ixgbe: Add UDP segmentation offload support

Repost from a series by Alexander Duyck to add UDP segmentation offload
support to the igb driver:
https://lore.kernel.org/netdev/20180504003916.4769.66271.stgit@localhost.localdomain/

CC: Alexander Duyck <alexander.h.duyck@intel.com>
CC: Willem de Bruijn <willemb@google.com>
Suggested-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Josh Hunt <johunt@akamai.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbe/ixgbe_main.c

@@ -7946,6 +7946,7 @@ static int ixgbe_tso(struct ixgbe_ring *tx_ring,
 	} ip;
 	union {
 		struct tcphdr *tcp;
+		struct udphdr *udp;
 		unsigned char *hdr;
 	} l4;
 	u32 paylen, l4_offset;
@@ -7969,7 +7970,8 @@ static int ixgbe_tso(struct ixgbe_ring *tx_ring,
 	l4.hdr = skb_checksum_start(skb);
 
 	/* ADV DTYP TUCMD MKRLOC/ISCSIHEDLEN */
-	type_tucmd = IXGBE_ADVTXD_TUCMD_L4T_TCP;
+	type_tucmd = (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4) ?
+		      IXGBE_ADVTXD_TUCMD_L4T_UDP : IXGBE_ADVTXD_TUCMD_L4T_TCP;
 
 	/* initialize outer IP header fields */
 	if (ip.v4->version == 4) {
@@ -7999,12 +8001,20 @@ static int ixgbe_tso(struct ixgbe_ring *tx_ring,
 	/* determine offset of inner transport header */
 	l4_offset = l4.hdr - skb->data;
 
-	/* compute length of segmentation header */
-	*hdr_len = (l4.tcp->doff * 4) + l4_offset;
-
 	/* remove payload length from inner checksum */
 	paylen = skb->len - l4_offset;
-	csum_replace_by_diff(&l4.tcp->check, (__force __wsum)htonl(paylen));
+
+	if (type_tucmd & IXGBE_ADVTXD_TUCMD_L4T_TCP) {
+		/* compute length of segmentation header */
+		*hdr_len = (l4.tcp->doff * 4) + l4_offset;
+		csum_replace_by_diff(&l4.tcp->check,
+				     (__force __wsum)htonl(paylen));
+	} else {
+		/* compute length of segmentation header */
+		*hdr_len = sizeof(*l4.udp) + l4_offset;
+		csum_replace_by_diff(&l4.udp->check,
+				     (__force __wsum)htonl(paylen));
+	}
 
 	/* update gso size and bytecount with header size */
 	first->gso_segs = skb_shinfo(skb)->gso_segs;
@@ -10190,6 +10200,7 @@ ixgbe_features_check(struct sk_buff *skb, struct net_device *dev,
 	if (unlikely(mac_hdr_len > IXGBE_MAX_MAC_HDR_LEN))
 		return features & ~(NETIF_F_HW_CSUM |
 				    NETIF_F_SCTP_CRC |
+				    NETIF_F_GSO_UDP_L4 |
 				    NETIF_F_HW_VLAN_CTAG_TX |
 				    NETIF_F_TSO |
 				    NETIF_F_TSO6);
@@ -10198,6 +10209,7 @@ ixgbe_features_check(struct sk_buff *skb, struct net_device *dev,
 	if (unlikely(network_hdr_len >  IXGBE_MAX_NETWORK_HDR_LEN))
 		return features & ~(NETIF_F_HW_CSUM |
 				    NETIF_F_SCTP_CRC |
+				    NETIF_F_GSO_UDP_L4 |
 				    NETIF_F_TSO |
 				    NETIF_F_TSO6);
 
@@ -10907,7 +10919,7 @@ static int ixgbe_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 			    IXGBE_GSO_PARTIAL_FEATURES;
 
 	if (hw->mac.type >= ixgbe_mac_82599EB)
-		netdev->features |= NETIF_F_SCTP_CRC;
+		netdev->features |= NETIF_F_SCTP_CRC | NETIF_F_GSO_UDP_L4;
 
 #ifdef CONFIG_IXGBE_IPSEC
 #define IXGBE_ESP_FEATURES	(NETIF_F_HW_ESP | \