From 1219fd08ca36aa85fb5a0c230b7d127aff972666 Mon Sep 17 00:00:00 2001
From: Brian Warner <warner@lothar.com>
Date: Sun, 11 Aug 2019 18:47:54 -0700
Subject: [PATCH] subchannel: enforce separation between half-close and
 full-close API

---
 src/wormhole/_dilation/subchannel.py        | 16 ++++++++++++++++
 src/wormhole/test/dilate/test_subchannel.py | 15 +++++++++++----
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/src/wormhole/_dilation/subchannel.py b/src/wormhole/_dilation/subchannel.py
index 1e52e90..cca0d3c 100644
--- a/src/wormhole/_dilation/subchannel.py
+++ b/src/wormhole/_dilation/subchannel.py
@@ -56,6 +56,11 @@ class SingleUseEndpointError(Exception):
 class AlreadyClosedError(Exception):
     pass
 
+class NormalCloseUsedOnHalfCloseable(Exception):
+    pass
+class HalfCloseUsedOnNonHalfCloseable(Exception):
+    pass
+
 
 @implementer(IAddress)
 class _WormholeAddress(object):
@@ -265,7 +270,18 @@ class SubChannel(object):
     def writeSequence(self, iovec):
         self.write(b"".join(iovec))
 
+    def loseWriteConnection(self):
+        if not IHalfCloseableProtocol.providedBy(self._protocol):
+            # this is a clear error
+            raise HalfCloseUsedOnNonHalfCloseable()
+        self.local_close();
+
     def loseConnection(self):
+        # TODO: what happens if an IHalfCloseableProtocol calls normal
+        # loseConnection()? I think we need to close the read side too.
+        if IHalfCloseableProtocol.providedBy(self._protocol):
+            # I don't know is correct, so avoid this for now
+            raise NormalCloseUsedOnHalfCloseable()
         self.local_close()
 
     def getHost(self):
diff --git a/src/wormhole/test/dilate/test_subchannel.py b/src/wormhole/test/dilate/test_subchannel.py
index 45d4d98..88e6565 100644
--- a/src/wormhole/test/dilate/test_subchannel.py
+++ b/src/wormhole/test/dilate/test_subchannel.py
@@ -6,7 +6,8 @@ from twisted.internet.interfaces import ITransport, IHalfCloseableProtocol
 from twisted.internet.error import ConnectionDone
 from ..._dilation.subchannel import (Once, SubChannel,
                                      _WormholeAddress, _SubchannelAddress,
-                                     AlreadyClosedError)
+                                     AlreadyClosedError,
+                                     NormalCloseUsedOnHalfCloseable)
 from .common import mock_manager
 
 
@@ -174,9 +175,12 @@ class HalfCloseable(unittest.TestCase):
         self.assertEqual(p.mock_calls, [mock.call.dataReceived(b"inbound1")])
         p.mock_calls[:] = []
 
+        with self.assertRaises(NormalCloseUsedOnHalfCloseable) as e:
+            sc.loseConnection() # TODO: maybe this shouldn't be an error
+
         # after a local close, we can't write anymore, but we can still
         # receive data
-        sc.loseConnection()
+        sc.loseWriteConnection() # TODO or loseConnection?
         self.assertEqual(m.mock_calls, [mock.call.send_close(scid)])
         m.mock_calls[:] = []
         self.assertEqual(p.mock_calls, [mock.call.writeConnectionLost()])
@@ -188,10 +192,13 @@ class HalfCloseable(unittest.TestCase):
                          "write not allowed on closed subchannel")
 
         with self.assertRaises(AlreadyClosedError) as e:
-            sc.loseConnection()
+            sc.loseWriteConnection()
         self.assertEqual(str(e.exception),
                          "loseConnection not allowed on closed subchannel")
 
+        with self.assertRaises(NormalCloseUsedOnHalfCloseable) as e:
+            sc.loseConnection() # TODO: maybe expect AlreadyClosedError
+
         sc.remote_data(b"inbound2")
         self.assertEqual(p.mock_calls, [mock.call.dataReceived(b"inbound2")])
         p.mock_calls[:] = []
@@ -223,7 +230,7 @@ class HalfCloseable(unittest.TestCase):
         m.mock_calls[:] = []
 
         # and a local close will shutdown the connection
-        sc.loseConnection()
+        sc.loseWriteConnection()
         self.assertEqual(m.mock_calls, [mock.call.send_close(scid),
                                         mock.call.subchannel_closed(scid, sc)])
         self.assertEqual(p.mock_calls, [mock.call.writeConnectionLost()])