[PATCH net-next 5/8] net: hns3: implement ndo_features_check ops for hns3 driver

[Huazhong Tan]

From: Yunsheng Lin <linyunsheng@xxxxxxxxxx>

The function netif_skb_features() will disable the TSO feature
by using dflt_features_check() if the driver does not implement
ndo_features_check ops, which may cause performance degradation
problem when hns3 hardware can do multiple tagged TSO.

Also, the HNS3 hardware only supports checksum on the SKB with
a max header len of 480 bytes, so remove the checksum and TSO
related features when the header len is over 480 bytes.

Signed-off-by: Yunsheng Lin <linyunsheng@xxxxxxxxxx>
Signed-off-by: Huazhong Tan <tanhuazhong@xxxxxxxxxx>
---
 drivers/net/ethernet/hisilicon/hns3/hns3_enet.c | 32 +++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
index 5679a0c..840a1fb 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
@@ -1556,6 +1556,37 @@ static int hns3_nic_set_features(struct net_device *netdev,
 	return 0;
 }
 
+static netdev_features_t hns3_features_check(struct sk_buff *skb,
+					     struct net_device *dev,
+					     netdev_features_t features)
+{
+#define HNS3_MAX_HDR_LEN	480U
+#define HNS3_MAX_L4_HDR_LEN	60U
+
+	size_t len;
+
+	if (skb->ip_summed != CHECKSUM_PARTIAL)
+		return features;
+
+	if (skb->encapsulation)
+		len = skb_inner_transport_header(skb) - skb->data;
+	else
+		len = skb_transport_header(skb) - skb->data;
+
+	/* Assume L4 is 60 byte as TCP is the only protocol with a
+	 * a flexible value, and it's max len is 60 bytes.
+	 */
+	len += HNS3_MAX_L4_HDR_LEN;
+
+	/* Hardware only supports checksum on the skb with a max header
+	 * len of 480 bytes.
+	 */
+	if (len > HNS3_MAX_HDR_LEN)
+		features &= ~(NETIF_F_CSUM_MASK | NETIF_F_GSO_MASK);
+
+	return features;
+}
+
 static void hns3_nic_get_stats64(struct net_device *netdev,
 				 struct rtnl_link_stats64 *stats)
 {
@@ -1970,6 +2001,7 @@ static const struct net_device_ops hns3_nic_netdev_ops = {
 	.ndo_do_ioctl		= hns3_nic_do_ioctl,
 	.ndo_change_mtu		= hns3_nic_change_mtu,
 	.ndo_set_features	= hns3_nic_set_features,
+	.ndo_features_check	= hns3_features_check,
 	.ndo_get_stats64	= hns3_nic_get_stats64,
 	.ndo_setup_tc		= hns3_nic_setup_tc,
 	.ndo_set_rx_mode	= hns3_nic_set_rx_mode,
-- 
2.7.4