Add ec2 IPv6 IMDS Support (SC-336)

cloudinit/sources/DataSourceEc2.py

@@ -55,7 +55,11 @@ class DataSourceEc2(sources.DataSource):
     # Default metadata urls that will be used if none are provided
     # They will be checked for 'resolveability' and some of the
     # following may be discarded if they do not resolve
-    metadata_urls = ["http://169.254.169.254", "http://instance-data.:8773"]
+    metadata_urls = [
+        "http://169.254.169.254",
+        "http://[fd00:ec2::254]",
+        "http://instance-data.:8773",
+    ]
 
     # The minimum supported metadata_version from the ec2 metadata apis
     min_metadata_version = "2009-04-04"
@@ -253,6 +257,7 @@ def _maybe_fetch_api_token(self, mdurls, timeout=None, max_wait=None):
                 exception_cb=self._imds_exception_cb,
                 request_method=request_method,
                 headers_redact=AWS_TOKEN_REDACT,
+                connect_synchronously=False,
             )
         except uhelp.UrlError:
             # We use the raised exception to interupt the retry loop.