[1/2] DHCP: Refactor dhcp client code (#2122)

Move isc-dhclient code to dhcp.py

In support of the upcoming deprecation of
isc-dhcp-client, this code refactors current
dhcp code into classes in dhcp.py. The
primary user-visible change should be the
addition of the following log:

dhcp.py[DEBUG]: DHCP client selected: dhclient

This code lays groundwork to enable
alternate implementations to live side by
side in the codebase to be selected with
distro-defined priority fallback. Note that
maybe_perform_dhcp_discovery() now selects
which dhcp client to call, and then runs the
corresponding client's dhcp_discovery()
method. Currently only class IscDhclient is
implemented, however a yet-to-be-implemented
class Dhcpcd exists to test fallback behavior
and this will be implemented in part two of
this series.

Part of this refactor includes shifting
dhclient service management from hardcoded
calls to the distro-defined manage_service()
method in the *BSDs. Future work is required
in this area to support multiple clients via
select_dhcp_client().

1 files changed, 2 insertions, 59 deletions

diff --git a/cloudinit/sources/DataSourceCloudStack.py b/cloudinit/sources/DataSourceCloudStack.py
index 3cdfeeca..86124e16 100644
--- a/cloudinit/sources/DataSourceCloudStack.py
+++ b/cloudinit/sources/DataSourceCloudStack.py
@@ -207,53 +207,6 @@ def get_default_gateway():
     return None
 
 
-def get_dhclient_d():
-    # find lease files directory
-    supported_dirs = [
-        "/var/lib/dhclient",
-        "/var/lib/dhcp",
-        "/var/lib/NetworkManager",
-    ]
-    for d in supported_dirs:
-        if os.path.exists(d) and len(os.listdir(d)) > 0:
-            LOG.debug("Using %s lease directory", d)
-            return d
-    return None
-
-
-def get_latest_lease(lease_d=None):
-    # find latest lease file
-    if lease_d is None:
-        lease_d = get_dhclient_d()
-    if not lease_d:
-        return None
-    lease_files = os.listdir(lease_d)
-    latest_mtime = -1
-    latest_file = None
-
-    # lease files are named inconsistently across distros.
-    # We assume that 'dhclient6' indicates ipv6 and ignore it.
-    # ubuntu:
-    #   dhclient.<iface>.leases, dhclient.leases, dhclient6.leases
-    # centos6:
-    #   dhclient-<iface>.leases, dhclient6.leases
-    # centos7: ('--' is not a typo)
-    #   dhclient--<iface>.lease, dhclient6.leases
-    for fname in lease_files:
-        if fname.startswith("dhclient6"):
-            # avoid files that start with dhclient6 assuming dhcpv6.
-            continue
-        if not (fname.endswith(".lease") or fname.endswith(".leases")):
-            continue
-
-        abs_path = os.path.join(lease_d, fname)
-        mtime = os.path.getmtime(abs_path)
-        if mtime > latest_mtime:
-            latest_mtime = mtime
-            latest_file = abs_path
-    return latest_file
-
-
 def get_vr_address():
     # Get the address of the virtual router via dhcp leases
     # If no virtual router is detected, fallback on default gateway.
@@ -277,19 +230,12 @@ def get_vr_address():
         return latest_address
 
     # Try dhcp lease files next...
-    lease_file = get_latest_lease()
+    lease_file = dhcp.IscDhclient.get_latest_lease()
     if not lease_file:
         LOG.debug("No lease file found, using default gateway")
         return get_default_gateway()
 
-    with open(lease_file, "r") as fd:
-        for line in fd:
-            if "dhcp-server-identifier" in line:
-                words = line.strip(" ;\r\n").split(" ")
-                if len(words) > 2:
-                    dhcptok = words[2]
-                    LOG.debug("Found DHCP identifier %s", dhcptok)
-                    latest_address = dhcptok
+    lease_file = dhcp.IscDhclient.parse_dhcp_server_from_lease_file(lease_file)
     if not latest_address:
         # No virtual router found, fallback on default gateway
         LOG.debug("No DHCP found, using default gateway")
@@ -306,6 +252,3 @@ datasources = [
 # Return a list of data sources that match this set of dependencies
 def get_datasource_list(depends):
     return sources.list_from_depends(depends, datasources)
-
-
-# vi: ts=4 expandtab