Merge bitcoin/bitcoin#30394: net: fix race condition in self-connect detection

16bd283b3ad05daa41259a062aee0fc05b463fa6 Reapply "test: p2p: check that connecting to ourself leads to disconnect" (Sebastian Falbesoner)
0dbcd4c14855fe2cba15a32245572b693dc18c4e net: prevent sending messages in `NetEventsInterface::InitializeNode` (Sebastian Falbesoner)
66673f1c1302c986e344c7f44bb0b352213d5dc8 net: fix race condition in self-connect detection (Sebastian Falbesoner)

Pull request description:

  This PR fixes a recently discovered race condition in the self-connect detection (see #30362 and #30368).

  Initiating an outbound network connection currently involves the following steps after the socket connection is established (see [`CConnman::OpenNetworkConnection`](https://github.com/bitcoin/bitcoin/blob/bd5d1688b4311e21c0e0ff89a3ae02ef7d0543b8/src/net.cpp#L2923-L2930) method):
  1. set up node state
  2. queue VERSION message (both steps 1 and 2 happen in [`InitializeNode`](https://github.com/bitcoin/bitcoin/blob/bd5d1688b4311e21c0e0ff89a3ae02ef7d0543b8/src/net_processing.cpp#L1662-L1683))
  3. add new node to vector `m_nodes`

  If we connect to ourself, it can happen that the sent VERSION message (step 2) is received and processed locally *before* the node object is added to the connection manager's `m_nodes` vector (step 3). In this case, the self-connect remains undiscovered, as the detection doesn't find the outbound peer in `m_nodes` yet (see `CConnman::CheckIncomingNonce`).

  Fix this by swapping the order of 2. and 3., by taking the `PushNodeVersion` call out of `InitializeNode` and doing that in the `SendMessages` method instead, which is only called for `CNode` instances in `m_nodes`.

  The temporarily reverted test introduced in #30362 is readded. Fixes #30368.

  Thanks go to vasild, mzumsande and dergoegge for suggestions on how to fix this (see https://github.com/bitcoin/bitcoin/issues/30368#issuecomment-2200625017 ff. and https://github.com/bitcoin/bitcoin/pull/30394#discussion_r1668290789).

ACKs for top commit:
  naiyoma:
    tested ACK [https://github.com/bitcoin/bitcoin/pull/30394/commits/16bd283b3ad05daa41259a062aee0fc05b463fa6](https://github.com/bitcoin/bitcoin/pull/30394/commits/16bd283b3ad05daa41259a062aee0fc05b463fa6),  built and tested locally,  test passes successfully.
  mzumsande:
    ACK 16bd283b3ad05daa41259a062aee0fc05b463fa6
  tdb3:
    ACK 16bd283b3ad05daa41259a062aee0fc05b463fa6
  glozow:
    ACK 16bd283b3ad05daa41259a062aee0fc05b463fa6
  dergoegge:
    ACK 16bd283b3ad05daa41259a062aee0fc05b463fa6

Tree-SHA512: 5b8aced6cda8deb38d4cd3fe4980b8af505d37ffa0925afaa734c5d81efe9d490dc48a42e1d0d45dd2961c0e1172a3d5b6582ae9a2d642f2592a17fbdc184445

1 files changed, 6 insertions, 3 deletions

diff --git a/test/functional/p2p_handshake.py b/test/functional/p2p_handshake.py
index 21959ae522..9536e74893 100755
--- a/test/functional/p2p_handshake.py
+++ b/test/functional/p2p_handshake.py
@@ -17,6 +17,7 @@ from test_framework.messages import (
     NODE_WITNESS,
 )
 from test_framework.p2p import P2PInterface
+from test_framework.util import p2p_port
 
 
 # Desirable service flags for outbound non-pruned and pruned peers. Note that
@@ -88,9 +89,11 @@ class P2PHandshakeTest(BitcoinTestFramework):
         with node.assert_debug_log([f"feeler connection completed"]):
             self.add_outbound_connection(node, "feeler", NODE_NONE, wait_for_disconnect=True)
 
-        # TODO: re-add test introduced in commit 5d2fb14bafe4e80c0a482d99e5ebde07c477f000
-        # ("test: p2p: check that connecting to ourself leads to disconnect") once
-        # the race condition causing issue #30368 is fixed
+        self.log.info("Check that connecting to ourself leads to immediate disconnect")
+        with node.assert_debug_log(["connected to self", "disconnecting"]):
+            node_listen_addr = f"127.0.0.1:{p2p_port(0)}"
+            node.addconnection(node_listen_addr, "outbound-full-relay", self.options.v2transport)
+            self.wait_until(lambda: len(node.getpeerinfo()) == 0)
 
 
 if __name__ == '__main__':