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Date:   Fri, 26 Apr 2019 11:42:35 +0000
From:   Maxim Mikityanskiy <maximmi@...lanox.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Björn Töpel <bjorn.topel@...el.com>,
        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>,
        Maxim Mikityanskiy <maximmi@...lanox.com>
Subject: [PATCH net-next 3/6] xsk: Add getsockopt XDP_OPTIONS

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.

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)
-- 
2.19.1

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