sfc: Enable accelerated RFS on vlans

As far as I know, the hardware doesn't support matching on both IP
fields and vlan tag, but it can at least match on the IP fields.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

drivers/net/ethernet/sfc/filter.c

@@ -1185,8 +1185,21 @@ int efx_filter_rfs(struct net_device *net_dev, const struct sk_buff *skb,
 
 	nhoff = skb_network_offset(skb);
 
-	if (skb->protocol != htons(ETH_P_IP))
+	if (skb->protocol == htons(ETH_P_8021Q)) {
+		EFX_BUG_ON_PARANOID(skb_headlen(skb) <
+				    nhoff + sizeof(struct vlan_hdr));
+		if (((const struct vlan_hdr *)skb->data + nhoff)->
+		    h_vlan_encapsulated_proto != htons(ETH_P_IP))
+			return -EPROTONOSUPPORT;
+
+		/* This is IP over 802.1q VLAN.  We can't filter on the
+		 * IP 5-tuple and the vlan together, so just strip the
+		 * vlan header and filter on the IP part.
+		 */
+		nhoff += sizeof(struct vlan_hdr);
+	} else if (skb->protocol != htons(ETH_P_IP)) {
 		return -EPROTONOSUPPORT;
+	}
 
 	/* RFS must validate the IP header length before calling us */
 	EFX_BUG_ON_PARANOID(skb_headlen(skb) < nhoff + sizeof(*ip));