Reapply "test: p2p: check that connecting to ourself leads to disconnect"

This reverts commit 9ec2c53701a391629b55aeb2804e8060d2c453a4 with
a tiny change included (identation of the wait_until call).

Github-Pull: #30394
Rebased-From: 16bd283b3ad05daa41259a062aee0fc05b463fa6

test/functional/p2p_handshake.py

@@ -0,0 +1,26 @@
+#!/usr/bin/env python3
+# Copyright (c) 2024 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""
+Test P2P behaviour during the handshake phase.
+"""
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import p2p_port
+
+
+class P2PHandshakeTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.num_nodes = 1
+
+    def run_test(self):
+        node = self.nodes[0]
+        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__':
+    P2PHandshakeTest().main()

test/functional/test_runner.py

@@ -395,6 +395,8 @@ BASE_SCRIPTS = [
     'rpc_getdescriptorinfo.py',
     'rpc_mempool_info.py',
     'rpc_help.py',
+    'p2p_handshake.py',
+    'p2p_handshake.py --v2transport',
     'feature_dirsymlinks.py',
     'feature_help.py',
     'feature_shutdown.py',