tg3: Work around HW/FW limitations with vlan encapsulated frames

TG3 appears to have an issue performing TSO and checksum offloading
correclty when the frame has been vlan encapsulated (non-accelrated).
In these cases, tcp checksum is not correctly updated.

This patch attempts to work around this issue.  After the patch,
802.1ad vlans start working correctly over tg3 devices.

CC: Prashant Sreedharan <prashant@broadcom.com>
CC: Michael Chan <mchan@broadcom.com>
Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/tg3.c

@@ -7914,8 +7914,6 @@ static netdev_tx_t tg3_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
 	entry = tnapi->tx_prod;
 	base_flags = 0;
-	if (skb->ip_summed == CHECKSUM_PARTIAL)
-		base_flags |= TXD_FLAG_TCPUDP_CSUM;
 
 	mss = skb_shinfo(skb)->gso_size;
 	if (mss) {
@@ -7929,6 +7927,13 @@ static netdev_tx_t tg3_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
 		hdr_len = skb_transport_offset(skb) + tcp_hdrlen(skb) - ETH_HLEN;
 
+		/* HW/FW can not correctly segment packets that have been
+		 * vlan encapsulated.
+		 */
+		if (skb->protocol == htons(ETH_P_8021Q) ||
+		    skb->protocol == htons(ETH_P_8021AD))
+			return tg3_tso_bug(tp, tnapi, txq, skb);
+
 		if (!skb_is_gso_v6(skb)) {
 			if (unlikely((ETH_HLEN + hdr_len) > 80) &&
 			    tg3_flag(tp, TSO_BUG))
@@ -7979,6 +7984,17 @@ static netdev_tx_t tg3_start_xmit(struct sk_buff *skb, struct net_device *dev)
 				base_flags |= tsflags << 12;
 			}
 		}
+	} else if (skb->ip_summed == CHECKSUM_PARTIAL) {
+		/* HW/FW can not correctly checksum packets that have been
+		 * vlan encapsulated.
+		 */
+		if (skb->protocol == htons(ETH_P_8021Q) ||
+		    skb->protocol == htons(ETH_P_8021AD)) {
+			if (skb_checksum_help(skb))
+				goto drop;
+		} else  {
+			base_flags |= TXD_FLAG_TCPUDP_CSUM;
+		}
 	}
 
 	if (tg3_flag(tp, USE_JUMBO_BDFLAG) &&