[test] Check whether v2 TestNode performs downgrading

test/functional/test_framework/p2p.py

@@ -590,6 +590,13 @@ class P2PInterface(P2PConnection):
         test_function = lambda: not self.is_connected
         self.wait_until(test_function, timeout=timeout, check_connected=False)
 
+    def wait_for_reconnect(self, timeout=60):
+        def test_function():
+            if not (self.is_connected and self.last_message.get('version') and self.v2_state is None):
+                return False
+            return True
+        self.wait_until(test_function, timeout=timeout, check_connected=False)
+
     # Message receiving helper methods
 
     def wait_for_tx(self, txid, timeout=60):

test/functional/test_framework/test_node.py

@@ -736,6 +736,9 @@ class TestNode():
         supports_v2_p2p = supports_v2_p2p and advertise_v2_p2p
         p2p_conn.peer_accept_connection(connect_cb=addconnection_callback, connect_id=p2p_idx + 1, net=self.chain, timeout_factor=self.timeout_factor, supports_v2_p2p=supports_v2_p2p, reconnect=reconnect, **kwargs)()
 
+        if reconnect:
+            p2p_conn.wait_for_reconnect()
+
         if connection_type == "feeler":
             # feeler connections are closed as soon as the node receives a `version` message
             p2p_conn.wait_until(lambda: p2p_conn.message_count["version"] == 1, check_connected=False)