vswitchd: Document what changes to the database flush the flow table.

Requested-by: Hao Zheng <hzheng@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>

diff --git a/vswitchd/vswitch.xml b/vswitchd/vswitch.xml
index 84d91da..2f9a534 100644 (file)
--- a/vswitchd/vswitch.xml
+++ b/vswitchd/vswitch.xml
@@ -372,8 +372,20 @@
 
     <group title="OpenFlow Configuration">
       <column name="controller">
-        OpenFlow controller set.  If unset, then no OpenFlow controllers
-        will be used.
+        <p>
+          OpenFlow controller set.  If unset, then no OpenFlow controllers
+          will be used.
+        </p>
+
+        <p>
+          If there are primary controllers, removing all of them clears the
+          flow table.  If there are no primary controllers, adding one also
+          clears the flow table.  Other changes to the set of controllers, such
+          as adding or removing a service controller, adding another primary
+          controller to supplement an existing primary controller, or removing
+          only one of two primary controllers, have no effect on the flow
+          table.
+        </p>
       </column>
 
       <column name="fail_mode">
@@ -406,6 +418,10 @@
         <p>When more than one controller is configured,
         <ref column="fail_mode"/> is considered only when none of the
         configured controllers can be contacted.</p>
+        <p>
+          Changing <ref column="fail_mode"/> when no primary controllers are
+          configured clears the flow table.
+        </p>
       </column>
 
       <column name="datapath_id">