net/nm: check for presence of ifcfg files when nm connection files ar…

…e absent (canonical#4645)

On systems that use network manager to manage connections and activate network
interfaces, they may also use ifcfg files for configuring
interfaces using ifcfg-rh network manager plugin. When network manager is used
as the activator, we need to also check for the presence of ifcfg interface
config file when the network manager connection file is absent and if ifcfg-rh
plugin is present.
Hence, with this change, network manager activator first tries to use network
manager connection files to bring up or bring down the interface. If the
connection files are not present and if ifcfg-rh plugin is present, it tries to
use ifcfg files for the interface. If the plugin or the ifcfg files are not
present, the activator fails to activate or deactivate the interface and it
bails out with warning log.

Fixes: canonicalGH-4640

Signed-off-by: Ani Sinha <anisinha@redhat.com>

cloudinit/net/activators.py

@@ -117,6 +117,13 @@ def bring_up_interface(device_name: str) -> bool:
         from cloudinit.net.network_manager import conn_filename
 
         filename = conn_filename(device_name)
+        if filename is None:
+            LOG.warning(
+                "Unable to find an interface config file. "
+                "Unable to bring up interface."
+            )
+            return False
+
         cmd = ["nmcli", "connection", "load", filename]
         if _alter_interface(cmd, device_name):
             cmd = ["nmcli", "connection", "up", "filename", filename]

cloudinit/net/network_manager.py

@@ -17,10 +17,12 @@
 from cloudinit import subp, util
 from cloudinit.net import is_ipv6_address, renderer, subnet_is_ipv6
 from cloudinit.net.network_state import NetworkState
+from cloudinit.net.sysconfig import available_nm_ifcfg_rh
 
 NM_RUN_DIR = "/etc/NetworkManager"
 NM_LIB_DIR = "/usr/lib/NetworkManager"
 NM_CFG_FILE = "/etc/NetworkManager/NetworkManager.conf"
+IFCFG_CFG_FILE = "/etc/sysconfig/network-scripts"
 NM_IPV6_ADDR_GEN_CONF = """# This is generated by cloud-init. Do not edit.
 #
 [.config]
@@ -442,7 +444,7 @@ def render_network_state(
         for con_id, conn in self.connections.items():
             if not conn.valid():
                 continue
-            name = conn_filename(con_id, target)
+            name = nm_conn_filename(con_id, target)
             util.write_file(name, conn.dump(), 0o600)
 
         # Select EUI64 to be used by default by NM for creating the address
@@ -452,12 +454,39 @@ def render_network_state(
         )
 
 
-def conn_filename(con_id, target=None):
+def nm_conn_filename(con_id, target=None):
     target_con_dir = subp.target_path(target, NM_RUN_DIR)
     con_file = f"cloud-init-{con_id}.nmconnection"
     return f"{target_con_dir}/system-connections/{con_file}"
 
 
+def sysconfig_conn_filename(devname, target=None):
+    target_con_dir = subp.target_path(target, IFCFG_CFG_FILE)
+    con_file = f"ifcfg-{devname}"
+    return f"{target_con_dir}/{con_file}"
+
+
+def conn_filename(devname):
+    """
+    This function returns the name of the interface config file.
+    It first checks for presence of network manager connection file.
+    If absent and ifcfg-rh plugin for network manager is available,
+    it returns the name of the ifcfg file if it is present. If the
+    plugin is not present or the plugin is present but ifcfg file is
+    not, it returns None.
+    This function is called from NetworkManagerActivator class in
+    activators.py.
+    """
+    conn_file = nm_conn_filename(devname)
+    # If the network manager connection file is absent, also check for
+    # presence of ifcfg files for the same interface (if nm-ifcfg-rh plugin is
+    # present, network manager can handle ifcfg files). If both network manager
+    # connection file and ifcfg files are absent, return None.
+    if not os.path.isfile(conn_file) and available_nm_ifcfg_rh():
+        conn_file = sysconfig_conn_filename(devname)
+    return conn_file if os.path.isfile(conn_file) else None
+
+
 def cloud_init_nm_conf_filename(target=None):
     target_con_dir = subp.target_path(target, NM_RUN_DIR)
     conf_file = "30-cloud-init-ip6-addr-gen-mode.conf"