StreamInterface: prevent socket/reader-thread leak on handshake failure in __init__

If connect() or waitForConfig() raises during __init__ (handshake timeout,
bad stream, config error), the reader thread started by connect() keeps
running and the underlying stream/socket stays open — but the caller never
receives a reference to the half-initialized instance, so they cannot call
close() themselves. The leak compounds on every retry from a caller's
reconnect loop.

Fix: wrap connect() + waitForConfig() in try/except; call self.close() on
any exception before re-raising. Also guard close() against RuntimeError
from joining an unstarted reader thread (happens when close() runs from
a failed __init__ before connect() could spawn it).

Discovered while debugging a real-world Meshtastic firmware crash where
a passive logger's retrying TCPInterface() calls against a node with
250-entry NodeDB produced a reconnect storm — every retry triggered a
full config+NodeDB dump on the node, compounding heap pressure, which
then exposed null-deref bugs in Router::perhapsDecode / MeshService
(firmware side fixed in meshtastic/firmware#10226 and #10229). The
client-side leak is independent of those firmware bugs and worth fixing
on its own.

Author: nightjoker7

meshtastic/stream_interface.py

@@ -1,5 +1,6 @@
 """Stream Interface base class
 """
+import contextlib
 import io
 import logging
 import threading
@@ -61,9 +62,17 @@ def __init__( # pylint: disable=R0917
 
         # Start the reader thread after superclass constructor completes init
         if connectNow:
-            self.connect()
-            if not noProto:
-                self.waitForConfig()
+            try:
+                self.connect()
+                if not noProto:
+                    self.waitForConfig()
+            except Exception:
+                # If the handshake raises, the caller never receives a reference
+                # to this instance and cannot call close() themselves. Clean up
+                # the reader thread + stream here so retries don't leak.
+                with contextlib.suppress(Exception):
+                    self.close()
+                raise
 
     def connect(self) -> None:
         """Connect to our radio
@@ -136,7 +145,13 @@ def close(self) -> None:
         # reader thread to close things for us
         self._wantExit = True
         if self._rxThread != threading.current_thread():
-            self._rxThread.join()  # wait for it to exit
+            try:
+                self._rxThread.join()  # wait for it to exit
+            except RuntimeError:
+                # Thread was never started — happens when close() is invoked
+                # from a failed __init__ before connect() could spawn it.
+                # Nothing to join; safe to ignore.
+                pass
 
     def _handleLogByte(self, b):
         """Handle a byte that is part of a log message from the device."""

meshtastic/tests/test_stream_interface.py

@@ -18,6 +18,101 @@ def test_StreamInterface():
     assert pytest_wrapped_e.type == Exception
 
 
+@pytest.mark.unit
+@pytest.mark.usefixtures("reset_mt_config")
+def test_StreamInterface_close_safe_when_thread_never_started():
+    """close() must not raise RuntimeError when called before connect() has started the reader.
+
+    Hits the cleanup path used by __init__ when the handshake raises before the
+    reader thread is started.
+    """
+    iface = StreamInterface(noProto=True, connectNow=False)
+    iface.stream = MagicMock()
+    # _rxThread was created in __init__ but never .start()'d. close() should
+    # detect that and skip join() instead of raising RuntimeError.
+    iface.close()
+
+
+@pytest.mark.unit
+@pytest.mark.usefixtures("reset_mt_config")
+def test_StreamInterface_init_cleans_up_when_connect_raises():
+    """If connect() raises during __init__, close() runs and the original exception propagates."""
+
+    cleanup_calls = []
+
+    class FailingConnectStream(StreamInterface):
+        """Subclass whose connect() raises, to exercise the __init__ cleanup path."""
+
+        def __init__(self):
+            self.stream = MagicMock()  # bypass StreamInterface abstract check
+            super().__init__(noProto=False, connectNow=True)
+
+        def connect(self):
+            raise RuntimeError("simulated handshake failure")
+
+        def close(self):
+            cleanup_calls.append("close")
+            super().close()
+
+    with pytest.raises(RuntimeError, match="simulated handshake failure"):
+        FailingConnectStream()
+    assert cleanup_calls == ["close"], "close() should be invoked exactly once on handshake failure"
+
+
+@pytest.mark.unit
+@pytest.mark.usefixtures("reset_mt_config")
+def test_StreamInterface_init_cleans_up_when_waitForConfig_raises():
+    """If waitForConfig() raises after a successful connect(), close() runs and exception propagates."""
+
+    cleanup_calls = []
+
+    class FailingWaitStream(StreamInterface):
+        """Subclass whose waitForConfig() raises, to exercise the second leg of cleanup."""
+
+        def __init__(self):
+            self.stream = MagicMock()
+            super().__init__(noProto=False, connectNow=True)
+
+        def connect(self):
+            # No-op connect — we are simulating handshake-stage failure, not connect-stage.
+            pass
+
+        def waitForConfig(self):
+            raise TimeoutError("simulated config-handshake timeout")
+
+        def close(self):
+            cleanup_calls.append("close")
+            super().close()
+
+    with pytest.raises(TimeoutError, match="simulated config-handshake timeout"):
+        FailingWaitStream()
+    assert cleanup_calls == ["close"], "close() should be invoked exactly once on handshake timeout"
+
+
+@pytest.mark.unit
+@pytest.mark.usefixtures("reset_mt_config")
+def test_StreamInterface_init_cleanup_does_not_shadow_original_exception():
+    """If close() itself raises during __init__ cleanup, the original exception still propagates.
+
+    The cleanup uses contextlib.suppress(Exception) so that a secondary failure
+    in close() doesn't replace the real reason for the failed handshake.
+    """
+
+    class CleanupRaisesStream(StreamInterface):
+        def __init__(self):
+            self.stream = MagicMock()
+            super().__init__(noProto=False, connectNow=True)
+
+        def connect(self):
+            raise RuntimeError("original handshake failure")
+
+        def close(self):
+            raise RuntimeError("secondary close failure — should be suppressed")
+
+    with pytest.raises(RuntimeError, match="original handshake failure"):
+        CleanupRaisesStream()
+
+
 # Note: This takes a bit, so moving from unit to slow
 @pytest.mark.unitslow
 @pytest.mark.usefixtures("reset_mt_config")