add ErrTransientConn error
@@ -8,3 +8,7 @@ var ErrNoRemoteAddrs = errors.New("no remote addresses")
// ErrNoConn is returned when attempting to open a stream to a peer with the NoDial
// option and no usable connection is available.
var ErrNoConn = errors.New("no usable connection to peer")
+
+// ErrTransientConn is returned when attempting to open a stream to a peer with only a transient
+// connection, without specifying the UseTransient option.
+var ErrTransientConn = errors.New("transient connection to peer")
