1 files changed, 32 insertions, 10 deletions

diff --git a/cloudinit/net/dhcp.py b/cloudinit/net/dhcp.py
index 12cf5097..bdc5799f 100644
--- a/cloudinit/net/dhcp.py
+++ b/cloudinit/net/dhcp.py
@@ -40,34 +40,56 @@ class EphemeralDHCPv4(object):
     def __init__(self, iface=None):
         self.iface = iface
         self._ephipv4 = None
+        self.lease = None
 
     def __enter__(self):
+        """Setup sandboxed dhcp context."""
+        return self.obtain_lease()
+
+    def __exit__(self, excp_type, excp_value, excp_traceback):
+        """Teardown sandboxed dhcp context."""
+        self.clean_network()
+
+    def clean_network(self):
+        """Exit _ephipv4 context to teardown of ip configuration performed."""
+        if self.lease:
+            self.lease = None
+        if not self._ephipv4:
+            return
+        self._ephipv4.__exit__(None, None, None)
+
+    def obtain_lease(self):
+        """Perform dhcp discovery in a sandboxed environment if possible.
+
+        @return: A dict representing dhcp options on the most recent lease
+            obtained from the dhclient discovery if run, otherwise an error
+            is raised.
+
+        @raises: NoDHCPLeaseError if no leases could be obtained.
+        """
+        if self.lease:
+            return self.lease
         try:
             leases = maybe_perform_dhcp_discovery(self.iface)
         except InvalidDHCPLeaseFileError:
             raise NoDHCPLeaseError()
         if not leases:
             raise NoDHCPLeaseError()
-        lease = leases[-1]
+        self.lease = leases[-1]
         LOG.debug("Received dhcp lease on %s for %s/%s",
-                  lease['interface'], lease['fixed-address'],
-                  lease['subnet-mask'])
+                  self.lease['interface'], self.lease['fixed-address'],
+                  self.lease['subnet-mask'])
         nmap = {'interface': 'interface', 'ip': 'fixed-address',
                 'prefix_or_mask': 'subnet-mask',
                 'broadcast': 'broadcast-address',
                 'router': 'routers'}
-        kwargs = dict([(k, lease.get(v)) for k, v in nmap.items()])
+        kwargs = dict([(k, self.lease.get(v)) for k, v in nmap.items()])
         if not kwargs['broadcast']:
             kwargs['broadcast'] = bcip(kwargs['prefix_or_mask'], kwargs['ip'])
         ephipv4 = EphemeralIPv4Network(**kwargs)
         ephipv4.__enter__()
         self._ephipv4 = ephipv4
-        return lease
-
-    def __exit__(self, excp_type, excp_value, excp_traceback):
-        if not self._ephipv4:
-            return
-        self._ephipv4.__exit__(excp_type, excp_value, excp_traceback)
+        return self.lease
 
 
 def maybe_perform_dhcp_discovery(nic=None):