wwan: T8412: Fix commit failure when modem is absent or not connected

`mmcli --simple-disconnect` can be called when the modem bearer is not active.
This causes cmd() to raise a `PermissionError` and abort the commit.
Handle the case gracefully so the configuration can be committed before the modem
is physically present or fully connected.

3 files changed, 16 insertions, 2 deletions

diff --git a/python/vyos/ifconfig/wwan.py b/python/vyos/ifconfig/wwan.py
index 2b5714b85..ffd3d0a67 100644
--- a/python/vyos/ifconfig/wwan.py
+++ b/python/vyos/ifconfig/wwan.py
@@ -26,6 +26,10 @@ class WWANIf(Interface):
         },
     }
 
+    def _create(self):
+        # we can not create this interface as it is managed by the Kernel
+        pass
+
     def remove(self):
         """
         Remove interface from config. Removing the interface deconfigures all
diff --git a/python/vyos/utils/network.py b/python/vyos/utils/network.py
index f20450a5f..8985224f3 100644
--- a/python/vyos/utils/network.py
+++ b/python/vyos/utils/network.py
@@ -238,7 +238,11 @@ def is_wwan_connected(interface):
 
     modem = interface.lstrip('wwan')
 
-    tmp = cmd(f'mmcli --modem {modem} --output-json')
+    try:
+        tmp = cmd(f'mmcli --modem {modem} --output-json')
+    except OSError:
+        return False
+
     tmp = loads(tmp)
 
     # return True/False if interface is in connected state
diff --git a/src/conf_mode/interfaces_wwan.py b/src/conf_mode/interfaces_wwan.py
index 166b857a8..ad6c806ad 100755
--- a/src/conf_mode/interfaces_wwan.py
+++ b/src/conf_mode/interfaces_wwan.py
@@ -149,9 +149,15 @@ def apply(wwan):
         modem = wwan['ifname'].lstrip('wwan')
         base_cmd = f'mmcli --modem {modem}'
         # Number of bearers is limited - always disconnect first
-        cmd(f'{base_cmd} --simple-disconnect')
+        call(f'{base_cmd} --simple-disconnect')
 
     w = WWANIf(wwan['ifname'])
+
+    # We cannot proceed with the configuration if the modem is not detected - so we bail out
+    # and wait for the next cronjob run to re-apply the configuration.
+    if not w.exists(wwan['ifname']):
+        return None
+
     if 'deleted' in wwan or 'disable' in wwan:
         w.remove()