Improved error message when verifying enode syntax with xdns-enabled (#5346)

* updated error message

Signed-off-by: Nischal Sharma <nischal@web3labs.com>

---------

Signed-off-by: Nischal Sharma <nischal@web3labs.com>
Co-authored-by: Sally MacFarlane <macfarla.github@gmail.com>

besu/src/test/java/org/hyperledger/besu/util/LocalPermissioningConfigurationValidatorTest.java

@@ -212,7 +212,7 @@ public class LocalPermissioningConfigurationValidatorTest {
     Files.write(toml, Resources.toByteArray(configFile));
 
     final ImmutableEnodeDnsConfiguration enodeDnsConfiguration =
-        ImmutableEnodeDnsConfiguration.builder().dnsEnabled(false).updateEnabled(false).build();
+        ImmutableEnodeDnsConfiguration.builder().dnsEnabled(true).updateEnabled(false).build();
 
     assertThatThrownBy(
             () ->
@@ -224,7 +224,6 @@ public class LocalPermissioningConfigurationValidatorTest {
                     toml.toAbsolutePath().toString()))
         .isInstanceOf(IllegalArgumentException.class)
         .hasMessageContaining(
-            "Invalid enode URL syntax 'enode://6f8a80d14311c39f35f516fa664deaaaa13e85b2f7493f37f6144d86991ec012937307647bd3b9a82abe2974e1407241d54947bbb39763a4cac9f77166ad92a0@hostname:4567'. "
-                + "Enode URL should have the following format 'enode://<node_id>@<ip>:<listening_port>[?discport=<discovery_port>]'. Invalid ip address.");
+            "Invalid IP address (or DNS query resolved an invalid IP). --Xdns-enabled is true but --Xdns-update-enabled flag is false.");
   }
 }

ethereum/p2p/src/main/java/org/hyperledger/besu/ethereum/p2p/peers/EnodeURLImpl.java

@@ -80,13 +80,20 @@ public class EnodeURLImpl implements EnodeURL {
       checkStringArgumentNotEmpty(value, "Invalid empty value.");
       return fromURI(URI.create(value), enodeDnsConfiguration);
     } catch (final IllegalArgumentException e) {
-      String message =
+      String message = "";
+      if (enodeDnsConfiguration.dnsEnabled() && !enodeDnsConfiguration.updateEnabled()) {
+        message =
+            "Invalid IP address (or DNS query resolved an invalid IP). --Xdns-enabled is true but --Xdns-update-enabled flag is false.";
+      } else {
+        message =
             String.format(
                 "Invalid enode URL syntax '%s'. Enode URL should have the following format 'enode://<node_id>@<ip>:<listening_port>[?discport=<discovery_port>]'.",
                 value);
         if (e.getMessage() != null) {
           message += " " + e.getMessage();
         }
+      }
+
       throw new IllegalArgumentException(message, e);
     }
   }