ethernet: Add helpers to recognize addresses mapped to IP multicast

IP multicast must sometimes be discriminated from non-IP multicast,
e.g. when determining the forwarding behavior of a given group in the
presence of multicast router ports on an offloaded bridge. Therefore,
provide helpers to identify these groups.
Signed-off-by: Casper Andersson <casper.casan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/etherdevice.h

@@ -428,6 +428,28 @@ static inline bool ether_addr_equal_masked(const u8 *addr1, const u8 *addr2,
 	return true;
 }
 
+static inline bool ether_addr_is_ipv4_mcast(const u8 *addr)
+{
+	u8 base[ETH_ALEN] = { 0x01, 0x00, 0x5e, 0x00, 0x00, 0x00 };
+	u8 mask[ETH_ALEN] = { 0xff, 0xff, 0xff, 0x80, 0x00, 0x00 };
+
+	return ether_addr_equal_masked(addr, base, mask);
+}
+
+static inline bool ether_addr_is_ipv6_mcast(const u8 *addr)
+{
+	u8 base[ETH_ALEN] = { 0x33, 0x33, 0x00, 0x00, 0x00, 0x00 };
+	u8 mask[ETH_ALEN] = { 0xff, 0xff, 0x00, 0x00, 0x00, 0x00 };
+
+	return ether_addr_equal_masked(addr, base, mask);
+}
+
+static inline bool ether_addr_is_ip_mcast(const u8 *addr)
+{
+	return ether_addr_is_ipv4_mcast(addr) ||
+		ether_addr_is_ipv6_mcast(addr);
+}
+
 /**
  * ether_addr_to_u64 - Convert an Ethernet address into a u64 value.
  * @addr: Pointer to a six-byte array containing the Ethernet address