Warn users about IPv6 issues when using Docker < 26.0.0

src/ue4docker/build.py

@@ -86,6 +86,24 @@ def build():
             )
             sys.exit(1)
 
+    # Warn the user if they're using an older version of Docker that can't build or run UE 5.4 images without config changes
+    if (
+        config.containerPlatform == "linux"
+        and DockerUtils.isVersionWithoutIPV6Loopback()
+    ):
+        logger.warning(
+            "\n".join(
+                [
+                    "Warning: detected a Docker version older than 26.0.0.",
+                    "Older versions of Docker cannot build or run images for Unreal Engine 5.4 or",
+                    "newer unless the Docker daemon is explicitly configured to enable IPv6 support.",
+                    "For details, see: https://github.com/adamrehn/ue4-docker/issues/357",
+                    "",
+                ]
+            ),
+            False,
+        )
+
     # Create an auto-deleting temporary directory to hold our build context
     with tempfile.TemporaryDirectory() as tempDir:
         contextOrig = join(os.path.dirname(os.path.abspath(__file__)), "dockerfiles")

src/ue4docker/infrastructure/DockerUtils.py

@@ -1,5 +1,6 @@
 import docker, fnmatch, humanfriendly, itertools, json, logging, os, platform, re
 from docker.models.containers import Container
+from packaging.version import Version
 
 from .FilesystemUtils import FilesystemUtils
 
@@ -32,6 +33,15 @@ def info():
         client = docker.from_env()
         return client.info()
 
+    @staticmethod
+    def isVersionWithoutIPV6Loopback():
+        """
+        Determines if the version of the Docker daemon lacks support for using the
+        IPv6 loopback address [::1] when using its default network configuration
+        """
+        dockerVersion = Version(DockerUtils.version()["Version"])
+        return dockerVersion < Version("26.0.0")
+
     @staticmethod
     def exists(name):
         """