natpmp: pass shared pointer to timer to avoid crash

Change-Id: I1fbf84f8fb10b14390abb951b8ed312716047936

src/upnp/protocol/natpmp/nat_pmp.cpp

@@ -186,9 +186,11 @@ NatPmp::searchForIgd()
 
             // Cancel the current timer (if any) and re-schedule.
             searchForIgdTimer_.expires_after(NATPMP_SEARCH_RETRY_UNIT * igdSearchCounter_);
-            searchForIgdTimer_.async_wait([this](const asio::error_code& ec) {
-                if (!ec)
-                    searchForIgd();
+            searchForIgdTimer_.async_wait([w=weak()](const asio::error_code& ec) {
+                if (!ec) {
+                    if (auto shared = w.lock())
+                        shared->searchForIgd();
+                }
             });
         } else {
             if (logger_) logger_->warn("NAT-PMP: Setup failed after {} trials. NAT-PMP will be disabled!",

src/upnp/protocol/natpmp/nat_pmp.h

@@ -149,6 +149,13 @@ private:
 
     // Shutdown synchronization
     bool shutdownComplete_ {false};
+
+    // Asio :(
+    // https://stackoverflow.com/questions/35507956/is-it-safe-to-destroy-boostasio-timer-from-its-handler-or-handler-dtor
+    std::weak_ptr<NatPmp> weak()
+    {
+        return std::static_pointer_cast<NatPmp>(shared_from_this());
+    }
 };
 
 } // namespace upnp