Only accept a address from a peer if it is a valid IP address (#6439)

Signed-off-by: Matthew Whitehead <matthew1001@gmail.com>

ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/discovery/PeerDiscoveryAgent.java

@@ -293,7 +293,9 @@ public abstract class PeerDiscoveryAgent {
             .getPacketData(PingPacketData.class)
             .flatMap(PingPacketData::getFrom)
             .map(Endpoint::getHost)
-            .filter(abc -> !abc.equals("127.0.0.1"))
+            .filter(
+                fromAddr ->
+                    (!fromAddr.equals("127.0.0.1") && InetAddresses.isInetAddress(fromAddr)))
             .stream()
             .peek(
                 h ->