fix: address five review findings (NM retry loop, start_display message, code quality)

- wifi_monitor_daemon: reset _consecutive_internet_failures = 0 in both
  NM-restart exception handlers; previously both left the counter at threshold,
  causing an immediate retry on the next iteration instead of waiting another
  full backoff period

- api_v3: fix start_display failure message — when mode is set and systemctl
  returns non-zero, message now includes the failure reason and a hint rather
  than always reporting success phrasing

- wifi_manager: move _redirect_backend from class variable to instance variable
  in __init__ alongside _ap_enabled_at; class-level default shadowed correctly
  in practice (single instance) but was misleading

- wifi_manager: narrow broad except Exception in _check_internet_connectivity
  to (subprocess.SubprocessError, OSError) for ping and OSError for HTTP
  (urllib.error.URLError is an OSError subclass in Python 3)

- wifi_manager: remove redundant local 'import re as _re' in _validate_ap_config;
  re is already imported at module level (line 37)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/utils/wifi_monitor_daemon.py

@@ -153,10 +153,12 @@ class WiFiMonitorDaemon:
                                 self.wifi_manager._disconnected_checks = 0
                             except subprocess.CalledProcessError as e:
                                 logger.error(f"NetworkManager restart failed (rc={e.returncode}); "
-                                             "keeping failure counter unchanged")
+                                             "resetting failure counter to avoid tight retry loop")
+                                self._consecutive_internet_failures = 0
                             except Exception as e:
                                 logger.error(f"NetworkManager restart error: {e}; "
-                                             "keeping failure counter unchanged")
+                                             "resetting failure counter to avoid tight retry loop")
+                                self._consecutive_internet_failures = 0
                     else:
                         self._consecutive_internet_failures = 0
                 else:

src/wifi_manager.py

@@ -144,6 +144,8 @@ class WiFiManager:
 
         # Timestamp set when AP mode is enabled; used for the idle-timeout check
         self._ap_enabled_at: Optional[float] = None
+        # Which redirect backend was used (iptables/nftables/None); set per-instance
+        self._redirect_backend: Optional[str] = None
 
         logger.info(f"WiFi Manager initialized - nmcli: {self.has_nmcli}, iwlist: {self.has_iwlist}, "
                    f"hostapd: {self.has_hostapd}, dnsmasq: {self.has_dnsmasq}, "
@@ -691,9 +693,8 @@ class WiFiManager:
 
     def _validate_ap_config(self) -> Tuple[str, int]:
         """Return a sanitized (ssid, channel) pair from config, falling back to defaults."""
-        import re as _re
         ssid = str(self.config.get("ap_ssid", DEFAULT_AP_SSID))
-        if not ssid or len(ssid) > 32 or not _re.match(r'^[\x20-\x7E]+$', ssid):
+        if not ssid or len(ssid) > 32 or not re.match(r'^[\x20-\x7E]+$', ssid):
             logger.warning(f"AP SSID '{ssid}' is invalid, falling back to default")
             ssid = DEFAULT_AP_SSID
         try:
@@ -705,10 +706,6 @@ class WiFiManager:
             channel = DEFAULT_AP_CHANNEL
         return ssid, channel
 
-    # Tracks which redirect backend was used so teardown uses the same one.
-    # Value is "iptables", "nftables", or None (not set up).
-    _redirect_backend: Optional[str] = None
-
     def _setup_iptables_redirect(self) -> bool:
         """
         Add port 80 → 5000 redirect rules for the captive portal.
@@ -936,14 +933,14 @@ class WiFiManager:
             if r.returncode == 0:
                 logger.debug("Internet connectivity confirmed via ping 8.8.8.8")
                 return True
-        except Exception:
+        except (subprocess.SubprocessError, OSError):
             pass
         try:
             import urllib.request as _ureq
             _ureq.urlopen("http://connectivity-check.ubuntu.com/", timeout=timeout)
             logger.debug("Internet connectivity confirmed via HTTP check")
             return True
-        except Exception:
+        except OSError:
             pass
         logger.debug("Internet connectivity check failed (both ping and HTTP)")
         return False

web_interface/blueprints/api_v3.py

@@ -1720,7 +1720,8 @@ def execute_system_action():
                                      capture_output=True, text=True, timeout=15)
                 return jsonify({
                     'status': 'success' if result.returncode == 0 else 'error',
-                    'message': f'Started display in {mode} mode',
+                    'message': f'Started display in {mode} mode' if result.returncode == 0
+                               else f'Failed to start display in {mode} mode: {result.stderr.strip() or "check sudo systemctl status ledmatrix.service"}',
                     'returncode': result.returncode,
                     'stdout': result.stdout,
                     'stderr': result.stderr