fix: an answer whose client went away ends quietly, and a shell whose client left before it opened is stopped.

debian-package/src/usr/lib/vpn-router/vpnrouter_web/shell.py

@@ -367,11 +367,14 @@ def shell(handler, name):
     def refuse(code, message):
         log(f'shell of {name} from {handler.client()} refused: {message}')
         body = json.dumps({'error': message}).encode() + b'\n'
-        handler.send_response(code)
-        handler.send_header('Content-Type', 'application/json')
-        handler.send_header('Content-Length', str(len(body)))
-        handler.end_headers()
-        handler.wfile.write(body)
+        try:
+            handler.send_response(code)
+            handler.send_header('Content-Type', 'application/json')
+            handler.send_header('Content-Length', str(len(body)))
+            handler.end_headers()
+            handler.wfile.write(body)
+        except ConnectionError:
+            handler.close_connection = True
 
     key = handler.headers.get('Sec-WebSocket-Key', '').strip()
     if handler.headers.get('Upgrade', '').lower() != 'websocket' or 'upgrade' not in handler.headers.get('Connection', '').lower() \
@@ -408,12 +411,21 @@ def shell(handler, name):
     finally:
         os.close(terminal)
     accept = base64.b64encode(hashlib.sha1((key + WEBSOCKET_GUID).encode()).digest()).decode()
-    handler.send_response(101, 'Switching Protocols')
-    handler.send_header('Upgrade', 'websocket')
-    handler.send_header('Connection', 'Upgrade')
-    handler.send_header('Sec-WebSocket-Accept', accept)
-    handler.end_headers()
     handler.close_connection = True
+    try:
+        handler.send_response(101, 'Switching Protocols')
+        handler.send_header('Upgrade', 'websocket')
+        handler.send_header('Connection', 'Upgrade')
+        handler.send_header('Sec-WebSocket-Accept', accept)
+        handler.end_headers()
+    except ConnectionError:
+        # The client went away before the shell opened; the shell started for it is stopped.
+        run('systemctl', 'stop', unit)
+        os.close(master)
+        process.kill()
+        process.wait()
+        log(f'shell of {name} from {handler.client()} ended before it opened: the client closed the connection')
+        return
     client, started, idle = handler.client(), time.monotonic(), options['shell_idle_minutes'] * 60
     log(f'shell of {name} from {client} opened as {account.pw_name} in {unit}')