[dpdk-stable] [PATCH v2] net/mlx5: fix wrong segmented packet in Rx

[Jiawei Zhu <17826875952@163.com>]

Fixed issue could occur when Mbuf starvation happens
in a middle of reception of a segmented packet.
In such a situation, after release the segments of that
packet, it does not align consumer index to the next stride.
This would cause receive a wrong segmented packet.

Here is a possible error.
- we assume segs_n is 4 and we are receiving 4
  segments multi-segment packet.
- we fail to alloc mbuf when receive the 3th segment
  so it will free the mbufs which packet chain we have
  built. Here are the 1st and 2nd segment.
- Rx queue in this stride, the 1st and the 2nd segment
  are fill the new mbuf and there data will be rand,
  but the 3th and 4th segment are still fill the last data.
  So next if still begin on this stride, it will receive
  wrong multi-segment packet.
- So we should discarded this packets and pass this stride.
  Before exit the loop, we should align the next consumer index.

Fixes: 15a756b63734 ("net/mlx5: fix possible NULL dereference in Rx path")
Cc: stable@dpdk.org

Signed-off-by: Jiawei Zhu <17826875952@163.com>
---
v2:
* Added extra explanation in commit message.
---
 drivers/net/mlx5/mlx5_rxtx.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index 2e4b87c..e3ce9fd 100644
--- a/drivers/net/mlx5/mlx5_rxtx.c
+++ b/drivers/net/mlx5/mlx5_rxtx.c
@@ -1480,6 +1480,9 @@ enum mlx5_txcmp_code {
 				rte_mbuf_raw_free(pkt);
 				pkt = rep;
 			}
+			rq_ci >>= sges_n;
+			++rq_ci;
+			rq_ci <<= sges_n;
 			break;
 		}
 		if (!pkt) {
-- 
1.8.3.1