Merge bitcoin/bitcoin#34158: torcontrol: Remove libevent usage

1401011f71 test: Add test for exceeding max line length in torcontrol (Fabian Jahr)
84c1f32071 test: Add torcontrol coverage for PoW defense enablement (Fabian Jahr)
7dff9ec298 test: Add test for partial message handling in torcontrol (Fabian Jahr)
569383356e test: Add simple functional test for torcontrol (Fabian Jahr)
4117b92e67 fuzz: Improve torcontrol fuzz test (Fabian Jahr)
b1869e9a2d torcontrol: Move tor controller into node context (Fabian Jahr)
eae193e750 torcontrol: Remove libevent usage (Fabian Jahr)
8444efbd4a refactor: Get rid of unnecessary newlines in logs (Fabian Jahr)
6bcb60354e refactor: Modernize member variable names in torcontrol (Fabian Jahr)
a36591d194 refactor: Use constexpr in torcontrol where possible (Fabian Jahr)

Pull request description:

  This is part of the effort to remove the libevent dependency from our code base: https://github.com/bitcoin/bitcoin/issues/31194

  The current approach tries to reuse existing code and follows roughly similar design decisions. It replaces the libevent-based async I/O with blocking I/O utilizing the existing `Sock` and `CThreadInterrupt`. The controller runs in a dedicated thread.

  There are some optional code modernizations thrown in made along the way (namings, constexpr etc.). These are not strictly necessary but make the end result with the new code more consistent.

ACKs for top commit:
  achow101:
    ACK 1401011f71
  janb84:
    re ACK 1401011f71
  pinheadmz:
    ACK 1401011f71

Tree-SHA512: 167f1d98a634524568cb1d723e7bdb7234bade2c5686586caf2accea58c3308f83a32e0705edc570d6db691ae578a91e474ae4773f126ec2e1619d3adf7df622

test/functional/feature_torcontrol.py

@@ -0,0 +1,233 @@
+#!/usr/bin/env python3
+# Copyright (c) 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 torcontrol functionality with a mock Tor control server."""
+import socket
+import threading
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import (
+    assert_equal,
+    ensure_for,
+    p2p_port,
+)
+
+
+class MockTorControlServer:
+    def __init__(self, port, manual_mode=False):
+        self.port = port
+        self.sock = None
+        self.conn = None
+        self.running = False
+        self.thread = None
+        self.received_commands = []
+        self.manual_mode = manual_mode
+        self.conn_ready = threading.Event()
+
+    def start(self):
+        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        self.sock.settimeout(1.0)
+        self.sock.bind(('127.0.0.1', self.port))
+        self.sock.listen(1)
+        self.running = True
+        self.thread = threading.Thread(target=self._serve)
+        self.thread.daemon = True
+        self.thread.start()
+
+    def stop(self):
+        self.running = False
+        if self.conn:
+            self.conn.close()
+        if self.sock:
+            self.sock.close()
+        if self.thread:
+            self.thread.join(timeout=5)
+
+    def _serve(self):
+        while self.running:
+            try:
+                self.conn, _ = self.sock.accept()
+                self.conn.settimeout(1.0)
+                self.conn_ready.set()
+                self._handle_connection(self.conn)
+            except socket.timeout:
+                continue
+            except OSError:
+                break
+
+    def _handle_connection(self, conn):
+        try:
+            buf = b""
+            while self.running:
+                try:
+                    data = conn.recv(1024)
+                    if not data:
+                        break
+                    buf += data
+                    while b"\r\n" in buf:
+                        line, buf = buf.split(b"\r\n", 1)
+                        command = line.decode('utf-8').strip()
+                        if command:
+                            self.received_commands.append(command)
+                            if not self.manual_mode:
+                                response = self._get_response(command)
+                                conn.sendall(response.encode('utf-8'))
+                except socket.timeout:
+                    continue
+        finally:
+            conn.close()
+
+    def send_raw(self, data):
+        if self.conn:
+            self.conn.sendall(data.encode('utf-8'))
+
+    def _get_response(self, command):
+        if command == "PROTOCOLINFO 1":
+            return (
+                "250-PROTOCOLINFO 1\r\n"
+                "250-AUTH METHODS=NULL\r\n"
+                "250-VERSION Tor=\"0.1.2.3\"\r\n"
+                "250 OK\r\n"
+            )
+        elif command == "AUTHENTICATE":
+            return "250 OK\r\n"
+        elif command.startswith("ADD_ONION"):
+            return (
+                "250-ServiceID=testserviceid1234567890123456789012345678901234567890123456\r\n"
+                "250 OK\r\n"
+            )
+        elif command.startswith("GETINFO"):
+            return "250-net/listeners/socks=\"127.0.0.1:9050\"\r\n250 OK\r\n"
+        else:
+            return "510 Unrecognized command\r\n"
+
+
+class TorControlTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.num_nodes = 1
+
+    def next_port(self):
+        self._port_counter = getattr(self, '_port_counter', 0) + 1
+        return p2p_port(self.num_nodes + self._port_counter)
+
+    def restart_with_mock(self, mock_tor):
+        mock_tor.start()
+        self.restart_node(0, extra_args=[
+            f"-torcontrol=127.0.0.1:{mock_tor.port}",
+            "-listenonion=1",
+            "-debug=tor",
+        ])
+
+    def test_basic(self):
+        self.log.info("Test Tor control basic functionality")
+
+        mock_tor = MockTorControlServer(self.next_port())
+        self.restart_with_mock(mock_tor)
+
+        # Waiting for Tor control commands
+        self.wait_until(lambda: len(mock_tor.received_commands) >= 4, timeout=10)
+
+        # Verify expected protocol sequence
+        assert_equal(mock_tor.received_commands[0], "PROTOCOLINFO 1")
+        assert_equal(mock_tor.received_commands[1], "AUTHENTICATE")
+        assert_equal(mock_tor.received_commands[2], "GETINFO net/listeners/socks")
+        assert mock_tor.received_commands[3].startswith("ADD_ONION ")
+        assert "PoWDefensesEnabled=1" in mock_tor.received_commands[3]
+
+        # Clean up
+        mock_tor.stop()
+
+    def test_partial_data(self):
+        self.log.info("Test that partial Tor control responses are buffered until complete")
+
+        mock_tor = MockTorControlServer(self.next_port(), manual_mode=True)
+        self.restart_with_mock(mock_tor)
+
+        # Wait for connection and PROTOCOLINFO command
+        mock_tor.conn_ready.wait(timeout=10)
+        self.wait_until(lambda: len(mock_tor.received_commands) >= 1, timeout=10)
+        assert_equal(mock_tor.received_commands[0], "PROTOCOLINFO 1")
+
+        # Send partial response (no \r\n on last line)
+        mock_tor.send_raw(
+            "250-PROTOCOLINFO 1\r\n"
+            "250-AUTH METHODS=NULL\r\n"
+            "250 OK"
+        )
+
+        # Verify AUTHENTICATE is not sent
+        ensure_for(duration=2, f=lambda: len(mock_tor.received_commands) == 1)
+
+        # Complete the response
+        mock_tor.send_raw("\r\n")
+
+        # Should now process the complete response and send AUTHENTICATE
+        self.wait_until(lambda: len(mock_tor.received_commands) >= 2, timeout=5)
+        assert_equal(mock_tor.received_commands[1], "AUTHENTICATE")
+
+        # Clean up
+        mock_tor.stop()
+
+    def test_pow_fallback(self):
+        self.log.info("Test that ADD_ONION retries without PoW on 512 error")
+
+        class NoPowServer(MockTorControlServer):
+            def _get_response(self, command):
+                if command.startswith("ADD_ONION"):
+                    if "PoWDefensesEnabled=1" in command:
+                        return "512 Unrecognized option\r\n"
+                    else:
+                        return (
+                            "250-ServiceID=testserviceid1234567890123456789012345678901234567890123456\r\n"
+                            "250 OK\r\n"
+                        )
+                return super()._get_response(command)
+
+        mock_tor = NoPowServer(self.next_port())
+        self.restart_with_mock(mock_tor)
+
+        # Expect: PROTOCOLINFO, AUTHENTICATE, GETINFO, ADD_ONION (with PoW), ADD_ONION (without PoW)
+        self.wait_until(lambda: len(mock_tor.received_commands) >= 5, timeout=10)
+
+        # First ADD_ONION should have PoW enabled
+        assert mock_tor.received_commands[3].startswith("ADD_ONION ")
+        assert "PoWDefensesEnabled=1" in mock_tor.received_commands[3]
+
+        # Retry should be ADD_ONION without PoW
+        assert mock_tor.received_commands[4].startswith("ADD_ONION ")
+        assert "PoWDefensesEnabled=1" not in mock_tor.received_commands[4]
+
+        # Clean up
+        mock_tor.stop()
+
+    def test_oversized_line(self):
+        self.log.info("Test that Tor control disconnects on oversized response lines")
+
+        mock_tor = MockTorControlServer(self.next_port(), manual_mode=True)
+        self.restart_with_mock(mock_tor)
+
+        # Wait for connection and PROTOCOLINFO command.
+        mock_tor.conn_ready.wait(timeout=10)
+        self.wait_until(lambda: len(mock_tor.received_commands) >= 1, timeout=10)
+        assert_equal(mock_tor.received_commands[0], "PROTOCOLINFO 1")
+
+        # Send a single line longer than MAX_LINE_LENGTH. The node should disconnect.
+        MAX_LINE_LENGTH = 100000
+        mock_tor.send_raw("250-" + ("A" * (MAX_LINE_LENGTH + 1)) + "\r\n")
+        ensure_for(duration=2, f=lambda: self.nodes[0].process.poll() is None)
+
+        # Connection should be dropped and retried, causing another PROTOCOLINFO.
+        self.wait_until(lambda: len(mock_tor.received_commands) >= 2, timeout=10)
+        assert_equal(mock_tor.received_commands[1], "PROTOCOLINFO 1")
+
+        mock_tor.stop()
+
+    def run_test(self):
+        self.test_basic()
+        self.test_partial_data()
+        self.test_pow_fallback()
+        self.test_oversized_line()
+
+if __name__ == '__main__':
+    TorControlTest(__file__).main()

test/functional/test_runner.py

@@ -352,6 +352,7 @@ BASE_SCRIPTS = [
     'tool_bitcoin.py',
     'p2p_sendtxrcncl.py',
     'rpc_scantxoutset.py',
+    'feature_torcontrol.py',
     'feature_unsupported_utxo_db.py',
     'mempool_cluster.py',
     'feature_logging.py',