Added _write_network_fallback function to distros.debian and abstract to

distros base, and apply_fallback_network to distros to call
_write_network_fallback. Note that since _write_network_fallback is only
implemented for debian and ubuntu a check is needed to ensure that it does not
break behaviour for other distros.

Added function to disable .cfg files to util, since it may be useful elsewhere

3 files changed, 31 insertions, 0 deletions

diff --git a/cloudinit/distros/__init__.py b/cloudinit/distros/__init__.py
index 74b484a7..e32ddd57 100644
--- a/cloudinit/distros/__init__.py
+++ b/cloudinit/distros/__init__.py
@@ -78,6 +78,10 @@ class Distro(object):
     def _write_network_config(self, settings):
         raise NotImplementedError()
 
+    @abc.abstractmethod
+    def _write_network_fallback(self):
+        raise NotImplementedError()
+
     def _find_tz_file(self, tz):
         tz_file = os.path.join(self.tz_zone_dir, str(tz))
         if not os.path.isfile(tz_file):
@@ -143,6 +147,14 @@ class Distro(object):
             return self._bring_up_interfaces(dev_names)
         return False
 
+    def apply_fallback_network(self, bring_up=True):
+        # Write it out
+        dev_names = self._write_network_fallback()
+        # Now try to bring them up
+        if bring_up:
+            return self._bring_up_interfaces(dev_names)
+        return False
+
     @abc.abstractmethod
     def apply_locale(self, locale, out_fn=None):
         raise NotImplementedError()
diff --git a/cloudinit/distros/debian.py b/cloudinit/distros/debian.py
index 909d6deb..18d5d124 100644
--- a/cloudinit/distros/debian.py
+++ b/cloudinit/distros/debian.py
@@ -82,6 +82,16 @@ class Distro(distros.Distro):
         net.render_network_state(network_state=ns, target="/")
         return []
 
+    def _write_network_fallback(self):
+        # old fallback configuration is obsolete, disable it
+        util.disable_cfg_file('/etc/network/interfaces.d/eth0.cfg')
+        (ns, link_file, syslink_name) = net.find_fallback_network_device()
+        if link_file is not None:
+            util.write_file(syslink_name, link_file)
+        if ns is not None:
+            net.render_network_stat(network_state=ns, target="/")
+        return []
+
     def _bring_up_interfaces(self, device_names):
         use_all = False
         for d in device_names:
diff --git a/cloudinit/util.py b/cloudinit/util.py
index 20916e53..fa3a6163 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -849,6 +849,15 @@ def read_seeded(base="", ext="", timeout=5, retries=10, file_retries=0):
     return (md, ud)
 
 
+def disable_conf_file(conf):
+    # disable .cfg file by renaming it if it exists
+    if not os.path.exists(conf):
+        return None
+    target_path = os.path.join(conf, '.disabled')
+    rename(conf, target_path)
+    return target_path
+
+
 def read_conf_d(confd):
     # Get reverse sorted list (later trumps newer)
     confs = sorted(os.listdir(confd), reverse=True)