netdev - Re: [PATCH net-next 3/6] xsk: Add getsockopt XDP

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Date:   Fri, 26 Apr 2019 22:25:45 +0200
From:   Björn Töpel <bjorn.topel@...el.com>
To:     Maxim Mikityanskiy <maximmi@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>,
        Magnus Karlsson <magnus.karlsson@...el.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Jonathan Lemon <bsd@...com>,
        Eran Ben Elisha <eranbe@...lanox.com>,
        Tariq Toukan <tariqt@...lanox.com>
Subject: Re: [PATCH net-next 3/6] xsk: Add getsockopt XDP_OPTIONS

On 2019-04-26 13:42, Maxim Mikityanskiy 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.
> 
> Also query XDP_OPTIONS in the xdpsock sample application. The zero-copy
> flag will be used in the following commits.
>

Please break this up into separate patches; xsk and libbpf.


Björn


> Signed-off-by: Maxim Mikityanskiy <maximmi@...lanox.com>
> ---
>   include/uapi/linux/if_xdp.h       |  7 +++++++
>   net/xdp/xsk.c                     | 22 ++++++++++++++++++++++
>   tools/include/uapi/linux/if_xdp.h |  7 +++++++
>   tools/lib/bpf/xsk.c               | 11 +++++++++++
>   4 files changed, 47 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)
> +
>   /* 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 ca764ed9da41..ff8427552e8d 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -652,6 +652,28 @@ 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;
> +
> +		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
> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> index 8d0078b65486..50d7235e3b21 100644
> --- a/tools/lib/bpf/xsk.c
> +++ b/tools/lib/bpf/xsk.c
> @@ -67,6 +67,7 @@ struct xsk_socket {
>   	int xsks_map_fd;
>   	__u32 queue_id;
>   	char ifname[IFNAMSIZ];
> +	bool zc;
>   };
>   
>   struct xsk_nl_info {
> @@ -525,6 +526,7 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
>   {
>   	struct sockaddr_xdp sxdp = {};
>   	struct xdp_mmap_offsets off;
> +	struct xdp_options opts;
>   	struct xsk_socket *xsk;
>   	socklen_t optlen;
>   	void *map;
> @@ -642,6 +644,15 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
>   		goto out_mmap_tx;
>   	}
>   
> +	optlen = sizeof(opts);
> +	err = getsockopt(xsk->fd, SOL_XDP, XDP_OPTIONS, &opts, &optlen);
> +	if (err) {
> +		err = -errno;
> +		goto out_mmap_tx;
> +	}
> +
> +	xsk->zc = opts.flags & XDP_OPTIONS_FLAG_ZEROCOPY;
> +
>   	if (!(xsk->config.libbpf_flags & XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD)) {
>   		err = xsk_setup_xdp_prog(xsk);
>   		if (err)
>