From 33d5effbdc76bba146a131f9ac0ba890413e7197 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C4=99drzej=20Stuczy=C5=84ski?=
 <jedrzej.stuczynski@gmail.com>
Date: Wed, 25 Nov 2020 15:09:40 +0000
Subject: [PATCH] Putting initial packet onto the queue when establishing
 connection (#471)

---
 .../client-libs/mixnet-client/src/client.rs   | 28 +++++++++++++------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/common/client-libs/mixnet-client/src/client.rs b/common/client-libs/mixnet-client/src/client.rs
index 4184c223e5..44f8e68268 100644
--- a/common/client-libs/mixnet-client/src/client.rs
+++ b/common/client-libs/mixnet-client/src/client.rs
@@ -151,8 +151,17 @@ impl Client {
         }
     }
 
-    fn make_connection(&mut self, address: NymNodeRoutingAddress) {
-        let (sender, receiver) = mpsc::channel(self.config.maximum_connection_buffer_size);
+    fn make_connection(
+        &mut self,
+        address: NymNodeRoutingAddress,
+        pending_packet: FramedSphinxPacket,
+    ) {
+        let (mut sender, receiver) = mpsc::channel(self.config.maximum_connection_buffer_size);
+
+        // this CAN'T fail because we just created the channel which has a non-zero capacity
+        if self.config.maximum_connection_buffer_size > 0 {
+            sender.try_send(pending_packet).unwrap();
+        }
 
         // if we already tried to connect to `address` before, grab the current attempt count
         let current_reconnection_attempt = if let Some(existing) = self.conn_new.get_mut(&address) {
@@ -198,13 +207,14 @@ impl Client {
         packet_mode: PacketMode,
     ) -> io::Result<()> {
         trace!("Sending packet to {:?}", address);
+        let framed_packet = FramedSphinxPacket::new(packet, packet_mode);
 
         if let Some(sender) = self.conn_new.get_mut(&address) {
-            let framed_packet = FramedSphinxPacket::new(packet, packet_mode);
             if let Err(err) = sender.channel.try_send(framed_packet) {
                 if err.is_full() {
                     debug!("Connection to {} seems to not be able to handle all the traffic - dropping the current packet", address);
-                    // it's not a 'big' error, but we did not manage to send  the packet
+                    // it's not a 'big' error, but we did not manage to send the packet
+                    // if the queue is full, we can't really do anything but to drop the packet
                     Err(io::Error::new(
                         io::ErrorKind::WouldBlock,
                         "connection queue is full",
@@ -214,8 +224,9 @@ impl Client {
                         "Connection to {} seems to be dead. attempting to re-establish it...",
                         address
                     );
-                    self.make_connection(address);
-                    // it's not a 'big' error, but we did not manage to send the packet
+                    // it's not a 'big' error, but we did not manage to send the packet, but queue
+                    // it up to send it as soon as the connection is re-established
+                    self.make_connection(address, err.into_inner());
                     Err(io::Error::new(
                         io::ErrorKind::ConnectionAborted,
                         "reconnection attempt is in progress",
@@ -233,8 +244,9 @@ impl Client {
         } else {
             // there was never a connection to begin with
             debug!("establishing initial connection to {}", address);
-            self.make_connection(address);
-            // it's not a 'big' error, but we did not manage to send the packet
+            // it's not a 'big' error, but we did not manage to send the packet, but queue the packet
+            // for sending for as soon as the connection is created
+            self.make_connection(address, framed_packet);
             Err(io::Error::new(
                 io::ErrorKind::NotConnected,
                 "connection is in progress",