fix(rumqttd): set default network timeout as Duration::MAX instead of zero. (#949)

Author: Ddystopia

rumqttd/CHANGELOG.md

@@ -25,6 +25,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 - MQTT keep alive interval
+- Change default network keep alive interval from `Duration::ZERO` to `Duration::MAX`.
 - record client id for remote link's span
 - session present flag in connack
 - Make write method return the number of bytes written correctly everywhere

rumqttd/src/link/network.rs

@@ -55,7 +55,10 @@ impl<P: Protocol> Network<P> {
             write: BytesMut::with_capacity(10 * 1024),
             max_incoming_size,
             max_connection_buffer_len,
-            keepalive: Duration::ZERO,
+            // Overwritten by keepalive value in connect packet, otherwise we
+            // would wait indefinitely until we get a packet / network error
+            // when we call read.
+            keepalive: Duration::MAX,
             protocol,
         }
     }