fix: rebind CWMP session when CPE sends empty POST on new TCP port

TR-069 CPEs routinely open a new TCP connection (new port) for the empty
POST that follows InformResponse. ensureSessionForRemote() only did an
exact remoteKey match, so hasSession() returned false and the state
machine was never continued — GPN discovery was never triggered.

Add IP-only fallback in ensureSessionForRemote(): when the exact
remoteKey is not found, scan RUNNING machines for a unique IP match,
rebind the new remoteKey, and remap sessionMachines to the new sessionId.
Ambiguous cases (NAT/CGNAT with multiple active devices on same IP)
return false safely.

app/services/cwmp/state_machine_manager.ts

@@ -322,11 +322,46 @@ export class StateMachineManager extends EventEmitter {
   }
 
   /**
-   * Ensure session is bound when TCP connection changes
+   * Ensure session is bound when TCP connection changes.
+   *
+   * First tries an exact remoteKey match. If that fails (CPE opened a new TCP
+   * port for the empty POST — standard TR-069 behaviour), falls back to an
+   * IP-only match among RUNNING machines (single unambiguous candidate only).
+   * In both cases the new sessionId is registered in sessionMachines so that
+   * hasSession() returns true and continue() can run.
    */
   ensureSessionForRemote(remoteKey: string, newSession: string): boolean {
-    const deviceKey = this.remoteToDevice.get(remoteKey)
-    if (!deviceKey) return false
+    // --- Exact match path ---
+    let deviceKey = this.remoteToDevice.get(remoteKey)
+
+    // --- IP-only fallback (CPE reconnected on a new TCP port) ---
+    if (!deviceKey) {
+      const lastColon = remoteKey.lastIndexOf(':')
+      const remoteIp = lastColon > 0 ? remoteKey.slice(0, lastColon).replace(/^\[|\]$/g, '') : remoteKey
+
+      const candidates: string[] = []
+      for (const [key, dkJson] of this.remoteToDevice.entries()) {
+        const kLastColon = key.lastIndexOf(':')
+        const keyIp = (kLastColon > 0 ? key.slice(0, kLastColon) : key).replace(/^\[|\]$/g, '')
+        if (keyIp !== remoteIp) continue
+
+        const existSession = this.deviceSessions.get(dkJson)
+        if (!existSession) continue
+        const mid = this.sessionMachines.get(existSession)
+        if (!mid) continue
+        const m = this.machines.get(mid)
+        if (!m || m.status !== MachineStatus.RUNNING) continue
+
+        if (!candidates.includes(dkJson)) candidates.push(dkJson)
+      }
+
+      // Refuse to guess if ambiguous (NAT/CGNAT with multiple active devices)
+      if (candidates.length !== 1) return false
+      deviceKey = candidates[0]
+
+      // Register the new remoteKey so future lookups (exact or fallback) hit immediately
+      this.bindRemoteToDevice(remoteKey, JSON.parse(deviceKey))
+    }
 
     const existingSession = this.deviceSessions.get(deviceKey)
     if (!existingSession) return false
@@ -338,15 +373,17 @@ export class StateMachineManager extends EventEmitter {
     if (!machine) return false
 
     // Don't rebind to a completed/failed machine
-    if (machine.status !== MachineStatus.RUNNING) {
-      return false
-    }
+    if (machine.status !== MachineStatus.RUNNING) return false
 
     if (existingSession !== newSession) {
       this.sessionMachines.delete(existingSession)
       this.sessionMachines.set(newSession, machineId)
       this.deviceSessions.set(deviceKey, newSession)
       machine.session = newSession
+      logger.debug(
+        { oldSession: existingSession, newSession, deviceKey },
+        '[StateMachineManager] Session rebound via IP fallback (CPE new TCP port)'
+      )
     }
 
     return true