Avoid closing connection on channel EOF (#816)

libp2p/muxers/mplex/lpchannel.nim

@@ -244,7 +244,11 @@ proc completeWrite(
   except CancelledError as exc:
     # Chronos may still send the data
     raise exc
-  except LPStreamClosedError as exc:
+  except LPStreamConnDownError as exc:
+    await s.reset()
+    await s.conn.close()
+    raise exc
+  except LPStreamEOFError as exc:
     raise exc
   except CatchableError as exc:
     trace "exception in lpchannel write handler", s, msg = exc.msg

libp2p/muxers/mplex/mplex.nim

@@ -177,8 +177,14 @@ method handle*(m: Mplex) {.async, gcsafe.} =
             raise newLPStreamLimitError()
 
           trace "pushing data to channel", m, channel, len = data.len
+          try:
             await channel.pushData(data)
             trace "pushed data to channel", m, channel, len = data.len
+          except LPStreamClosedError as exc:
+            # Channel is being closed, but `cleanupChann` was not yet triggered.
+            trace "pushing data to channel failed", m, channel, len = data.len,
+              msg = exc.msg
+            discard  # Ignore message, same as if `cleanupChann` had completed.
 
         of MessageType.CloseIn, MessageType.CloseOut:
           await channel.pushEof()