return error rather than panic when merging socket during shutdown

or to fallible gateway

common/client-core/src/client/mix_traffic/mod.rs

@@ -96,24 +96,45 @@ impl MixTrafficController {
         mut mix_packets: Vec<MixPacket>,
     ) -> Result<(), ErasedGatewayError> {
         debug_assert!(!mix_packets.is_empty());
-
-        let result = if mix_packets.len() == 1 {
+        let send_future = if mix_packets.len() == 1 {
             let mix_packet = mix_packets.pop().unwrap();
-            self.gateway_transceiver.send_mix_packet(mix_packet).await
+            self.gateway_transceiver.send_mix_packet(mix_packet)
         } else {
-            self.gateway_transceiver
-                .batch_send_mix_packets(mix_packets)
-                .await
+            self.gateway_transceiver.batch_send_mix_packets(mix_packets)
         };
 
-        if result.is_err() {
-            self.consecutive_gateway_failure_count += 1;
-        } else {
-            trace!("We *might* have managed to forward sphinx packet(s) to the gateway!");
-            self.consecutive_gateway_failure_count = 0;
-        }
+        tokio::select! {
+            biased;
+            _ = self.task_client.recv() => {
+                trace!("received shutdown while handling messages");
+                Ok(())
+            }
+            result = send_future => {
+                if result.is_err() {
+                    self.consecutive_gateway_failure_count += 1;
+                } else {
+                    trace!("We *might* have managed to forward sphinx packet(s) to the gateway!");
+                    self.consecutive_gateway_failure_count = 0;
+                }
 
-        result
+                result
+            }
+        }
+    }
+
+    async fn on_client_request(&mut self, client_request: ClientRequest) {
+        tokio::select! {
+            biased;
+             _ = self.task_client.recv() => {
+                trace!("received shutdown while handling client request");
+                return
+            }
+            result = self.gateway_transceiver.send_client_request(client_request) => {
+                if let Err(err) = result {
+                    error!("Failed to send client request: {err}")
+                }
+            }
+        }
     }
 
     pub fn start(mut self) {
@@ -122,6 +143,11 @@ impl MixTrafficController {
 
             while !self.task_client.is_shutdown() {
                 tokio::select! {
+                    biased;
+                    _ = self.task_client.recv() => {
+                        tracing::trace!("MixTrafficController: Received shutdown");
+                        break;
+                    }
                     mix_packets = self.mix_rx.recv() => match mix_packets {
                         Some(mix_packets) => {
                             if let Err(err) = self.on_messages(mix_packets).await {
@@ -144,19 +170,12 @@ impl MixTrafficController {
                     },
                     client_request = self.client_rx.recv() => match client_request {
                         Some(client_request) => {
-                            match self.gateway_transceiver.send_client_request(client_request).await {
-                                Ok(_) => (),
-                                Err(e) => error!("Failed to send client request: {e}"),
-                            };
+                            self.on_client_request(client_request).await;
                         },
                         None => {
                             tracing::trace!("MixTrafficController, client request channel closed");
                         }
                     },
-                    _ = self.task_client.recv() => {
-                        tracing::trace!("MixTrafficController: Received shutdown");
-                        break;
-                    }
                 }
             }
             self.task_client.recv_timeout().await;

common/client-core/src/client/real_messages_control/acknowledgement_control/input_message_listener.rs

@@ -223,6 +223,11 @@ where
 
         while !self.task_client.is_shutdown() {
             tokio::select! {
+                biased;
+                _ = self.task_client.recv() => {
+                    tracing::trace!("InputMessageListener: Received shutdown");
+                    break;
+                }
                 input_msg = self.input_receiver.recv() => match input_msg {
                     Some(input_msg) => {
                         self.on_input_message(input_msg).await;
@@ -232,9 +237,7 @@ where
                         break;
                     }
                 },
-                _ = self.task_client.recv() => {
-                    tracing::trace!("InputMessageListener: Received shutdown");
-                }
+
             }
         }
         self.task_client.recv_timeout().await;

common/client-core/src/client/real_messages_control/acknowledgement_control/retransmission_request_listener.rs

@@ -179,6 +179,11 @@ where
 
         while !self.task_client.is_shutdown() {
             tokio::select! {
+                biased;
+                 _ = self.task_client.recv() => {
+                    tracing::trace!("RetransmissionRequestListener: Received shutdown");
+                    break;
+                }
                 timed_out_ack = self.request_receiver.next() => match timed_out_ack {
                     Some(timed_out_ack) => self.on_retransmission_request(timed_out_ack, packet_type).await,
                     None => {
@@ -186,9 +191,7 @@ where
                         break;
                     }
                 },
-                _ = self.task_client.recv() => {
-                    tracing::trace!("RetransmissionRequestListener: Received shutdown");
-                }
+
             }
         }
         self.task_client.recv_timeout().await;

common/client-core/src/client/real_messages_control/message_handler.rs

@@ -535,6 +535,7 @@ where
             pending_acks.push(pending_ack);
         }
 
+        drop(topology_permit);
         self.insert_pending_acks(pending_acks);
         self.forward_messages(real_messages, lane).await;
 
@@ -716,17 +717,22 @@ where
 
     // tells real message sender (with the poisson timer) to send this to the mix network
     pub(crate) async fn forward_messages(
-        &self,
+        &mut self,
         messages: Vec<RealMessage>,
         transmission_lane: TransmissionLane,
     ) {
-        if let Err(err) = self
-            .real_message_sender
-            .send((messages, transmission_lane))
-            .await
-        {
-            if !self.task_client.is_shutdown_poll() {
-                error!("Failed to forward messages to the real message sender: {err}");
+        tokio::select! {
+            biased;
+            _ = self.task_client.recv() => {
+                trace!("received shutdown while attempting to forward mixnet messages");
+                return;
+            }
+            sending_res = self.real_message_sender.send((messages, transmission_lane)) => {
+                if sending_res.is_err() {
+                    error!(
+                        "failed to forward mixnet messages due to closed channel (outside of shutdown!)"
+                    );
+                }
             }
         }
     }

common/client-core/src/client/real_messages_control/real_traffic_stream.rs

@@ -278,17 +278,33 @@ where
             }
         };
 
-        if let Err(err) = self.mix_tx.send(vec![next_message]).await {
-            if !self.task_client.is_shutdown_poll() {
-                tracing::error!("Failed to send: {err}");
+        let sending_res = tokio::select! {
+            biased;
+            _ = self.task_client.recv() => {
+                trace!("received shutdown signal while attempting to send mix message");
+                return
+            }
+            sending_res = self.mix_tx.send(vec![next_message]) => {
+                sending_res
+            }
+        };
+
+        match sending_res {
+            Err(_) => {
+                if !self.task_client.is_shutdown_poll() {
+                    tracing::error!(
+                        "failed to send mixnet packet due to closed channel (outside of shutdown!)"
+                    );
+                }
+            }
+            Ok(_) => {
+                let event = if fragment_id.is_some() {
+                    PacketStatisticsEvent::RealPacketSent(packet_size)
+                } else {
+                    PacketStatisticsEvent::CoverPacketSent(packet_size)
+                };
+                self.stats_tx.report(event.into());
             }
-        } else {
-            let event = if fragment_id.is_some() {
-                PacketStatisticsEvent::RealPacketSent(packet_size)
-            } else {
-                PacketStatisticsEvent::CoverPacketSent(packet_size)
-            };
-            self.stats_tx.report(event.into());
         }
 
         // notify ack controller about sending our message only after we actually managed to push it

common/client-core/src/lib.rs

@@ -25,6 +25,7 @@ where
     wasm_bindgen_futures::spawn_local(future);
 }
 
+#[track_caller]
 #[cfg(not(target_arch = "wasm32"))]
 pub(crate) fn spawn_future<F>(future: F)
 where

common/client-libs/gateway-client/src/client/mod.rs

@@ -201,7 +201,7 @@ impl<C, St> GatewayClient<C, St> {
     #[cfg(not(target_arch = "wasm32"))]
     pub async fn establish_connection(&mut self) -> Result<(), GatewayClientError> {
         debug!(
-            "Attemting to establish connection to gateway at: {}",
+            "Attempting to establish connection to gateway at: {}",
             self.gateway_address
         );
         let (ws_stream, _) = connect_async(

common/client-libs/gateway-client/src/socket_state.rs

@@ -337,7 +337,7 @@ impl PartiallyDelegatedHandle {
         // check if the split stream didn't error out
         let receive_res = stream_receiver
             .try_recv()
-            .expect("stream sender was somehow dropped without sending anything!");
+            .map_err(|_| GatewayClientError::ConnectionAbruptlyClosed)?;
 
         if let Some(res) = receive_res {
             let _res = res?;

common/task/src/spawn.rs

@@ -10,6 +10,7 @@ where
 }
 
 #[cfg(not(target_arch = "wasm32"))]
+#[track_caller]
 pub fn spawn<F>(future: F)
 where
     F: Future + Send + 'static,
@@ -18,6 +19,7 @@ where
     tokio::spawn(future);
 }
 
+#[track_caller]
 pub fn spawn_with_report_error<F, T, E>(future: F, mut shutdown: TaskClient)
 where
     F: Future<Output = Result<T, E>> + Send + 'static,