Handle more cancellations (#733)

* Mplex: handle write cancellation
* LpChannel: Don't close connection on EOF

libp2p/muxers/mplex/lpchannel.nim

@@ -78,6 +78,8 @@ proc open*(s: LPChannel) {.async, gcsafe.} =
   try:
     await s.conn.writeMsg(s.id, MessageType.New, s.name)
     s.isOpen = true
+  except CancelledError as exc:
+    raise exc
   except CatchableError as exc:
     await s.conn.close()
     raise exc
@@ -221,6 +223,11 @@ proc completeWrite(
         libp2p_protocols_bytes.inc(msgLen.int64, labelValues=[s.tag, "out"])
 
     s.activity = true
+  except CancelledError as exc:
+    # Chronos may still send the data
+    raise exc
+  except LPStreamClosedError as exc:
+    raise exc
   except CatchableError as exc:
     trace "exception in lpchannel write handler", s, msg = exc.msg
     await s.reset()

libp2p/protocols/secure/secure.nim

@@ -152,6 +152,8 @@ method readOnce*(s: SecureConn,
       s.isEof = true
       await s.close()
       raise err
+    except CancelledError as exc:
+      raise exc
     except CatchableError as err:
       debug "Error while reading message from secure connection, closing.",
         error = err.name,

libp2p/stream/bufferstream.nim

@@ -134,6 +134,10 @@ method readOnce*(s: BufferStream,
     let buf =
       try:
         await s.readQueue.popFirst()
+      except CancelledError as exc:
+        # Not very efficient, but shouldn't happen often
+        s.readBuf.assign(@(p.toOpenArray(0, rbytes - 1)) & @(s.readBuf.data))
+        raise exc
       except CatchableError as exc:
         # When an exception happens here, the Bufferstream is effectively
         # broken and no more reads will be valid - for now, return EOF if it's