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Diffstat (limited to 'python/qemu/qmp')
| -rw-r--r-- | python/qemu/qmp/__init__.py | 385 |
1 files changed, 385 insertions, 0 deletions
diff --git a/python/qemu/qmp/__init__.py b/python/qemu/qmp/__init__.py new file mode 100644 index 0000000000..9606248a3d --- /dev/null +++ b/python/qemu/qmp/__init__.py @@ -0,0 +1,385 @@ +""" +QEMU Monitor Protocol (QMP) development library & tooling. + +This package provides a fairly low-level class for communicating to QMP +protocol servers, as implemented by QEMU, the QEMU Guest Agent, and the +QEMU Storage Daemon. This library is not intended for production use. + +`QEMUMonitorProtocol` is the primary class of interest, and all errors +raised derive from `QMPError`. +""" + +# Copyright (C) 2009, 2010 Red Hat Inc. +# +# Authors: +# Luiz Capitulino <lcapitulino@redhat.com> +# +# This work is licensed under the terms of the GNU GPL, version 2. See +# the COPYING file in the top-level directory. + +import errno +import json +import logging +import socket +from types import TracebackType +from typing import ( + Any, + Dict, + List, + Optional, + TextIO, + Tuple, + Type, + Union, + cast, +) + + +# QMPMessage is a QMP Message of any kind. +# e.g. {'yee': 'haw'} +# +# QMPReturnValue is the inner value of return values only. +# {'return': {}} is the QMPMessage, +# {} is the QMPReturnValue. +QMPMessage = Dict[str, Any] +QMPReturnValue = Dict[str, Any] + +InternetAddrT = Tuple[str, str] +UnixAddrT = str +SocketAddrT = Union[InternetAddrT, UnixAddrT] + + +class QMPError(Exception): + """ + QMP base exception + """ + + +class QMPConnectError(QMPError): + """ + QMP connection exception + """ + + +class QMPCapabilitiesError(QMPError): + """ + QMP negotiate capabilities exception + """ + + +class QMPTimeoutError(QMPError): + """ + QMP timeout exception + """ + + +class QMPProtocolError(QMPError): + """ + QMP protocol error; unexpected response + """ + + +class QMPResponseError(QMPError): + """ + Represents erroneous QMP monitor reply + """ + def __init__(self, reply: QMPMessage): + try: + desc = reply['error']['desc'] + except KeyError: + desc = reply + super().__init__(desc) + self.reply = reply + + +class QEMUMonitorProtocol: + """ + Provide an API to connect to QEMU via QEMU Monitor Protocol (QMP) and then + allow to handle commands and events. + """ + + #: Logger object for debugging messages + logger = logging.getLogger('QMP') + + def __init__(self, address: SocketAddrT, + server: bool = False, + nickname: Optional[str] = None): + """ + Create a QEMUMonitorProtocol class. + + @param address: QEMU address, can be either a unix socket path (string) + or a tuple in the form ( address, port ) for a TCP + connection + @param server: server mode listens on the socket (bool) + @raise OSError on socket connection errors + @note No connection is established, this is done by the connect() or + accept() methods + """ + self.__events: List[QMPMessage] = [] + self.__address = address + self.__sock = self.__get_sock() + self.__sockfile: Optional[TextIO] = None + self._nickname = nickname + if self._nickname: + self.logger = logging.getLogger('QMP').getChild(self._nickname) + if server: + self.__sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) + self.__sock.bind(self.__address) + self.__sock.listen(1) + + def __get_sock(self) -> socket.socket: + if isinstance(self.__address, tuple): + family = socket.AF_INET + else: + family = socket.AF_UNIX + return socket.socket(family, socket.SOCK_STREAM) + + def __negotiate_capabilities(self) -> QMPMessage: + greeting = self.__json_read() + if greeting is None or "QMP" not in greeting: + raise QMPConnectError + # Greeting seems ok, negotiate capabilities + resp = self.cmd('qmp_capabilities') + if resp and "return" in resp: + return greeting + raise QMPCapabilitiesError + + def __json_read(self, only_event: bool = False) -> Optional[QMPMessage]: + assert self.__sockfile is not None + while True: + data = self.__sockfile.readline() + if not data: + return None + # By definition, any JSON received from QMP is a QMPMessage, + # and we are asserting only at static analysis time that it + # has a particular shape. + resp: QMPMessage = json.loads(data) + if 'event' in resp: + self.logger.debug("<<< %s", resp) + self.__events.append(resp) + if not only_event: + continue + return resp + + def __get_events(self, wait: Union[bool, float] = False) -> None: + """ + Check for new events in the stream and cache them in __events. + + @param wait (bool): block until an event is available. + @param wait (float): If wait is a float, treat it as a timeout value. + + @raise QMPTimeoutError: If a timeout float is provided and the timeout + period elapses. + @raise QMPConnectError: If wait is True but no events could be + retrieved or if some other error occurred. + """ + + # Current timeout and blocking status + current_timeout = self.__sock.gettimeout() + + # Check for new events regardless and pull them into the cache: + self.__sock.settimeout(0) # i.e. setblocking(False) + try: + self.__json_read() + except OSError as err: + # EAGAIN: No data available; not critical + if err.errno != errno.EAGAIN: + raise + finally: + self.__sock.settimeout(current_timeout) + + # Wait for new events, if needed. + # if wait is 0.0, this means "no wait" and is also implicitly false. + if not self.__events and wait: + if isinstance(wait, float): + self.__sock.settimeout(wait) + try: + ret = self.__json_read(only_event=True) + except socket.timeout as err: + raise QMPTimeoutError("Timeout waiting for event") from err + except Exception as err: + msg = "Error while reading from socket" + raise QMPConnectError(msg) from err + finally: + self.__sock.settimeout(current_timeout) + + if ret is None: + raise QMPConnectError("Error while reading from socket") + + def __enter__(self) -> 'QEMUMonitorProtocol': + # Implement context manager enter function. + return self + + def __exit__(self, + # pylint: disable=duplicate-code + # see https://github.com/PyCQA/pylint/issues/3619 + exc_type: Optional[Type[BaseException]], + exc_val: Optional[BaseException], + exc_tb: Optional[TracebackType]) -> None: + # Implement context manager exit function. + self.close() + + def connect(self, negotiate: bool = True) -> Optional[QMPMessage]: + """ + Connect to the QMP Monitor and perform capabilities negotiation. + + @return QMP greeting dict, or None if negotiate is false + @raise OSError on socket connection errors + @raise QMPConnectError if the greeting is not received + @raise QMPCapabilitiesError if fails to negotiate capabilities + """ + self.__sock.connect(self.__address) + self.__sockfile = self.__sock.makefile(mode='r') + if negotiate: + return self.__negotiate_capabilities() + return None + + def accept(self, timeout: Optional[float] = 15.0) -> QMPMessage: + """ + Await connection from QMP Monitor and perform capabilities negotiation. + + @param timeout: timeout in seconds (nonnegative float number, or + None). The value passed will set the behavior of the + underneath QMP socket as described in [1]. + Default value is set to 15.0. + @return QMP greeting dict + @raise OSError on socket connection errors + @raise QMPConnectError if the greeting is not received + @raise QMPCapabilitiesError if fails to negotiate capabilities + + [1] + https://docs.python.org/3/library/socket.html#socket.socket.settimeout + """ + self.__sock.settimeout(timeout) + self.__sock, _ = self.__sock.accept() + self.__sockfile = self.__sock.makefile(mode='r') + return self.__negotiate_capabilities() + + def cmd_obj(self, qmp_cmd: QMPMessage) -> QMPMessage: + """ + Send a QMP command to the QMP Monitor. + + @param qmp_cmd: QMP command to be sent as a Python dict + @return QMP response as a Python dict + """ + self.logger.debug(">>> %s", qmp_cmd) + self.__sock.sendall(json.dumps(qmp_cmd).encode('utf-8')) + resp = self.__json_read() + if resp is None: + raise QMPConnectError("Unexpected empty reply from server") + self.logger.debug("<<< %s", resp) + return resp + + def cmd(self, name: str, + args: Optional[Dict[str, Any]] = None, + cmd_id: Optional[Any] = None) -> QMPMessage: + """ + Build a QMP command and send it to the QMP Monitor. + + @param name: command name (string) + @param args: command arguments (dict) + @param cmd_id: command id (dict, list, string or int) + """ + qmp_cmd: QMPMessage = {'execute': name} + if args: + qmp_cmd['arguments'] = args + if cmd_id: + qmp_cmd['id'] = cmd_id + return self.cmd_obj(qmp_cmd) + + def command(self, cmd: str, **kwds: Any) -> QMPReturnValue: + """ + Build and send a QMP command to the monitor, report errors if any + """ + ret = self.cmd(cmd, kwds) + if 'error' in ret: + raise QMPResponseError(ret) + if 'return' not in ret: + raise QMPProtocolError( + "'return' key not found in QMP response '{}'".format(str(ret)) + ) + return cast(QMPReturnValue, ret['return']) + + def pull_event(self, + wait: Union[bool, float] = False) -> Optional[QMPMessage]: + """ + Pulls a single event. + + @param wait (bool): block until an event is available. + @param wait (float): If wait is a float, treat it as a timeout value. + + @raise QMPTimeoutError: If a timeout float is provided and the timeout + period elapses. + @raise QMPConnectError: If wait is True but no events could be + retrieved or if some other error occurred. + + @return The first available QMP event, or None. + """ + self.__get_events(wait) + + if self.__events: + return self.__events.pop(0) + return None + + def get_events(self, wait: bool = False) -> List[QMPMessage]: + """ + Get a list of available QMP events. + + @param wait (bool): block until an event is available. + @param wait (float): If wait is a float, treat it as a timeout value. + + @raise QMPTimeoutError: If a timeout float is provided and the timeout + period elapses. + @raise QMPConnectError: If wait is True but no events could be + retrieved or if some other error occurred. + + @return The list of available QMP events. + """ + self.__get_events(wait) + return self.__events + + def clear_events(self) -> None: + """ + Clear current list of pending events. + """ + self.__events = [] + + def close(self) -> None: + """ + Close the socket and socket file. + """ + if self.__sock: + self.__sock.close() + if self.__sockfile: + self.__sockfile.close() + + def settimeout(self, timeout: Optional[float]) -> None: + """ + Set the socket timeout. + + @param timeout (float): timeout in seconds (non-zero), or None. + @note This is a wrap around socket.settimeout + + @raise ValueError: if timeout was set to 0. + """ + if timeout == 0: + msg = "timeout cannot be 0; this engages non-blocking mode." + msg += " Use 'None' instead to disable timeouts." + raise ValueError(msg) + self.__sock.settimeout(timeout) + + def get_sock_fd(self) -> int: + """ + Get the socket file descriptor. + + @return The file descriptor number. + """ + return self.__sock.fileno() + + def is_scm_available(self) -> bool: + """ + Check if the socket allows for SCM_RIGHTS. + + @return True if SCM_RIGHTS is available, otherwise False. + """ + return self.__sock.family == socket.AF_UNIX |