+ * for states to allow testing for more than one state with a bit mask.
+ *
+ * The STP_DISABLED state means that the port is disabled by management.
+ * In our implementation, this state means that the port does not
+ * participate in the spanning tree, but it still forwards traffic as if
+ * it were in the STP_FORWARDING state. This may be different from
+ * other implementations.
+ *
+ * The following diagram describes the various states and what they are
+ * allowed to do in OVS:
+ *
+ * FWD LRN TX_BPDU RX_BPDU
+ * --- --- ------- -------
+ * Disabled Y - - -
+ * Blocking - - - Y
+ * Listening - - Y Y
+ * Learning - Y Y Y
+ * Forwarding Y Y Y Y
+ *
+ * Once again, note that the disabled state forwards traffic, which is
+ * likely different than the spec would indicate.
+ */