ixgbe: skip non IPv4 packets in ATR filter

In driver ixgbe, ixgbe_atr may cause crashes for non-ipv4 packets. Just
add a test to check skb->protocol.  It may crash on short packets due
to ip_hdr() access.

Signed-off-by: Guillaume Gaudonville <guillaume.gaudonville@6wind.com>
Acked-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ixgbe/ixgbe_main.c

@@ -6024,7 +6024,6 @@ static void ixgbe_tx_queue(struct ixgbe_adapter *adapter,
 static void ixgbe_atr(struct ixgbe_adapter *adapter, struct sk_buff *skb,
 	              int queue, u32 tx_flags)
 {
-	/* Right now, we support IPv4 only */
 	struct ixgbe_atr_input atr_input;
 	struct tcphdr *th;
 	struct iphdr *iph = ip_hdr(skb);
@@ -6033,6 +6032,9 @@ static void ixgbe_atr(struct ixgbe_adapter *adapter, struct sk_buff *skb,
 	u32 src_ipv4_addr, dst_ipv4_addr;
 	u8 l4type = 0;
 
+	/* Right now, we support IPv4 only */
+	if (skb->protocol != htons(ETH_P_IP))
+		return;
 	/* check if we're UDP or TCP */
 	if (iph->protocol == IPPROTO_TCP) {
 		th = tcp_hdr(skb);