xsk: statistics support

In this commit, a new getsockopt is added: XDP_STATISTICS. This is
used to obtain stats from the sockets.

v2: getsockopt now returns size of stats structure.

Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

include/uapi/linux/if_xdp.h

@@ -38,6 +38,7 @@ struct sockaddr_xdp {
 #define XDP_UMEM_REG			3
 #define XDP_UMEM_FILL_RING		4
 #define XDP_UMEM_COMPLETION_RING	5
+#define XDP_STATISTICS			6
 
 struct xdp_umem_reg {
 	__u64 addr; /* Start of packet data area */
@@ -46,6 +47,12 @@ struct xdp_umem_reg {
 	__u32 frame_headroom; /* Frame head room */
 };
 
+struct xdp_statistics {
+	__u64 rx_dropped; /* Dropped for reasons other than invalid desc */
+	__u64 rx_invalid_descs; /* Dropped due to invalid descriptor */
+	__u64 tx_invalid_descs; /* Dropped due to invalid descriptor */
+};
+
 /* Pgoff for mmaping the rings */
 #define XDP_PGOFF_RX_RING			  0
 #define XDP_PGOFF_TX_RING		 0x80000000

net/xdp/xsk.c

@@ -468,6 +468,49 @@ static int xsk_setsockopt(struct socket *sock, int level, int optname,
 	return -ENOPROTOOPT;
 }
 
+static int xsk_getsockopt(struct socket *sock, int level, int optname,
+			  char __user *optval, int __user *optlen)
+{
+	struct sock *sk = sock->sk;
+	struct xdp_sock *xs = xdp_sk(sk);
+	int len;
+
+	if (level != SOL_XDP)
+		return -ENOPROTOOPT;
+
+	if (get_user(len, optlen))
+		return -EFAULT;
+	if (len < 0)
+		return -EINVAL;
+
+	switch (optname) {
+	case XDP_STATISTICS:
+	{
+		struct xdp_statistics stats;
+
+		if (len < sizeof(stats))
+			return -EINVAL;
+
+		mutex_lock(&xs->mutex);
+		stats.rx_dropped = xs->rx_dropped;
+		stats.rx_invalid_descs = xskq_nb_invalid_descs(xs->rx);
+		stats.tx_invalid_descs = xskq_nb_invalid_descs(xs->tx);
+		mutex_unlock(&xs->mutex);
+
+		if (copy_to_user(optval, &stats, sizeof(stats)))
+			return -EFAULT;
+		if (put_user(sizeof(stats), optlen))
+			return -EFAULT;
+
+		return 0;
+	}
+	default:
+		break;
+	}
+
+	return -EOPNOTSUPP;
+}
+
 static int xsk_mmap(struct file *file, struct socket *sock,
 		    struct vm_area_struct *vma)
 {
@@ -524,7 +567,7 @@ static const struct proto_ops xsk_proto_ops = {
 	.listen =	sock_no_listen,
 	.shutdown =	sock_no_shutdown,
 	.setsockopt =	xsk_setsockopt,
-	.getsockopt =	sock_no_getsockopt,
+	.getsockopt =	xsk_getsockopt,
 	.sendmsg =	xsk_sendmsg,
 	.recvmsg =	sock_no_recvmsg,
 	.mmap =		xsk_mmap,

net/xdp/xsk_queue.h

@@ -36,6 +36,11 @@ struct xsk_queue {
 
 /* Common functions operating for both RXTX and umem queues */
 
+static inline u64 xskq_nb_invalid_descs(struct xsk_queue *q)
+{
+	return q ? q->invalid_descs : 0;
+}
+
 static inline u32 xskq_nb_avail(struct xsk_queue *q, u32 dcnt)
 {
 	u32 entries = q->prod_tail - q->cons_tail;