+ /* Before 1.5, OpenFlow specified that OFPT_PORT_MOD should not
+ * generate OFPT_PORT_STATUS messages. That requirement was a
+ * relic of how OpenFlow originally supported a single controller,
+ * so that one could expect the controller to already know the
+ * changes it had made.
+ *
+ * EXT-338 changes OpenFlow 1.5 OFPT_PORT_MOD to send
+ * OFPT_PORT_STATUS messages to every controller. This is
+ * obviously more useful in the multi-controller case. We could
+ * always implement it that way in OVS, but that would risk
+ * confusing controllers that are intended for single-controller
+ * use only. (Imagine a controller that generates an OFPT_PORT_MOD
+ * in response to any OFPT_PORT_STATUS!)
+ *
+ * So this compromises: for OpenFlow 1.4 and earlier, it generates
+ * OFPT_PORT_STATUS for OFPT_PORT_MOD, but not back to the
+ * originating controller. In a single-controller environment, in
+ * particular, this means that it will never generate
+ * OFPT_PORT_STATUS for OFPT_PORT_MOD at all. */
+ if (ofconn == source
+ && rconn_get_version(ofconn->rconn) < OFP15_VERSION) {
+ continue;
+ }
+