fix: skip OS-level port check for addresses outside network namespace

modules/dockerized-services/impl/src/main/java/eu/cloudnetservice/modules/docker/impl/DockerizedLocalCloudServiceFactory.java

@@ -27,6 +27,7 @@
 import eu.cloudnetservice.node.impl.service.InternalCloudServiceManager;
 import eu.cloudnetservice.node.impl.service.defaults.factory.BaseLocalCloudServiceFactory;
 import eu.cloudnetservice.node.impl.tick.DefaultTickLoop;
+import eu.cloudnetservice.node.impl.util.NetworkUtil;
 import eu.cloudnetservice.node.impl.version.ServiceVersionProvider;
 import eu.cloudnetservice.node.service.CloudService;
 import eu.cloudnetservice.node.service.CloudServiceManager;
@@ -95,4 +96,15 @@ public DockerizedLocalCloudServiceFactory(
   public @NonNull String name() {
     return this.dockerConfiguration.factoryName();
   }
+
+  @Override
+  protected boolean isPortInUseAtOsLevel(@NonNull String hostAddress, int port) {
+    // only do OS-level port check if we can actually reach this address
+    // this handles the case where CloudNet runs in a container with an external address configured
+    if (!NetworkUtil.isBindableAddress(hostAddress)) {
+      return false;
+    }
+
+    return super.isPortInUseAtOsLevel(hostAddress, port);
+  }
 }

node/impl/src/main/java/eu/cloudnetservice/node/impl/service/defaults/factory/BaseLocalCloudServiceFactory.java

@@ -119,14 +119,29 @@ protected int findFreeServicePort(
 
   protected boolean isPortInUse(@NonNull CloudServiceManager manager, @NonNull String hostAddress, int port) {
     // check if any local service has the port
+    if (this.isPortUsedByLocalService(manager, hostAddress, port)) {
+      return true;
+    }
+
+    // validate that the port is free at OS level
+    return this.isPortInUseAtOsLevel(hostAddress, port);
+  }
+
+  protected boolean isPortUsedByLocalService(
+    @NonNull CloudServiceManager manager,
+    @NonNull String hostAddress,
+    int port
+  ) {
     for (var cloudService : manager.localCloudServices()) {
       var address = cloudService.serviceInfo().address();
       if (address.host().equals(hostAddress) && address.port() == port) {
         return true;
       }
     }
+    return false;
+  }
 
-    // validate that the port is free
+  protected boolean isPortInUseAtOsLevel(@NonNull String hostAddress, int port) {
     return NetworkUtil.isInUse(hostAddress, port);
   }
 }

node/impl/src/main/java/eu/cloudnetservice/node/impl/util/NetworkUtil.java

@@ -95,6 +95,35 @@ public static boolean checkAssignable(@NonNull HostAndPort hostAndPort) {
     }
   }
 
+  /**
+   * Checks if the given host address is bindable in the current network namespace.
+   */
+  public static boolean isBindableAddress(@NonNull String hostAddress) {
+    // resolve the address to check against available addresses
+    String resolvedAddress;
+    try {
+      // try to parse as IP address first
+      var address = InetAddresses.forString(hostAddress);
+      // wildcard addresses are always bindable
+      if (address.isAnyLocalAddress()) {
+        return true;
+      }
+      resolvedAddress = extractHostAddress(address);
+    } catch (IllegalArgumentException exception) {
+      // not a raw IP address, try to resolve as hostname
+      try {
+        var address = InetAddress.getByName(hostAddress);
+        resolvedAddress = extractHostAddress(address);
+      } catch (UnknownHostException e) {
+        // cannot resolve hostname, not bindable
+        return false;
+      }
+    }
+
+    // check if the resolved address is available on this system
+    return availableIPAddresses().contains(resolvedAddress);
+  }
+
   public static @Nullable HostAndPort parseAssignableHostAndPort(@NonNull String address, boolean withPort) {
     // try to parse host and port from the given string
     var hostAndPort = parseHostAndPort(address, withPort);