[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, 12 insertions, 4 deletions

diff --git a/cloudinit/net/ephemeral.py b/cloudinit/net/ephemeral.py
index 1dfd1c42..130afa17 100644
--- a/cloudinit/net/ephemeral.py
+++ b/cloudinit/net/ephemeral.py
@@ -9,9 +9,9 @@ from typing import Any, Dict, List, Optional
 import cloudinit.net as net
 from cloudinit import subp
 from cloudinit.net.dhcp import (
+    IscDhclient,
     NoDHCPLeaseError,
     maybe_perform_dhcp_discovery,
-    parse_static_routes,
 )
 
 LOG = logging.getLogger(__name__)
@@ -305,6 +305,7 @@ class EphemeralIPv6Network:
 class EphemeralDHCPv4:
     def __init__(
         self,
+        distro,
         iface=None,
         connectivity_url_data: Optional[Dict[str, Any]] = None,
         dhcp_log_func=None,
@@ -314,6 +315,7 @@ class EphemeralDHCPv4:
         self.lease = None
         self.dhcp_log_func = dhcp_log_func
         self.connectivity_url_data = connectivity_url_data
+        self.distro = distro
 
     def __enter__(self):
         """Setup sandboxed dhcp context, unless connectivity_url can already be
@@ -351,7 +353,9 @@ class EphemeralDHCPv4:
         """
         if self.lease:
             return self.lease
-        leases = maybe_perform_dhcp_discovery(self.iface, self.dhcp_log_func)
+        leases = maybe_perform_dhcp_discovery(
+            self.distro, self.iface, self.dhcp_log_func
+        )
         if not leases:
             raise NoDHCPLeaseError()
         self.lease = leases[-1]
@@ -378,7 +382,7 @@ class EphemeralDHCPv4:
                 kwargs["prefix_or_mask"], kwargs["ip"]
             )
         if kwargs["static_routes"]:
-            kwargs["static_routes"] = parse_static_routes(
+            kwargs["static_routes"] = IscDhclient.parse_static_routes(
                 kwargs["static_routes"]
             )
         if self.connectivity_url_data:
@@ -412,6 +416,7 @@ class EphemeralIPNetwork:
 
     def __init__(
         self,
+        distro,
         interface,
         ipv6: bool = False,
         ipv4: bool = True,
@@ -421,13 +426,16 @@ class EphemeralIPNetwork:
         self.ipv6 = ipv6
         self.stack = contextlib.ExitStack()
         self.state_msg: str = ""
+        self.distro = distro
 
     def __enter__(self):
         # ipv6 dualstack might succeed when dhcp4 fails
         # therefore catch exception unless only v4 is used
         try:
             if self.ipv4:
-                self.stack.enter_context(EphemeralDHCPv4(self.interface))
+                self.stack.enter_context(
+                    EphemeralDHCPv4(self.distro, self.interface)
+                )
             if self.ipv6:
                 self.stack.enter_context(EphemeralIPv6Network(self.interface))
         # v6 link local might be usable