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

1 files changed, 52 insertions, 59 deletions

diff --git a/cloudinit/net/sysconfig.py b/cloudinit/net/sysconfig.py
index 997907bb..ba85c4f6 100644
--- a/cloudinit/net/sysconfig.py
+++ b/cloudinit/net/sysconfig.py
@@ -10,6 +10,7 @@ from configobj import ConfigObj
 from cloudinit import log as logging
 from cloudinit import subp, util
 from cloudinit.distros.parsers import networkmanager_conf, resolv_conf
+from cloudinit.net import network_state
 
 from . import renderer
 from .network_state import (
@@ -190,69 +191,61 @@ class Route(ConfigMap):
         # (because Route can contain a mix of IPv4 and IPv6)
         reindex = -1
         for key in sorted(self._conf.keys()):
-            if "ADDRESS" in key:
-                index = key.replace("ADDRESS", "")
-                address_value = str(self._conf[key])
-                # only accept combinations:
-                # if proto ipv6 only display ipv6 routes
-                # if proto ipv4 only display ipv4 routes
-                # do not add ipv6 routes if proto is ipv4
-                # do not add ipv4 routes if proto is ipv6
-                # (this array will contain a mix of ipv4 and ipv6)
-                if proto == "ipv4" and not self.is_ipv6_route(address_value):
-                    netmask_value = str(self._conf["NETMASK" + index])
-                    gateway_value = str(self._conf["GATEWAY" + index])
-                    # increase IPv4 index
-                    reindex = reindex + 1
-                    buf.write(
-                        "%s=%s\n"
-                        % (
-                            "ADDRESS" + str(reindex),
-                            _quote_value(address_value),
-                        )
-                    )
-                    buf.write(
-                        "%s=%s\n"
-                        % (
-                            "GATEWAY" + str(reindex),
-                            _quote_value(gateway_value),
-                        )
-                    )
+            if "ADDRESS" not in key:
+                continue
+
+            index = key.replace("ADDRESS", "")
+            address_value = str(self._conf[key])
+            netmask_value = str(self._conf["NETMASK" + index])
+            gateway_value = str(self._conf["GATEWAY" + index])
+
+            # only accept combinations:
+            # if proto ipv6 only display ipv6 routes
+            # if proto ipv4 only display ipv4 routes
+            # do not add ipv6 routes if proto is ipv4
+            # do not add ipv4 routes if proto is ipv6
+            # (this array will contain a mix of ipv4 and ipv6)
+            if proto == "ipv4" and not self.is_ipv6_route(address_value):
+                # increase IPv4 index
+                reindex = reindex + 1
+                buf.write(
+                    "%s=%s\n"
+                    % ("ADDRESS" + str(reindex), _quote_value(address_value))
+                )
+                buf.write(
+                    "%s=%s\n"
+                    % ("GATEWAY" + str(reindex), _quote_value(gateway_value))
+                )
+                buf.write(
+                    "%s=%s\n"
+                    % ("NETMASK" + str(reindex), _quote_value(netmask_value))
+                )
+                metric_key = "METRIC" + index
+                if metric_key in self._conf:
+                    metric_value = str(self._conf["METRIC" + index])
                     buf.write(
                         "%s=%s\n"
-                        % (
-                            "NETMASK" + str(reindex),
-                            _quote_value(netmask_value),
-                        )
-                    )
-                    metric_key = "METRIC" + index
-                    if metric_key in self._conf:
-                        metric_value = str(self._conf["METRIC" + index])
-                        buf.write(
-                            "%s=%s\n"
-                            % (
-                                "METRIC" + str(reindex),
-                                _quote_value(metric_value),
-                            )
-                        )
-                elif proto == "ipv6" and self.is_ipv6_route(address_value):
-                    netmask_value = str(self._conf["NETMASK" + index])
-                    gateway_value = str(self._conf["GATEWAY" + index])
-                    metric_value = (
-                        "metric " + str(self._conf["METRIC" + index])
-                        if "METRIC" + index in self._conf
-                        else ""
+                        % ("METRIC" + str(reindex), _quote_value(metric_value))
                     )
-                    buf.write(
-                        "%s/%s via %s %s dev %s\n"
-                        % (
-                            address_value,
-                            netmask_value,
-                            gateway_value,
-                            metric_value,
-                            self._route_name,
-                        )
+            elif proto == "ipv6" and self.is_ipv6_route(address_value):
+                prefix_value = network_state.ipv6_mask_to_net_prefix(
+                    netmask_value
+                )
+                metric_value = (
+                    "metric " + str(self._conf["METRIC" + index])
+                    if "METRIC" + index in self._conf
+                    else ""
+                )
+                buf.write(
+                    "%s/%s via %s %s dev %s\n"
+                    % (
+                        address_value,
+                        prefix_value,
+                        gateway_value,
+                        metric_value,
+                        self._route_name,
                     )
+                )
 
         return buf.getvalue()