[net-next PATCH 11/11] net: ravb: Add VLAN checksum support

[Paul Barker <paul@pbarker.dev>]

From: Paul Barker <paul.barker.ct@bp.renesas.com>

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@bp.renesas.com>
---
 drivers/net/ethernet/renesas/ravb.h      |  1 +
 drivers/net/ethernet/renesas/ravb_main.c | 27 +++++++++++++++++++++---
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
index 2cb6c4ef1330..bfa834afc03a 100644
--- a/drivers/net/ethernet/renesas/ravb.h
+++ b/drivers/net/ethernet/renesas/ravb.h
@@ -1056,6 +1056,7 @@ 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 832132d44fb4..eb7499d42a9b 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -2063,11 +2063,30 @@ static void ravb_tx_timeout_work(struct work_struct *work)
 
 static bool ravb_can_tx_csum_gbeth(struct sk_buff *skb)
 {
-	/* TODO: Need to add support for VLAN tag 802.1Q */
-	if (skb_vlan_tag_present(skb))
+	u16 net_protocol = ntohs(skb->protocol);
+
+	/* 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 (skb_vlan_tag_present(skb) &&
+	    (skb->vlan_proto != ETH_P_8021Q || net_protocol == ETH_P_8021Q))
 		return false;
 
-	switch (ntohs(skb->protocol)) {
+	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 (net_protocol) {
 	case ETH_P_IP:
 		switch (ip_hdr(skb)->protocol) {
 		case IPPROTO_TCP:
@@ -2772,6 +2791,7 @@ 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 +2934,7 @@ 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