ixgbe: fix for 82599 errata marking UDP checksum errors

There is an 82599 errata that UDP frames with a zero checksum are
incorrectly marked as checksum invalid by the hardware.  This was
leading to misleading hw_csum_rx_error counts. This patch adds a
test around this counter increase for this condition.
Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ixgbe/ixgbe_main.c

@@ -511,8 +511,11 @@ static void ixgbe_receive_skb(struct ixgbe_q_vector *q_vector,
  * @skb: skb currently being received and modified
  **/
 static inline void ixgbe_rx_checksum(struct ixgbe_adapter *adapter,
-                                     u32 status_err, struct sk_buff *skb)
+				     union ixgbe_adv_rx_desc *rx_desc,
+				     struct sk_buff *skb)
 {
+	u32 status_err = le32_to_cpu(rx_desc->wb.upper.status_error);
+
 	skb->ip_summed = CHECKSUM_NONE;
 
 	/* Rx csum disabled */
@@ -530,6 +533,16 @@ static inline void ixgbe_rx_checksum(struct ixgbe_adapter *adapter,
 		return;
 
 	if (status_err & IXGBE_RXDADV_ERR_TCPE) {
+		u16 pkt_info = rx_desc->wb.lower.lo_dword.hs_rss.pkt_info;
+
+		/*
+		 * 82599 errata, UDP frames with a 0 checksum can be marked as
+		 * checksum errors.
+		 */
+		if ((pkt_info & IXGBE_RXDADV_PKTTYPE_UDP) &&
+		    (adapter->hw.mac.type == ixgbe_mac_82599EB))
+			return;
+
 		adapter->hw_csum_rx_error++;
 		return;
 	}
@@ -803,7 +816,7 @@ static bool ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector,
 			goto next_desc;
 		}
 
-		ixgbe_rx_checksum(adapter, staterr, skb);
+		ixgbe_rx_checksum(adapter, rx_desc, skb);
 
 		/* probably a little skewed due to removing CRC */
 		total_rx_bytes += skb->len;