Merge bitcoin/bitcoin#29352: test: fix intermittent failure in p2p_v2_earlykeyresponse

9642aef test: fix intermittent failure in p2p_v2_earlykeyresponse (Martin Zumsande)

Pull request description:

  The test fails intermittently, see https://cirrus-ci.com/task/6403578080788480?logs=ci#L3521 and bitcoin/bitcoin#24748 (comment).
  I think it's because of a race between the python NetworkThread and the actual
  test, which will both call `initiate_v2_handshake`. I could reproduce it by adding a sleep into `initiate_v2_handshake` after the line `self.sent_garbage = random.randbytes(garbage_len)`.

  Fix this by waiting for the first `initiate_v2_handshake` to have finished before calling it a second time.

ACKs for top commit:
  stratospher:
    tested ACK 9642aef.
  achow101:
    ACK 9642aef
  theStack:
    Tested ACK 9642aef

Tree-SHA512: f728bbceaf816ddefeee4957494ccb608ad4fc912cb5cbf5f2acf09836df969c4e8fa2bb441aadb94fa39b3ffbb005d4132e7b6a5a98d80811810d8bd1d624e3

Author: achow101

test/functional/p2p_v2_earlykeyresponse.py

@@ -49,6 +49,7 @@ class PeerEarlyKey(P2PInterface):
     def __init__(self):
         super().__init__()
         self.v2_state = None
+        self.connection_opened = False
 
     def connection_made(self, transport):
         """64 bytes ellswift is sent in 2 parts during `initial_v2_handshake()`"""
@@ -59,6 +60,8 @@ def data_received(self, t):
         # check that data can be received on recvbuf only when mismatch from V1_PREFIX happens (send_net_magic = False)
         assert self.v2_state.can_data_be_received and not self.v2_state.send_net_magic
 
+    def on_open(self):
+        self.connection_opened = True
 
 class P2PEarlyKey(BitcoinTestFramework):
     def set_test_params(self):
@@ -73,6 +76,7 @@ def run_test(self):
         self.log.info('If a response is received, assertion failure would happen in our custom data_received() function')
         # send happens in `initiate_v2_handshake()` in `connection_made()`
         peer1 = node0.add_p2p_connection(PeerEarlyKey(), wait_for_verack=False, send_version=False, supports_v2_p2p=True)
+        self.wait_until(lambda: peer1.connection_opened)
         self.log.info('Sending remaining ellswift and garbage which are different from V1_PREFIX. Since a response is')
         self.log.info('expected now, our custom data_received() function wouldn\'t result in assertion failure')
         ellswift_and_garbage_data = peer1.v2_state.initiate_v2_handshake()