net: hns3: Fix for vxlan tx checksum bug

when skb->encapsulation is 0, skb->ip_summed is CHECKSUM_PARTIAL
and it is udp packet, which has a dest port as the IANA assigned.
the hardware is expected to do the checksum offload, but the
hardware will not do the checksum offload when udp dest port is
4789.

This patch fixes it by doing the checksum in software.

Fixes: 76ad4f0e ("net: hns3: Add support of HNS3 Ethernet Driver for hip08 SoC")
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -655,6 +655,32 @@ static void hns3_set_l2l3l4_len(struct sk_buff *skb, u8 ol4_proto,
 	}
 }
 
+/* when skb->encapsulation is 0, skb->ip_summed is CHECKSUM_PARTIAL
+ * and it is udp packet, which has a dest port as the IANA assigned.
+ * the hardware is expected to do the checksum offload, but the
+ * hardware will not do the checksum offload when udp dest port is
+ * 4789.
+ */
+static bool hns3_tunnel_csum_bug(struct sk_buff *skb)
+{
+#define IANA_VXLAN_PORT	4789
+	union {
+		struct tcphdr *tcp;
+		struct udphdr *udp;
+		struct gre_base_hdr *gre;
+		unsigned char *hdr;
+	} l4;
+
+	l4.hdr = skb_transport_header(skb);
+
+	if (!(!skb->encapsulation && l4.udp->dest == htons(IANA_VXLAN_PORT)))
+		return false;
+
+	skb_checksum_help(skb);
+
+	return true;
+}
+
 static int hns3_set_l3l4_type_csum(struct sk_buff *skb, u8 ol4_proto,
 				   u8 il4_proto, u32 *type_cs_vlan_tso,
 				   u32 *ol_type_vlan_len_msec)
@@ -743,6 +769,9 @@ static int hns3_set_l3l4_type_csum(struct sk_buff *skb, u8 ol4_proto,
 			       HNS3_L4T_TCP);
 		break;
 	case IPPROTO_UDP:
+		if (hns3_tunnel_csum_bug(skb))
+			break;
+
 		hnae_set_field(*type_cs_vlan_tso,
 			       HNS3_TXD_L4T_M,
 			       HNS3_TXD_L4T_S,