[PATCH 1/1][SRU][B] net: hns3: pad the short frame before sending to the hardware

[Taihsiang Ho (tai271828)]

From: Yunsheng Lin <linyunsheng at huawei.com>

BugLink: http://bugs.launchpad.net/bugs/1860320

The hardware can not handle short frames below or equal to 32
bytes according to the hardware user manual, and it will trigger
a RAS error when the frame's length is below 33 bytes.

This patch pads the SKB when skb->len is below 33 bytes before
sending it to hardware.

Fixes: 76ad4f0ee747 ("net: hns3: Add support of HNS3 Ethernet Driver for hip08 SoC")
Signed-off-by: Yunsheng Lin <linyunsheng at huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong at huawei.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(backported from commit 36c67349a1a1c88b9cf11d7ca7762ababdb38867)
Signed-off-by: Taihsiang Ho (tai271828) <taihsiang.ho at canonical.com>
---
 drivers/net/ethernet/hisilicon/hns3/hns3_enet.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
index a6b834c6d323..c699d3d47633 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
@@ -32,6 +32,18 @@ static const char hns3_driver_string[] =
 static const char hns3_copyright[] = "Copyright (c) 2017 Huawei Corporation.";
 static struct hnae3_client client;
 
+static int debug = -1;
+module_param(debug, int, 0);
+MODULE_PARM_DESC(debug, " Network interface message level setting");
+
+#define DEFAULT_MSG_LEVEL (NETIF_MSG_PROBE | NETIF_MSG_LINK | \
+			   NETIF_MSG_IFDOWN | NETIF_MSG_IFUP)
+
+#define HNS3_INNER_VLAN_TAG	1
+#define HNS3_OUTER_VLAN_TAG	2
+
+#define HNS3_MIN_TX_LEN		33U
+
 /* hns3_pci_tbl - PCI Device ID Table
  *
  * Last entry must be all 0s
@@ -1224,6 +1236,10 @@ netdev_tx_t hns3_nic_net_xmit(struct sk_buff *skb, struct net_device *netdev)
 	int ret;
 	int i;
 
+	/* Hardware can only handle short frames above 32 bytes */
+	if (skb_put_padto(skb, HNS3_MIN_TX_LEN))
+		return NETDEV_TX_OK;
+
 	/* Prefetch the data used later */
 	prefetch(skb->data);
 
-- 
2.17.1