fix handling of messages with packet id 0

Messages with packet id 0 should be handled differently as they won't receive a PubAck or PubRec control messages hence it will never be removed from the hashmap and future messages with packet id 0 are ignored

Signed-off-by: Reuben Miller <reuben.d.miller@gmail.com>

crates/extensions/tedge_mqtt_bridge/src/lib.rs

@@ -377,7 +377,23 @@ async fn half_bridge(
 
             // Keep track of packet IDs so we can acknowledge messages
             Event::Outgoing(Outgoing::Publish(pkid)) => {
-                if let hash_map::Entry::Vacant(e) = forward_pkid_to_received_msg.entry(pkid) {
+                if pkid == 0 {
+                    // Messages with pkid 0 (meaning QoS=0) should not be added to the hashmap
+                    // as multiple messages with the pkid=0 can be received
+                    match companion_bridge_half.recv().await {
+                        // A message was forwarded by the other bridge half, note the packet id
+                        Some(Some((topic, msg))) => {
+                            loop_breaker.forward_on_topic(topic, &msg);
+                        }
+
+                        // A healthcheck message was published, ignore this packet id
+                        Some(None) => {}
+
+                        // The other bridge half has disconnected, break the loop and shut down the bridge
+                        None => break,
+                    }
+                } else if let hash_map::Entry::Vacant(e) = forward_pkid_to_received_msg.entry(pkid)
+                {
                     match companion_bridge_half.recv().await {
                         // A message was forwarded by the other bridge half, note the packet id
                         Some(Some((topic, msg))) => {