Merge bitcoin/bitcoin#29356: test: make v2transport arg in addconnection mandatory and few cleanups

e7fd70f4b6 [test] make v2transport arg in addconnection mandatory and few cleanups (stratospher)

Pull request description:

  - make `v2transport` argument in `addconnection` regression-testing only RPC mandatory. https://github.com/bitcoin/bitcoin/pull/24748#discussion_r1470738750
  - previously it was an optional arg with default `false` value.
  - only place this RPC is used is in the [functional tests](11b436a66a/test/functional/test_framework/test_node.py (L742)) where we always pass the appropriate `v2transport` option to the RPC anyways. (and that too just for python dummy peer(`P2PInterface`) and bitcoind(`TestNode`) interactions)
  - rename `v2_handshake()` to `_on_data_v2_handshake()` https://github.com/bitcoin/bitcoin/pull/24748#discussion_r1466958424
  - more compact return statement in `wait_for_reconnect()` https://github.com/bitcoin/bitcoin/pull/24748#discussion_r1466979708
  - assertion to check that empty version packets are received from `TestNode`.

ACKs for top commit:
  glozow:
    ACK e7fd70f4b6
  theStack:
    Code-review ACK e7fd70f4b6
  mzumsande:
    Code Review ACK e7fd70f4b6

Tree-SHA512: e66e29baccd91e1e4398b91f7d45c5fc7c2841d77d8a6178734586017bf2be63496721649da91848dec71da605ee31664352407d5bb896e624cc693767c61a1f

test/functional/test_framework/p2p.py

@@ -242,7 +242,7 @@ class P2PConnection(asyncio.Protocol):
         self.on_close()
 
     # v2 handshake method
-    def v2_handshake(self):
+    def _on_data_v2_handshake(self):
         """v2 handshake performed before P2P messages are exchanged (see BIP324). P2PConnection is the initiator
         (in inbound connections to TestNode) and the responder (in outbound connections from TestNode).
         Performed by:
@@ -298,7 +298,7 @@ class P2PConnection(asyncio.Protocol):
         if len(t) > 0:
             self.recvbuf += t
             if self.supports_v2_p2p and not self.v2_state.tried_v2_handshake:
-                self.v2_handshake()
+                self._on_data_v2_handshake()
             else:
                 self._on_data()
 
@@ -595,9 +595,7 @@ class P2PInterface(P2PConnection):
 
     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
+            return self.is_connected and self.last_message.get('version') and not self.supports_v2_p2p
         self.wait_until(test_function, timeout=timeout, check_connected=False)
 
     # Message receiving helper methods

test/functional/test_framework/v2_p2p.py

@@ -220,6 +220,7 @@ class EncryptedP2PState:
             # decoy packets have contents = None. v2 handshake is complete only when version packet
             # (can be empty with contents = b"") with contents != None is received.
             if contents is not None:
+                assert contents == b""  # currently TestNode sends an empty version packet
                 self.tried_v2_handshake = True
                 return processed_length, True
             response = response[length:]