[PATCH] mlx4_en: add UFO support

[Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>]

Mellanox Ethernet adapters support Large Segmentation Offload for UDP
packets. The only change needed is using the proper header size when the
packet is UDP instead of TCP.

This significantly increases performance for large UDP packets on
platforms which have an expensive dma_map call, like pseries.

On a simple test with 64000 payload size, throughput has increased from
about 6Gbps to 9.5Gbps, while CPU use dropped from about 600% to about
80% or less, on a 8-core Power7 machine.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
---
 drivers/net/ethernet/mellanox/mlx4/en_netdev.c |    2 +-
 drivers/net/ethernet/mellanox/mlx4/en_tx.c     |    7 ++++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
index edd9cb8..59e808a 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
@@ -1660,7 +1660,7 @@ int mlx4_en_init_netdev(struct mlx4_en_dev *mdev, int port,
 	 */
 	dev->hw_features = NETIF_F_SG | NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM;
 	if (mdev->LSO_support)
-		dev->hw_features |= NETIF_F_TSO | NETIF_F_TSO6;
+		dev->hw_features |= NETIF_F_TSO | NETIF_F_TSO6 | NETIF_F_UFO;
 
 	dev->vlan_features = dev->hw_features;
 
diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
index 019d856..2aad5a4 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -39,6 +39,7 @@
 #include <linux/if_vlan.h>
 #include <linux/vmalloc.h>
 #include <linux/tcp.h>
+#include <linux/udp.h>
 #include <linux/moduleparam.h>
 
 #include "mlx4_en.h"
@@ -455,7 +456,11 @@ static int get_real_size(struct sk_buff *skb, struct net_device *dev,
 	int real_size;
 
 	if (skb_is_gso(skb)) {
-		*lso_header_size = skb_transport_offset(skb) + tcp_hdrlen(skb);
+		*lso_header_size = skb_transport_offset(skb);
+		if (skb_shinfo(skb)->gso_type == SKB_GSO_UDP)
+			*lso_header_size += sizeof(struct udphdr);
+		else
+			*lso_header_size += tcp_hdrlen(skb);
 		real_size = CTRL_SIZE + skb_shinfo(skb)->nr_frags * DS_SIZE +
 			ALIGN(*lso_header_size + 4, DS_SIZE);
 		if (unlikely(*lso_header_size != skb_headlen(skb))) {
-- 
1.7.4.4