[PATCH v2 3/4] net/af_xdp: fix stats reset

[Ciara Loftus <ciara.loftus@intel.com>]

The imissed statistic was not properly reset because it was
read directly from the kernel statistics. To fix this, take note
of the kernel statistic when the stats are reset and deduct this
value from the kernel statistic read during statistics get.

Bugzilla ID: 1430
Fixes: f1debd77efaf ("net/af_xdp: introduce AF_XDP PMD")
cc: stable@dpdk.org

Reported-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Ciara Loftus <ciara.loftus@intel.com>
Acked-by: Maryam Tahhan <mtahhan@redhat.com>
---
v2:
* Removed whitespace in rx_stats struct
* Fixed typo in commit message

 drivers/net/af_xdp/rte_eth_af_xdp.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/net/af_xdp/rte_eth_af_xdp.c b/drivers/net/af_xdp/rte_eth_af_xdp.c
index 9bcf971ae5..193e3576bc 100644
--- a/drivers/net/af_xdp/rte_eth_af_xdp.c
+++ b/drivers/net/af_xdp/rte_eth_af_xdp.c
@@ -124,6 +124,7 @@ struct rx_stats {
 	uint64_t rx_pkts;
 	uint64_t rx_bytes;
 	uint64_t rx_dropped;
+	uint64_t imissed_offset;
 };
 
 struct pkt_rx_queue {
@@ -884,7 +885,8 @@ eth_stats_get(struct rte_eth_dev *dev, struct rte_eth_stats *stats)
 			AF_XDP_LOG(ERR, "getsockopt() failed for XDP_STATISTICS.\n");
 			return -1;
 		}
-		stats->imissed += xdp_stats.rx_dropped;
+		stats->imissed +=
+			(xdp_stats.rx_dropped - internals->rx_queues[i].stats.imissed_offset);
 
 		stats->opackets += stats->q_opackets[i];
 		stats->obytes += stats->q_obytes[i];
@@ -897,13 +899,25 @@ static int
 eth_stats_reset(struct rte_eth_dev *dev)
 {
 	struct pmd_internals *internals = dev->data->dev_private;
-	int i;
+	struct pmd_process_private *process_private = dev->process_private;
+	struct xdp_statistics xdp_stats;
+	socklen_t optlen;
+	int i, ret, fd;
 
 	for (i = 0; i < internals->queue_cnt; i++) {
 		memset(&internals->rx_queues[i].stats, 0,
 					sizeof(struct rx_stats));
 		memset(&internals->tx_queues[i].stats, 0,
 					sizeof(struct tx_stats));
+		fd = process_private->rxq_xsk_fds[i];
+		optlen = sizeof(struct xdp_statistics);
+		ret = fd >= 0 ? getsockopt(fd, SOL_XDP, XDP_STATISTICS,
+					   &xdp_stats, &optlen) : -1;
+		if (ret != 0) {
+			AF_XDP_LOG(ERR, "getsockopt() failed for XDP_STATISTICS.\n");
+			return -1;
+		}
+		internals->rx_queues[i].stats.imissed_offset = xdp_stats.rx_dropped;
 	}
 
 	return 0;
-- 
2.34.1