AutoInterface: notify_link_change on SLAAC privacy-address rotation

src/main.cpp

@@ -138,6 +138,7 @@ unsigned long wifiConnectedAt = 0;
 AutoInterfaceWrapper autoIface;
 bool autoIfaceDeferredStart = false;
 unsigned long autoIfaceDeferredAt = 0;
+unsigned long lastAutoIfaceLinkCheck = 0;
 
 // LXMF diagnostic counters (reset each heartbeat)
 static uint32_t diagTcpSkipEvents = 0;
@@ -1130,6 +1131,22 @@ void loop() {
         }
     }
 
+    // 7.7. AutoInterface link-local rotation watch — covers SLAAC privacy
+    // address rotation while STA stays associated.  notify_link_change()
+    // is idempotent in the library, so polling here is cheap (string
+    // compare, no socket churn) and only does real work on actual change.
+    if (autoIface.isOnline() && wifiSTAConnected &&
+        millis() - lastAutoIfaceLinkCheck >= 2000) {
+        lastAutoIfaceLinkCheck = millis();
+        IPv6Address ll = WiFi.localIPv6();
+        bool isLinkLocal = (ll[0] == 0xfe) && ((ll[1] & 0xc0) == 0x80);
+        if (isLinkLocal) {
+            esp_netif_t* sta = esp_netif_get_handle_from_ifkey("WIFI_STA_DEF");
+            uint32_t scope = sta ? esp_netif_get_netif_impl_index(sta) : 1;
+            autoIface.notifyLinkChange(ll.toString(), scope);
+        }
+    }
+
     // 8. WiFi + TCP loops (with global budget) — skip only if RNS severely overloaded
     {
         bool skipTcp = (rnsDuration > 500);

src/transport/AutoInterfaceWrapper.cpp

@@ -58,6 +58,13 @@ void AutoInterfaceWrapper::loop() {
 	if (_started && _wrapper) _wrapper.loop();
 }
 
+void AutoInterfaceWrapper::notifyLinkChange(const String& link_local_addr,
+											uint32_t scope_id) {
+	if (!_started || !_impl) return;
+	if (link_local_addr.length() == 0) return;
+	_impl->notify_link_change(link_local_addr.c_str(), scope_id);
+}
+
 bool AutoInterfaceWrapper::isOnline() const {
 	return _started && _wrapper && _wrapper.online();
 }

src/transport/AutoInterfaceWrapper.h

@@ -14,7 +14,10 @@
  *   1. wifi STA connects → resolve link-local IPv6 + scope id
  *   2. wrapper.start(group_id, max_peers, link_local, scope_id)
  *   3. wrapper.loop() each main-loop tick
- *   4. on STA disconnect → wrapper.stop()
+ *   4. periodically poll WiFi.localIPv6() and call notifyLinkChange() —
+ *      catches SLAAC privacy-address rotation while STA stays associated;
+ *      idempotent at the library layer (no socket churn unless changed)
+ *   5. on STA disconnect → wrapper.stop()
  */
 class AutoInterfaceWrapper {
 public:
@@ -24,6 +27,7 @@ public:
 			   uint32_t scope_id);
 	void stop();
 	void loop();
+	void notifyLinkChange(const String& link_local_addr, uint32_t scope_id);
 
 	bool   isOnline()    const;
 	size_t peerCount()   const;