bonding: Verify RX LACPDU has proper dest mac-addr

The 802.1AX standard states:
"The DA in LACPDUs is the Slow_Protocols_Multicast address."

This patch enforces that and drops LACPDUs with destination MAC
addresses other than Slow_Protocols_Multicast address

Signed-off-by: Mahesh Bandewar <maheshb@google.com>
Reviewed-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_3ad.c

@@ -2485,6 +2485,9 @@ int bond_3ad_lacpdu_recv(const struct sk_buff *skb, struct bonding *bond,
 	if (skb->protocol != PKT_TYPE_LACPDU)
 		return RX_HANDLER_ANOTHER;
 
+	if (!MAC_ADDRESS_EQUAL(eth_hdr(skb)->h_dest, lacpdu_mcast_addr))
+		return RX_HANDLER_ANOTHER;
+
 	lacpdu = skb_header_pointer(skb, 0, sizeof(_lacpdu), &_lacpdu);
 	if (!lacpdu)
 		return RX_HANDLER_ANOTHER;