cloudinit: refactor util.is_ipv4 to net.is_ipv4_address (#292)

This also simplifies the implementation to rely on the stdlib, instead
of our own NIH checking.

4 files changed, 39 insertions, 15 deletions

diff --git a/cloudinit/net/__init__.py b/cloudinit/net/__init__.py
index 08eaf0a3..cb8c1601 100644
--- a/cloudinit/net/__init__.py
+++ b/cloudinit/net/__init__.py
@@ -978,6 +978,22 @@ def is_ip_address(s: str) -> bool:
     return True
 
 
+def is_ipv4_address(s: str) -> bool:
+    """Returns a bool indicating if ``s`` is an IPv4 address.
+
+    :param s:
+        The string to test.
+
+    :return:
+        A bool indicating if the string contains an IPv4 address or not.
+    """
+    try:
+        ipaddress.IPv4Address(s)
+    except ValueError:
+        return False
+    return True
+
+
 class EphemeralIPv4Network(object):
     """Context manager which sets up temporary static network configuration.
 
diff --git a/cloudinit/net/tests/test_init.py b/cloudinit/net/tests/test_init.py
index 909f43c8..32e70b4c 100644
--- a/cloudinit/net/tests/test_init.py
+++ b/cloudinit/net/tests/test_init.py
@@ -1316,4 +1316,26 @@ class TestIsIpAddress:
         expected_call = mock.call(mock.sentinel.ip_address_in)
         assert [expected_call] == m_ip_address.call_args_list
 
+
+class TestIsIpv4Address:
+    """Tests for net.is_ipv4_address.
+
+    Instead of testing with values we rely on the ipaddress stdlib module to
+    handle all values correctly, so simply test that is_ipv4_address defers to
+    the ipaddress module correctly.
+    """
+
+    @pytest.mark.parametrize('ipv4address_mock,expected_return', (
+        (mock.Mock(side_effect=ValueError), False),
+        (mock.Mock(return_value=ipaddress.IPv4Address('192.168.0.1')), True),
+    ))
+    def test_is_ip_address(self, ipv4address_mock, expected_return):
+        with mock.patch('cloudinit.net.ipaddress.IPv4Address',
+                        ipv4address_mock) as m_ipv4address:
+            ret = net.is_ipv4_address(mock.sentinel.ip_address_in)
+        assert expected_return == ret
+        expected_call = mock.call(mock.sentinel.ip_address_in)
+        assert [expected_call] == m_ipv4address.call_args_list
+
+
 # vi: ts=4 expandtab
diff --git a/cloudinit/sources/__init__.py b/cloudinit/sources/__init__.py
index a6e6d202..923e3cea 100644
--- a/cloudinit/sources/__init__.py
+++ b/cloudinit/sources/__init__.py
@@ -602,7 +602,7 @@ class DataSource(metaclass=abc.ABCMeta):
             # if there is an ipv4 address in 'local-hostname', then
             # make up a hostname (LP: #475354) in format ip-xx.xx.xx.xx
             lhost = self.metadata['local-hostname']
-            if util.is_ipv4(lhost):
+            if net.is_ipv4_address(lhost):
                 toks = []
                 if resolve_ip:
                     toks = util.gethostbyaddr(lhost)
diff --git a/cloudinit/util.py b/cloudinit/util.py
index 541a486b..f8e28d2d 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -528,20 +528,6 @@ def multi_log(text, console=True, stderr=True,
             log.log(log_level, text)
 
 
-def is_ipv4(instr):
-    """determine if input string is a ipv4 address. return boolean."""
-    toks = instr.split('.')
-    if len(toks) != 4:
-        return False
-
-    try:
-        toks = [x for x in toks if 0 <= int(x) < 256]
-    except Exception:
-        return False
-
-    return len(toks) == 4
-
-
 @lru_cache()
 def is_BSD():
     return 'BSD' in platform.system()