Fix `connections_test_cft` crashes in multi-threaded CI (#2715)

.threading_canary

@@ -1 +1 @@
-chchirpirpp
+cheep

src/enclave/rpc_sessions.h

@@ -50,7 +50,23 @@ namespace enclave
         enclave::TLSEndpoint(session_id, writer_factory, std::move(ctx))
       {}
 
+      static void recv_cb(std::unique_ptr<threading::Tmsg<SendRecvMsg>> msg)
+      {
+        reinterpret_cast<NoMoreSessionsEndpointImpl*>(msg->data.self.get())
+          ->recv_(msg->data.data.data(), msg->data.data.size());
+      }
+
       void recv(const uint8_t* data, size_t size) override
+      {
+        auto msg = std::make_unique<threading::Tmsg<SendRecvMsg>>(&recv_cb);
+        msg->data.self = this->shared_from_this();
+        msg->data.data.assign(data, data + size);
+
+        threading::ThreadMessaging::thread_messaging.add_task(
+          execution_thread, std::move(msg));
+      }
+
+      void recv_(const uint8_t* data, size_t size)
       {
         recv_buffered(data, size);
 

src/enclave/tls_endpoint.h

@@ -220,7 +220,7 @@ namespace enclave
     {
       if (threading::get_current_thread_id() != execution_thread)
       {
-        throw std::exception();
+        throw std::runtime_error("Called recv_buffered from incorrect thread");
       }
       pending_read.insert(pending_read.end(), data, data + size);
       do_handshake();