +
> +               len = sizeof(opts);
> +               if (copy_to_user(optval, &opts, len))
> +                       return -EFAULT;
> +               if (put_user(len, optlen))
> +                       return -EFAULT;
> +
> +               return 0;
> +       }
>         default:
>                 break;
>         }
> diff --git a/tools/include/uapi/linux/if_xdp.h b/tools/include/uapi/linux/if_xdp.h
> index caed8b1614ff..9ae4b4e08b68 100644
> --- a/tools/include/uapi/linux/if_xdp.h
> +++ b/tools/include/uapi/linux/if_xdp.h
> @@ -46,6 +46,7 @@ struct xdp_mmap_offsets {
>  #define XDP_UMEM_FILL_RING             5
>  #define XDP_UMEM_COMPLETION_RING       6
>  #define XDP_STATISTICS                 7
> +#define XDP_OPTIONS                    8
>
>  struct xdp_umem_reg {
>         __u64 addr; /* Start of packet data area */
> @@ -60,6 +61,12 @@ struct xdp_statistics {
>         __u64 tx_invalid_descs; /* Dropped due to invalid descriptor */
>  };
>
> +struct xdp_options {
> +       __u32 flags;
> +};
> +
> +#define XDP_OPTIONS_FLAG_ZEROCOPY (1 << 0)
> +
>  /* Pgoff for mmaping the rings */
>  #define XDP_PGOFF_RX_RING                        0
>  #define XDP_PGOFF_TX_RING               0x80000000
> --
> 2.19.1
>