xsk: proper Rx drop statistics update

Previously, rx_dropped could be updated incorrectly, e.g. if the XDP
program redirected the frame to a socket bound to a different queue
than where the XDP program was executing.

Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 43554eb..966307c 100644 (file)
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -48,8 +48,10 @@ static int __xsk_rcv(struct xdp_sock *xs, struct xdp_buff *xdp)
        if (xs->dev != xdp->rxq->dev || xs->queue_id != xdp->rxq->queue_index)
                return -EINVAL;
 
-       if (!xskq_peek_id(xs->umem->fq, &id))
+       if (!xskq_peek_id(xs->umem->fq, &id)) {
+               xs->rx_dropped++;
                return -ENOSPC;
+       }
 
        buffer = xdp_umem_get_data_with_headroom(xs->umem, id);
        memcpy(buffer, xdp->data, len);
@@ -57,6 +59,8 @@ static int __xsk_rcv(struct xdp_sock *xs, struct xdp_buff *xdp)
                                      xs->umem->frame_headroom);
        if (!err)
                xskq_discard_id(xs->umem->fq);
+       else
+               xs->rx_dropped++;
 
        return err;
 }
@@ -68,8 +72,6 @@ int xsk_rcv(struct xdp_sock *xs, struct xdp_buff *xdp)
        err = __xsk_rcv(xs, xdp);
        if (likely(!err))
                xdp_return_buff(xdp);
-       else
-               xs->rx_dropped++;
 
        return err;
 }
@@ -87,8 +89,6 @@ int xsk_generic_rcv(struct xdp_sock *xs, struct xdp_buff *xdp)
        err = __xsk_rcv(xs, xdp);
        if (!err)
                xsk_flush(xs);
-       else
-               xs->rx_dropped++;
 
        return err;
 }