[net-next PATCH v2 10/10] net: ravb: Add VLAN checksum support

[Paul Barker <paul.barker.ct@xxxxxxxxxxxxxx>]

The GbEth IP supports offloading checksum calculation for VLAN-tagged
packets, provided that the EtherType is 0x8100 and only one VLAN tag is
present.

Signed-off-by: Paul Barker <paul.barker.ct@xxxxxxxxxxxxxx>
---
 drivers/net/ethernet/renesas/ravb.h      |  1 +
 drivers/net/ethernet/renesas/ravb_main.c | 24 ++++++++++++++++++++----
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
index d7b3810ce21b..7b48060c250b 100644
--- a/drivers/net/ethernet/renesas/ravb.h
+++ b/drivers/net/ethernet/renesas/ravb.h
@@ -1055,6 +1055,7 @@ struct ravb_hw_info {
 	size_t gstrings_size;
 	netdev_features_t net_hw_features;
 	netdev_features_t net_features;
+	netdev_features_t vlan_features;
 	int stats_len;
 	u32 tccr_mask;
 	u32 tx_max_frame_size;
diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 14b4462331b0..bc56f1f4bec9 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -2063,13 +2063,27 @@ static void ravb_tx_timeout_work(struct work_struct *work)
 
 static bool ravb_can_tx_csum_gbeth(struct sk_buff *skb)
 {
+	u16 net_protocol = ntohs(skb->protocol);
 	u8 inner_protocol;
 
-	/* TODO: Need to add support for VLAN tag 802.1Q */
-	if (skb_vlan_tag_present(skb))
-		return false;
+	/* GbEth IP can calculate the checksum if:
+	 * - there are zero or one VLAN headers with TPID=0x8100
+	 * - the network protocol is IPv4 or IPv6
+	 * - the transport protocol is TCP, UDP or ICMP
+	 * - the packet is not fragmented
+	 */
+
+	if (net_protocol == ETH_P_8021Q) {
+		struct vlan_hdr vhdr, *vh;
+
+		vh = skb_header_pointer(skb, ETH_HLEN, sizeof(vhdr), &vhdr);
+		if (!vh)
+			return false;
+
+		net_protocol = ntohs(vh->h_vlan_encapsulated_proto);
+	}
 
-	switch (ntohs(skb->protocol)) {
+	switch (net_protocol) {
 	case ETH_P_IP:
 		inner_protocol = ip_hdr(skb)->protocol;
 		break;
@@ -2772,6 +2786,7 @@ static const struct ravb_hw_info gbeth_hw_info = {
 	.gstrings_size = sizeof(ravb_gstrings_stats_gbeth),
 	.net_hw_features = NETIF_F_RXCSUM | NETIF_F_HW_CSUM,
 	.net_features = NETIF_F_RXCSUM | NETIF_F_HW_CSUM,
+	.vlan_features = NETIF_F_RXCSUM | NETIF_F_HW_CSUM,
 	.stats_len = ARRAY_SIZE(ravb_gstrings_stats_gbeth),
 	.tccr_mask = TCCR_TSRQ0,
 	.tx_max_frame_size = 1522,
@@ -2914,6 +2929,7 @@ static int ravb_probe(struct platform_device *pdev)
 
 	ndev->features = info->net_features;
 	ndev->hw_features = info->net_hw_features;
+	ndev->vlan_features = info->vlan_features;
 
 	error = reset_control_deassert(rstc);
 	if (error)
-- 
2.43.0