ovsdb: test ovs-vswitchd for backward compatibility

Add test to make sure ovs-vswitchd fall back to use the
"monitor" method when connecting to an older ovsdb-server that
does not support "monitor2".

For testing backward compatibility, add an ovs-appctl command:
"ovsdb-server/disable-monitor2". This command will restart
all currently open jsonrpc connections, but without support for
'monitor2' JSON-RPC method for the new connections.

There is no corresponding enable command, since this feature is only
useful for testing.  'monitor2' will be available when ovsdb-server
restarts.

Signed-off-by: Andy Zhou <azhou@nicira.com>
Acked-by: Ben Pfaff <blp@ovn.org>

3 files changed, 33 insertions, 1 deletions

diff --git a/ovsdb/jsonrpc-server.c b/ovsdb/jsonrpc-server.c
index 53c97cda5..1dcd39429 100644
--- a/ovsdb/jsonrpc-server.c
+++ b/ovsdb/jsonrpc-server.c
@@ -45,6 +45,10 @@ VLOG_DEFINE_THIS_MODULE(ovsdb_jsonrpc_server);
 struct ovsdb_jsonrpc_remote;
 struct ovsdb_jsonrpc_session;
 
+/* Set false to defeature monitor2, causing jsonrpc to respond to monitor2
+ * method with an error.  */
+static bool monitor2_enable__ = true;
+
 /* Message rate-limiting. */
 static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
 
@@ -845,7 +849,7 @@ ovsdb_jsonrpc_session_got_request(struct ovsdb_jsonrpc_session *s,
             reply = execute_transaction(s, db, request);
         }
     } else if (!strcmp(request->method, "monitor") ||
-               !strcmp(request->method, "monitor2")) {
+               (monitor2_enable__ && !strcmp(request->method, "monitor2"))) {
         struct ovsdb *db = ovsdb_jsonrpc_lookup_db(s, request, &reply);
         if (!reply) {
             int l = strlen(request->method) - strlen("monitor");
@@ -1368,3 +1372,10 @@ ovsdb_jsonrpc_monitor_flush_all(struct ovsdb_jsonrpc_session *s)
         }
     }
 }
+
+void
+ovsdb_jsonrpc_disable_monitor2()
+{
+    /* Once disabled, it is not possible to re-enable it. */
+    monitor2_enable__ = false;
+}
diff --git a/ovsdb/jsonrpc-server.h b/ovsdb/jsonrpc-server.h
index fce8b7bd0..7a0bd31b1 100644
--- a/ovsdb/jsonrpc-server.h
+++ b/ovsdb/jsonrpc-server.h
@@ -71,5 +71,6 @@ void ovsdb_jsonrpc_server_get_memory_usage(const struct ovsdb_jsonrpc_server *,
 
 struct ovsdb_jsonrpc_monitor;
 void ovsdb_jsonrpc_monitor_destroy(struct ovsdb_jsonrpc_monitor *);
+void ovsdb_jsonrpc_disable_monitor2(void);
 
 #endif /* ovsdb/jsonrpc-server.h */
diff --git a/ovsdb/ovsdb-server.c b/ovsdb/ovsdb-server.c
index 97b65b658..25fa9c6bf 100644
--- a/ovsdb/ovsdb-server.c
+++ b/ovsdb/ovsdb-server.c
@@ -79,6 +79,7 @@ static unixctl_cb_func ovsdb_server_compact;
 static unixctl_cb_func ovsdb_server_reconnect;
 static unixctl_cb_func ovsdb_server_perf_counters_clear;
 static unixctl_cb_func ovsdb_server_perf_counters_show;
+static unixctl_cb_func ovsdb_server_disable_monitor2;
 
 struct server_config {
     struct sset *remotes;
@@ -329,6 +330,11 @@ main(int argc, char *argv[])
     unixctl_command_register("ovsdb-server/perf-counters-clear", "", 0, 0,
                              ovsdb_server_perf_counters_clear, NULL);
 
+    /* Simulate the behavior of OVS release prior to version 2.5 that
+     * does not support the monitor2 method.  */
+    unixctl_command_register("ovsdb-server/disable-monitor2", "", 0, 0,
+                             ovsdb_server_disable_monitor2, jsonrpc);
+
     main_loop(jsonrpc, &all_dbs, unixctl, &remotes, run_process, &exiting);
 
     ovsdb_jsonrpc_server_destroy(jsonrpc);
@@ -1052,6 +1058,20 @@ ovsdb_server_perf_counters_clear(struct unixctl_conn *conn, int argc OVS_UNUSED,
     unixctl_command_reply(conn, NULL);
 }
 
+/* "ovsdb-server/disable-monitor2": makes ovsdb-server drop all of its
+ * JSON-RPC connections and reconnect. New sessions will not recognize
+ * the 'monitor2' method.   */
+static void
+ovsdb_server_disable_monitor2(struct unixctl_conn *conn, int argc OVS_UNUSED,
+                              const char *argv[] OVS_UNUSED, void *jsonrpc_)
+{
+    struct ovsdb_jsonrpc_server *jsonrpc = jsonrpc_;
+
+    ovsdb_jsonrpc_disable_monitor2();
+    ovsdb_jsonrpc_server_reconnect(jsonrpc);
+    unixctl_command_reply(conn, NULL);
+}
+
 static void
 ovsdb_server_compact(struct unixctl_conn *conn, int argc,
                      const char *argv[], void *dbs_)