Add a function to test whether we have ipv6 support.

lib/chutney/Host.py

@@ -0,0 +1,20 @@
+
+import socket
+import chutney.Util
+
+@chutney.Util.memoized
+def is_ipv6_supported():
+    """Return true iff ipv6 is supported on this host."""
+    try:
+        s = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
+        s.bind(("::1", 0))
+        s.listen(128)
+        a = s.getsockname()
+        s2 = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
+        s2.settimeout(1)
+        s2.connect(a)
+        return True
+    except socket.error:
+        return False
+
+