netdev - [PATCH bpf-next 2/5] xsk: proper Rx drop statistics update

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Date:   Mon,  4 Jun 2018 13:57:12 +0200
From:   Björn Töpel <bjorn.topel@...il.com>
To:     bjorn.topel@...il.com, magnus.karlsson@...el.com,
        magnus.karlsson@...il.com, alexander.h.duyck@...el.com,
        alexander.duyck@...il.com, ast@...com, brouer@...hat.com,
        daniel@...earbox.net, netdev@...r.kernel.org,
        mykyta.iziumtsev@...aro.org
Cc:     Björn Töpel <bjorn.topel@...el.com>,
        john.fastabend@...il.com, willemdebruijn.kernel@...il.com,
        mst@...hat.com, michael.lundkvist@...csson.com,
        jesse.brandeburg@...el.com, anjali.singhai@...el.com,
        qi.z.zhang@...el.com, francois.ozog@...aro.org,
        ilias.apalodimas@...aro.org, brian.brooks@...aro.org,
        andy@...yhouse.net, michael.chan@...adcom.com
Subject: [PATCH bpf-next 2/5] xsk: proper Rx drop statistics update

From: Björn Töpel <bjorn.topel@...el.com>

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@...el.com>
---
 net/xdp/xsk.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 43554eb56fe6..966307ce4b8e 100644
--- 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;
 }
-- 
2.14.1