python/qemu/qmp.py

   1 """ QEMU Monitor Protocol Python class """
   2 # Copyright (C) 2009, 2010 Red Hat Inc.
   3 #
   4 # Authors:
   5 #  Luiz Capitulino <lcapitulino@redhat.com>
   6 #
   7 # This work is licensed under the terms of the GNU GPL, version 2.  See
   8 # the COPYING file in the top-level directory.
   9
  10 import errno
  11 import json
  12 import logging
  13 import socket
  14 from types import TracebackType
  15 from typing import (
  16     Any,
  17     Dict,
  18     List,
  19     Optional,
  20     TextIO,
  21     Tuple,
  22     Type,
  23     Union,
  24     cast,
  25 )
  26
  27
  28 # QMPMessage is a QMP Message of any kind.
  29 # e.g. {'yee': 'haw'}
  30 #
  31 # QMPReturnValue is the inner value of return values only.
  32 # {'return': {}} is the QMPMessage,
  33 # {} is the QMPReturnValue.
  34 QMPMessage = Dict[str, Any]
  35 QMPReturnValue = Dict[str, Any]
  36
  37 InternetAddrT = Tuple[str, str]
  38 UnixAddrT = str
  39 SocketAddrT = Union[InternetAddrT, UnixAddrT]
  40
  41
  42 class QMPError(Exception):
  43     """
  44     QMP base exception
  45     """
  46
  47
  48 class QMPConnectError(QMPError):
  49     """
  50     QMP connection exception
  51     """
  52
  53
  54 class QMPCapabilitiesError(QMPError):
  55     """
  56     QMP negotiate capabilities exception
  57     """
  58
  59
  60 class QMPTimeoutError(QMPError):
  61     """
  62     QMP timeout exception
  63     """
  64
  65
  66 class QMPProtocolError(QMPError):
  67     """
  68     QMP protocol error; unexpected response
  69     """
  70
  71
  72 class QMPResponseError(QMPError):
  73     """
  74     Represents erroneous QMP monitor reply
  75     """
  76     def __init__(self, reply: QMPMessage):
  77         try:
  78             desc = reply['error']['desc']
  79         except KeyError:
  80             desc = reply
  81         super().__init__(desc)
  82         self.reply = reply
  83
  84
  85 class QEMUMonitorProtocol:
  86     """
  87     Provide an API to connect to QEMU via QEMU Monitor Protocol (QMP) and then
  88     allow to handle commands and events.
  89     """
  90
  91     #: Logger object for debugging messages
  92     logger = logging.getLogger('QMP')
  93
  94     def __init__(self, address: SocketAddrT,
  95                  server: bool = False,
  96                  nickname: Optional[str] = None):
  97         """
  98         Create a QEMUMonitorProtocol class.
  99
 100         @param address: QEMU address, can be either a unix socket path (string)
 101                         or a tuple in the form ( address, port ) for a TCP
 102                         connection
 103         @param server: server mode listens on the socket (bool)
 104         @raise OSError on socket connection errors
 105         @note No connection is established, this is done by the connect() or
 106               accept() methods
 107         """
 108         self.__events: List[QMPMessage] = []
 109         self.__address = address
 110         self.__sock = self.__get_sock()
 111         self.__sockfile: Optional[TextIO] = None
 112         self._nickname = nickname
 113         if self._nickname:
 114             self.logger = logging.getLogger('QMP').getChild(self._nickname)
 115         if server:
 116             self.__sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
 117             self.__sock.bind(self.__address)
 118             self.__sock.listen(1)
 119
 120     def __get_sock(self) -> socket.socket:
 121         if isinstance(self.__address, tuple):
 122             family = socket.AF_INET
 123         else:
 124             family = socket.AF_UNIX
 125         return socket.socket(family, socket.SOCK_STREAM)
 126
 127     def __negotiate_capabilities(self) -> QMPMessage:
 128         greeting = self.__json_read()
 129         if greeting is None or "QMP" not in greeting:
 130             raise QMPConnectError
 131         # Greeting seems ok, negotiate capabilities
 132         resp = self.cmd('qmp_capabilities')
 133         if resp and "return" in resp:
 134             return greeting
 135         raise QMPCapabilitiesError
 136
 137     def __json_read(self, only_event: bool = False) -> Optional[QMPMessage]:
 138         assert self.__sockfile is not None
 139         while True:
 140             data = self.__sockfile.readline()
 141             if not data:
 142                 return None
 143             # By definition, any JSON received from QMP is a QMPMessage,
 144             # and we are asserting only at static analysis time that it
 145             # has a particular shape.
 146             resp: QMPMessage = json.loads(data)
 147             if 'event' in resp:
 148                 self.logger.debug("<<< %s", resp)
 149                 self.__events.append(resp)
 150                 if not only_event:
 151                     continue
 152             return resp
 153
 154     def __get_events(self, wait: Union[bool, float] = False) -> None:
 155         """
 156         Check for new events in the stream and cache them in __events.
 157
 158         @param wait (bool): block until an event is available.
 159         @param wait (float): If wait is a float, treat it as a timeout value.
 160
 161         @raise QMPTimeoutError: If a timeout float is provided and the timeout
 162                                 period elapses.
 163         @raise QMPConnectError: If wait is True but no events could be
 164                                 retrieved or if some other error occurred.
 165         """
 166
 167         # Check for new events regardless and pull them into the cache:
 168         self.__sock.setblocking(False)
 169         try:
 170             self.__json_read()
 171         except OSError as err:
 172             if err.errno == errno.EAGAIN:
 173                 # No data available
 174                 pass
 175         self.__sock.setblocking(True)
 176
 177         # Wait for new events, if needed.
 178         # if wait is 0.0, this means "no wait" and is also implicitly false.
 179         if not self.__events and wait:
 180             if isinstance(wait, float):
 181                 self.__sock.settimeout(wait)
 182             try:
 183                 ret = self.__json_read(only_event=True)
 184             except socket.timeout:
 185                 raise QMPTimeoutError("Timeout waiting for event")
 186             except:
 187                 raise QMPConnectError("Error while reading from socket")
 188             if ret is None:
 189                 raise QMPConnectError("Error while reading from socket")
 190             self.__sock.settimeout(None)
 191
 192     def __enter__(self) -> 'QEMUMonitorProtocol':
 193         # Implement context manager enter function.
 194         return self
 195
 196     def __exit__(self,
 197                  # pylint: disable=duplicate-code
 198                  # see https://github.com/PyCQA/pylint/issues/3619
 199                  exc_type: Optional[Type[BaseException]],
 200                  exc_val: Optional[BaseException],
 201                  exc_tb: Optional[TracebackType]) -> None:
 202         # Implement context manager exit function.
 203         self.close()
 204
 205     def connect(self, negotiate: bool = True) -> Optional[QMPMessage]:
 206         """
 207         Connect to the QMP Monitor and perform capabilities negotiation.
 208
 209         @return QMP greeting dict, or None if negotiate is false
 210         @raise OSError on socket connection errors
 211         @raise QMPConnectError if the greeting is not received
 212         @raise QMPCapabilitiesError if fails to negotiate capabilities
 213         """
 214         self.__sock.connect(self.__address)
 215         self.__sockfile = self.__sock.makefile(mode='r')
 216         if negotiate:
 217             return self.__negotiate_capabilities()
 218         return None
 219
 220     def accept(self, timeout: float = 15.0) -> QMPMessage:
 221         """
 222         Await connection from QMP Monitor and perform capabilities negotiation.
 223
 224         @param timeout: timeout in seconds (nonnegative float number, or
 225                         None). The value passed will set the behavior of the
 226                         underneath QMP socket as described in [1].
 227                         Default value is set to 15.0.
 228         @return QMP greeting dict
 229         @raise OSError on socket connection errors
 230         @raise QMPConnectError if the greeting is not received
 231         @raise QMPCapabilitiesError if fails to negotiate capabilities
 232
 233         [1]
 234         https://docs.python.org/3/library/socket.html#socket.socket.settimeout
 235         """
 236         self.__sock.settimeout(timeout)
 237         self.__sock, _ = self.__sock.accept()
 238         self.__sockfile = self.__sock.makefile(mode='r')
 239         return self.__negotiate_capabilities()
 240
 241     def cmd_obj(self, qmp_cmd: QMPMessage) -> QMPMessage:
 242         """
 243         Send a QMP command to the QMP Monitor.
 244
 245         @param qmp_cmd: QMP command to be sent as a Python dict
 246         @return QMP response as a Python dict
 247         """
 248         self.logger.debug(">>> %s", qmp_cmd)
 249         self.__sock.sendall(json.dumps(qmp_cmd).encode('utf-8'))
 250         resp = self.__json_read()
 251         if resp is None:
 252             raise QMPConnectError("Unexpected empty reply from server")
 253         self.logger.debug("<<< %s", resp)
 254         return resp
 255
 256     def cmd(self, name: str,
 257             args: Optional[Dict[str, Any]] = None,
 258             cmd_id: Optional[Any] = None) -> QMPMessage:
 259         """
 260         Build a QMP command and send it to the QMP Monitor.
 261
 262         @param name: command name (string)
 263         @param args: command arguments (dict)
 264         @param cmd_id: command id (dict, list, string or int)
 265         """
 266         qmp_cmd: QMPMessage = {'execute': name}
 267         if args:
 268             qmp_cmd['arguments'] = args
 269         if cmd_id:
 270             qmp_cmd['id'] = cmd_id
 271         return self.cmd_obj(qmp_cmd)
 272
 273     def command(self, cmd: str, **kwds: Any) -> QMPReturnValue:
 274         """
 275         Build and send a QMP command to the monitor, report errors if any
 276         """
 277         ret = self.cmd(cmd, kwds)
 278         if 'error' in ret:
 279             raise QMPResponseError(ret)
 280         if 'return' not in ret:
 281             raise QMPProtocolError(
 282                 "'return' key not found in QMP response '{}'".format(str(ret))
 283             )
 284         return cast(QMPReturnValue, ret['return'])
 285
 286     def pull_event(self,
 287                    wait: Union[bool, float] = False) -> Optional[QMPMessage]:
 288         """
 289         Pulls a single event.
 290
 291         @param wait (bool): block until an event is available.
 292         @param wait (float): If wait is a float, treat it as a timeout value.
 293
 294         @raise QMPTimeoutError: If a timeout float is provided and the timeout
 295                                 period elapses.
 296         @raise QMPConnectError: If wait is True but no events could be
 297                                 retrieved or if some other error occurred.
 298
 299         @return The first available QMP event, or None.
 300         """
 301         self.__get_events(wait)
 302
 303         if self.__events:
 304             return self.__events.pop(0)
 305         return None
 306
 307     def get_events(self, wait: bool = False) -> List[QMPMessage]:
 308         """
 309         Get a list of available QMP events.
 310
 311         @param wait (bool): block until an event is available.
 312         @param wait (float): If wait is a float, treat it as a timeout value.
 313
 314         @raise QMPTimeoutError: If a timeout float is provided and the timeout
 315                                 period elapses.
 316         @raise QMPConnectError: If wait is True but no events could be
 317                                 retrieved or if some other error occurred.
 318
 319         @return The list of available QMP events.
 320         """
 321         self.__get_events(wait)
 322         return self.__events
 323
 324     def clear_events(self) -> None:
 325         """
 326         Clear current list of pending events.
 327         """
 328         self.__events = []
 329
 330     def close(self) -> None:
 331         """
 332         Close the socket and socket file.
 333         """
 334         if self.__sock:
 335             self.__sock.close()
 336         if self.__sockfile:
 337             self.__sockfile.close()
 338
 339     def settimeout(self, timeout: float) -> None:
 340         """
 341         Set the socket timeout.
 342
 343         @param timeout (float): timeout in seconds, or None.
 344         @note This is a wrap around socket.settimeout
 345         """
 346         self.__sock.settimeout(timeout)
 347
 348     def get_sock_fd(self) -> int:
 349         """
 350         Get the socket file descriptor.
 351
 352         @return The file descriptor number.
 353         """
 354         return self.__sock.fileno()
 355
 356     def is_scm_available(self) -> bool:
 357         """
 358         Check if the socket allows for SCM_RIGHTS.
 359
 360         @return True if SCM_RIGHTS is available, otherwise False.
 361         """
 362         return self.__sock.family == socket.AF_UNIX