net: hns3: pad the short tunnel frame before sending to hardware

commit d18e811 upstream.

The hardware cannot handle short tunnel frames below 65 bytes,
and will cause vlan tag missing problem. So pads packet size to
65 bytes for tunnel frames to fix this bug.

Fixes: 3db084d("net: hns3: Fix for vxlan tx checksum bug")
Signed-off-by: Yufeng Mo <moyufeng@huawei.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/ethernet/hisilicon/hns3/hns3_enet.c

@@ -73,6 +73,7 @@ MODULE_PARM_DESC(tx_sgl, "Minimum number of frags when using dma_map_sg() to opt
 #define HNS3_OUTER_VLAN_TAG	2
 
 #define HNS3_MIN_TX_LEN		33U
+#define HNS3_MIN_TUN_PKT_LEN	65U
 
 /* hns3_pci_tbl - PCI Device ID Table
  *
@@ -1425,8 +1426,11 @@ static int hns3_set_l2l3l4(struct sk_buff *skb, u8 ol4_proto,
 			       l4.tcp->doff);
 		break;
 	case IPPROTO_UDP:
-		if (hns3_tunnel_csum_bug(skb))
-			return skb_checksum_help(skb);
+		if (hns3_tunnel_csum_bug(skb)) {
+			int ret = skb_put_padto(skb, HNS3_MIN_TUN_PKT_LEN);
+
+			return ret ? ret : skb_checksum_help(skb);
+		}
 
 		hns3_set_field(*type_cs_vlan_tso, HNS3_TXD_L4CS_B, 1);
 		hns3_set_field(*type_cs_vlan_tso, HNS3_TXD_L4T_S,