Fix IPv6 netmask format for sysconfig (#1215)

This change converts the IPv6 netmask from the network_data.json[1]
format to the CIDR style, <IPv6_addr>/<prefix>.

Using an IPv6 address like ffff:ffff:ffff:ffff:: does not work with
NetworkManager, nor networkscripts.

NetworkManager will ignore the route, logging:
  ifcfg-rh: ignoring invalid route at \
    "::/:: via fd00:fd00:fd00:2::fffe dev $DEV" \
    (/etc/sysconfig/network-scripts/route6-$DEV:3): \
    Argument for "::/::" is not ADDR/PREFIX format

Similarly if using networkscripts, ip route fail with error:
  Error: inet6 prefix is expected rather than \
    "fd00:fd00:fd00::/ffff:ffff:ffff:ffff::".

Also a bit of refactoring ...

cloudinit.net.sysconfig.Route.to_string:
* Move a couple of lines around to reduce repeated code.
* if "ADDRESS" not in key -> continute, so that the
  code block following it can be de-indented.
cloudinit.net.network_state:
* Refactors the ipv4_mask_to_net_prefix, ipv6_mask_to_net_prefix
  removes mask_to_net_prefix methods. Utilize ipaddress library to
  do some of the heavy lifting.

LP: #1959148

3 files changed, 134 insertions, 6 deletions

diff --git a/tests/unittests/net/test_init.py b/tests/unittests/net/test_init.py
index b245da94..18b3fe59 100644
--- a/tests/unittests/net/test_init.py
+++ b/tests/unittests/net/test_init.py
@@ -629,7 +629,9 @@ class TestEphemeralIPV4Network(CiTestCase):
                 with net.EphemeralIPv4Network(**params):
                     pass
             error = context_manager.exception
-            self.assertIn("Cannot setup network: netmask", str(error))
+            self.assertIn(
+                "Cannot setup network, invalid prefix or netmask: ", str(error)
+            )
             self.assertEqual(0, m_subp.call_count)
 
     def test_ephemeral_ipv4_network_performs_teardown(self, m_subp):
diff --git a/tests/unittests/net/test_network_state.py b/tests/unittests/net/test_network_state.py
index 88da9f94..471d969a 100644
--- a/tests/unittests/net/test_network_state.py
+++ b/tests/unittests/net/test_network_state.py
@@ -1,5 +1,5 @@
 # This file is part of cloud-init. See LICENSE file for license information.
-
+import ipaddress
 from unittest import mock
 
 import pytest
@@ -163,4 +163,60 @@ class TestNetworkStateParseNameservers:
         ] == sorted(config.dns_searchdomains)
 
 
+class TestNetworkStateHelperFunctions(CiTestCase):
+    def test_mask_to_net_prefix_ipv4(self):
+        netmask_value = "255.255.255.0"
+        expected = 24
+        prefix_value = network_state.ipv4_mask_to_net_prefix(netmask_value)
+        assert prefix_value == expected
+
+    def test_mask_to_net_prefix_all_bits_ipv4(self):
+        netmask_value = "255.255.255.255"
+        expected = 32
+        prefix_value = network_state.ipv4_mask_to_net_prefix(netmask_value)
+        assert prefix_value == expected
+
+    def test_mask_to_net_prefix_to_many_bits_ipv4(self):
+        netmask_value = "33"
+        self.assertRaises(
+            ValueError, network_state.ipv4_mask_to_net_prefix, netmask_value
+        )
+
+    def test_mask_to_net_prefix_all_bits_ipv6(self):
+        netmask_value = "ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff"
+        expected = 128
+        prefix_value = network_state.ipv6_mask_to_net_prefix(netmask_value)
+        assert prefix_value == expected
+
+    def test_mask_to_net_prefix_ipv6(self):
+        netmask_value = "ffff:ffff:ffff:ffff::"
+        expected = 64
+        prefix_value = network_state.ipv6_mask_to_net_prefix(netmask_value)
+        assert prefix_value == expected
+
+    def test_mask_to_net_prefix_raises_value_error(self):
+        netmask_value = "ff:ff:ff:ff::"
+        self.assertRaises(
+            ValueError, network_state.ipv6_mask_to_net_prefix, netmask_value
+        )
+
+    def test_mask_to_net_prefix_to_many_bits_ipv6(self):
+        netmask_value = "129"
+        self.assertRaises(
+            ValueError, network_state.ipv6_mask_to_net_prefix, netmask_value
+        )
+
+    def test_mask_to_net_prefix_ipv4_object(self):
+        netmask_value = ipaddress.IPv4Address("255.255.255.255")
+        expected = 32
+        prefix_value = network_state.ipv4_mask_to_net_prefix(netmask_value)
+        assert prefix_value == expected
+
+    def test_mask_to_net_prefix_ipv6_object(self):
+        netmask_value = ipaddress.IPv6Address("ffff:ffff:ffff::")
+        expected = 48
+        prefix_value = network_state.ipv6_mask_to_net_prefix(netmask_value)
+        assert prefix_value == expected
+
+
 # vi: ts=4 expandtab
diff --git a/tests/unittests/test_net.py b/tests/unittests/test_net.py
index 66a47b0f..47e4ba00 100644
--- a/tests/unittests/test_net.py
+++ b/tests/unittests/test_net.py
@@ -2421,10 +2421,10 @@ pre-down route del -net 10.0.0.0/8 gw 11.0.0.1 metric 3 || true
                     routes:
                         - gateway: 2001:67c:1562:1
                           network: 2001:67c:1
-                          netmask: ffff:ffff:0
+                          netmask: "ffff:ffff::"
                         - gateway: 3001:67c:1562:1
                           network: 3001:67c:1
-                          netmask: ffff:ffff:0
+                          netmask: "ffff:ffff::"
                           metric: 10000
             """
         ),
@@ -2712,8 +2712,8 @@ iface bond0 inet6 static
                 """\
         # Created by cloud-init on instance boot automatically, do not edit.
         #
-        2001:67c:1/ffff:ffff:0 via 2001:67c:1562:1  dev bond0
-        3001:67c:1/ffff:ffff:0 via 3001:67c:1562:1 metric 10000 dev bond0
+        2001:67c:1/32 via 2001:67c:1562:1  dev bond0
+        3001:67c:1/32 via 3001:67c:1562:1 metric 10000 dev bond0
             """
             ),
             "route-bond0": textwrap.dedent(
@@ -3729,6 +3729,76 @@ USERCTL=no
             renderer.render_network_state(ns, target=render_dir)
         self.assertEqual([], os.listdir(render_dir))
 
+    def test_invalid_network_mask_ipv6(self):
+        net_json = {
+            "services": [{"type": "dns", "address": "172.19.0.12"}],
+            "networks": [
+                {
+                    "network_id": "public-ipv6",
+                    "type": "ipv6",
+                    "netmask": "",
+                    "link": "tap1a81968a-79",
+                    "routes": [
+                        {
+                            "gateway": "2001:DB8::1",
+                            "netmask": "ff:ff:ff:ff::",
+                            "network": "2001:DB8:1::1",
+                        },
+                    ],
+                    "ip_address": "2001:DB8::10",
+                    "id": "network1",
+                }
+            ],
+            "links": [
+                {
+                    "ethernet_mac_address": "fa:16:3e:ed:9a:59",
+                    "mtu": None,
+                    "type": "bridge",
+                    "id": "tap1a81968a-79",
+                    "vif_id": "1a81968a-797a-400f-8a80-567f997eb93f",
+                },
+            ],
+        }
+        macs = {"fa:16:3e:ed:9a:59": "eth0"}
+        network_cfg = openstack.convert_net_json(net_json, known_macs=macs)
+        with self.assertRaises(ValueError):
+            network_state.parse_net_config_data(network_cfg, skip_broken=False)
+
+    def test_invalid_network_mask_ipv4(self):
+        net_json = {
+            "services": [{"type": "dns", "address": "172.19.0.12"}],
+            "networks": [
+                {
+                    "network_id": "public-ipv4",
+                    "type": "ipv4",
+                    "netmask": "",
+                    "link": "tap1a81968a-79",
+                    "routes": [
+                        {
+                            "gateway": "172.20.0.1",
+                            "netmask": "255.234.255.0",
+                            "network": "172.19.0.0",
+                        },
+                    ],
+                    "ip_address": "172.20.0.10",
+                    "id": "network1",
+                }
+            ],
+            "links": [
+                {
+                    "ethernet_mac_address": "fa:16:3e:ed:9a:59",
+                    "mtu": None,
+                    "type": "bridge",
+                    "id": "tap1a81968a-79",
+                    "vif_id": "1a81968a-797a-400f-8a80-567f997eb93f",
+                },
+            ],
+        }
+        macs = {"fa:16:3e:ed:9a:59": "eth0"}
+        network_cfg = openstack.convert_net_json(net_json, known_macs=macs)
+        with self.assertRaises(ValueError):
+            network_state.parse_net_config_data(network_cfg, skip_broken=False)
+
     def test_openstack_rendering_samples(self):
         for os_sample in OS_SAMPLES:
             render_dir = self.tmp_dir()