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Libvirt provides QMP passthrough APIs for the QEMU driver and these are exposed in virsh. It is not especially pleasant, however, using the raw QMP JSON syntax. QEMU has a tool 'qmp-shell' which can speak QMP and exposes a human friendly interactive shell. It is not possible to use this with libvirt managed guest, however, since only one client can attach to the QMP socket at any point in time. While it would be possible to configure a second QMP socket for a VM, it may not be an known requirement at the time the guest is provisioned. The virt-qmp-proxy tool aims to solve this problem. It opens a UNIX socket and listens for incoming client connections, speaking QMP on the connected socket. It will forward any QMP commands received onto the running libvirt QEMU guest, and forward any replies back to the QMP client. It will also forward back events. $ virsh start demo $ virt-qmp-proxy demo demo.qmp & $ qmp-shell demo.qmp Welcome to the QMP low-level shell! Connected to QEMU 6.2.0 (QEMU) query-kvm { "return": { "enabled": true, "present": true } } Note this tool of course has the same risks as the raw libvirt QMP passthrough. It is safe to run query commands to fetch information but commands which change the QEMU state risk disrupting libvirt's management of QEMU, potentially resulting in data loss/corruption in the worst case. Any use of this tool will cause the guest to be marked as tainted as an warning that it could be in an unexpected state. Since this tool introduces a python dependency it is not desirable to include it in any of the existing RPMs in libvirt. This tool is also QEMU specific, so isn't appropriate to bundle with the generic tools. Thus a new RPM is introduced 'libvirt-clients-qemu', to contain additional QEMU specific tools, with extra external deps. Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
352 lines
10 KiB
Python
Executable File
352 lines
10 KiB
Python
Executable File
#!/usr/bin/env python3
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import argparse
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import array
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import libvirt
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import libvirt_qemu
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import os
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import re
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import socket
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import sys
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import traceback
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import json
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import fcntl
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debug = False
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def get_domain(uri, domstr):
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conn = libvirt.open(uri)
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dom = None
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saveex = None
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def try_lookup(cb):
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try:
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return cb()
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except libvirt.libvirtError as ex:
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nonlocal saveex
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if saveex is None:
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saveex = ex
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if re.match(r'^\d+$', domstr):
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dom = try_lookup(lambda: conn.lookupByID(int(domstr)))
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if dom is None and re.match(r'^[-a-f0-9]{36}|[a-f0-9]{32}$', domstr):
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dom = try_lookup(lambda: conn.lookupByUUIDString(domstr))
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if dom is None:
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dom = try_lookup(lambda: conn.lookupByName(domstr))
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if dom is None:
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raise saveex
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if not dom.isActive():
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raise Exception("Domain must be running to use QMP")
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return conn, dom
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class QMPProxy(object):
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def __init__(self, conn, dom, serversock, verbose):
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self.conn = conn
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self.dom = dom
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self.verbose = verbose
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self.serversock = serversock
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self.serverwatch = 0
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self.clientsock = None
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self.clientwatch = 0
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self.api2sock = bytes([])
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self.api2sockfds = []
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self.sock2api = bytes([])
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self.sock2apifds = []
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self.serverwatch = libvirt.virEventAddHandle(
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self.serversock.fileno(), libvirt.VIR_EVENT_HANDLE_READABLE,
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self.handle_server_io, self)
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libvirt_qemu.qemuMonitorEventRegister(self.conn, self.dom,
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None,
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self.handle_qmp_event,
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self)
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@staticmethod
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def handle_qmp_event(conn, dom, event, secs, usecs, details, self):
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evdoc = {
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"event": event,
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"timestamp": {"seconds": secs, "microseconds": usecs}
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}
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if details is not None:
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evdoc["data"] = details
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ev = json.dumps(evdoc)
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if self.verbose:
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print(ev)
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ev += "\r\n"
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self.api2sock += ev.encode("utf-8")
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self.update_client_events()
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def recv_with_fds(self):
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# Match VIR_NET_MESSAGE_NUM_FDS_MAX in virnetprotocol.x
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maxfds = 32
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fds = array.array('i')
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cmsgdatalen = socket.CMSG_LEN(maxfds * fds.itemsize)
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data, cmsgdata, flags, addr = self.clientsock.recvmsg(1024,
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cmsgdatalen)
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for cmsg_level, cmsg_type, cmsg_data in cmsgdata:
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scm_rights = (cmsg_level == socket.SOL_SOCKET and
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cmsg_type == socket.SCM_RIGHTS)
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if scm_rights:
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fds.frombytes(cmsg_data[:len(cmsg_data) -
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(len(cmsg_data) % fds.itemsize)])
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else:
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raise Exception("Unexpected CMSGDATA level %d type %d" % (
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cmsg_level, cmsg_type))
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return data, [self.make_file(fd) for fd in fds]
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def send_with_fds(self, data, fds):
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cfds = [fd.fileno() for fd in fds]
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cmsgdata = [(socket.SOL_SOCKET, socket.SCM_RIGHTS,
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array.array("i", cfds))]
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return self.clientsock.sendmsg([data], cmsgdata)
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@staticmethod
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def make_file(fd):
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flags = fcntl.fcntl(fd, fcntl.F_GETFL)
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mask = os.O_RDONLY | os.O_WRONLY | os.O_RDWR | os.O_APPEND
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flags = flags & mask
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mode = ""
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if flags == os.O_RDONLY:
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mode = "rb"
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elif flags == os.O_WRONLY:
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mode = "wb"
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elif flags == os.O_RDWR:
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mode = "r+b"
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elif flags == (os.O_WRONLY | os.O_APPEND):
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mode = "ab"
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elif flags == (os.O_RDWR | os.O_APPEND):
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mode = "a+b"
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return os.fdopen(fd, mode)
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def add_client(self, sock):
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ver = self.conn.getVersion()
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major = int(ver / 1000000) % 1000
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minor = int(ver / 1000) % 1000
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micro = ver % 1000
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greetingobj = {
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"QMP": {
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"version": {
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"qemu": {
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"major": major,
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"minor": minor,
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"micro": micro,
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},
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"package": f"qemu-{major}.{minor}.{micro}",
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},
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"capabilities": [
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"oob"
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],
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}
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}
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greeting = json.dumps(greetingobj)
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if self.verbose:
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print(greeting)
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greeting += "\r\n"
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self.clientsock = sock
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self.clientwatch = libvirt.virEventAddHandle(
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self.clientsock.fileno(), libvirt.VIR_EVENT_HANDLE_WRITABLE,
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self.handle_client_io, self)
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self.api2sock += greeting.encode("utf-8")
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self.update_server_events()
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def remove_client(self):
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libvirt.virEventRemoveHandle(self.clientwatch)
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self.clientsock.close()
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self.clientsock = None
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self.clientwatch = 0
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self.update_server_events()
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self.api2sock = bytes([])
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self.api2sockfds = []
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self.sock2api = bytes([])
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self.sock2apifds = []
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def update_client_events(self):
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# For simplicity of tracking distinct QMP cmds and their passed FDs
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# we don't try to support "pipelining", only a single cmd may be
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# inflight
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if len(self.api2sock) > 0:
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events = libvirt.VIR_EVENT_HANDLE_WRITABLE
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else:
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events = libvirt.VIR_EVENT_HANDLE_READABLE
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libvirt.virEventUpdateHandle(self.clientwatch, events)
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def update_server_events(self):
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if self.clientsock is not None:
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libvirt.virEventUpdateHandle(self.serverwatch, 0)
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else:
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libvirt.virEventUpdateHandle(self.serverwatch,
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libvirt.VIR_EVENT_HANDLE_READABLE)
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def try_command(self):
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try:
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cmdstr = self.sock2api.decode("utf-8")
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cmd = json.loads(cmdstr)
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if self.verbose:
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cmdstr = cmdstr.strip()
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print(cmdstr)
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except Exception as ex:
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if debug:
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print("Incomplete %s: %s" % (self.sock2api, ex))
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return
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id = None
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if "id" in cmd:
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id = cmd["id"]
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del cmd["id"]
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if cmd.get("execute", "") == "qmp_capabilities":
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resobj = {
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"return": {},
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}
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resfds = []
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else:
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if hasattr(libvirt_qemu, "qemuMonitorCommandWithFiles"):
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res, resfds = libvirt_qemu.qemuMonitorCommandWithFiles(
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self.dom, json.dumps(cmd), [f.fileno() for f in self.sock2apifds])
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resobj = json.loads(res)
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else:
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if len(self.sock2apifds) > 0:
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raise Exception("FD passing not supported")
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res = libvirt_qemu.qemuMonitorCommand(
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self.dom, json.dumps(cmd))
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resfds = []
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resobj = json.loads(res)
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if "id" in resobj:
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del resobj["id"]
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if id is not None:
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resobj["id"] = id
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res = json.dumps(resobj)
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if self.verbose:
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print(res)
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res += "\r\n"
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self.sock2api = bytes([])
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self.sock2apifds = []
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self.api2sock += res.encode("utf-8")
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self.api2sockfds = resfds
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@staticmethod
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def handle_client_io(watch, fd, events, self):
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error = False
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try:
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if events & libvirt.VIR_EVENT_HANDLE_WRITABLE:
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done = self.send_with_fds(self.api2sock, self.api2sockfds)
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if done > 0:
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self.api2sock = self.api2sock[done:]
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self.api2sockfds = []
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elif events & libvirt.VIR_EVENT_HANDLE_READABLE:
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data, fds = self.recv_with_fds()
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if len(data) == 0:
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error = True
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else:
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self.sock2api += data
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if len(fds):
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self.sock2apifds += fds
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self.try_command()
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else:
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error = True
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except Exception as e:
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global debug
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if debug:
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print("%s: %s" % (sys.argv[0], str(e)))
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print(traceback.format_exc())
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error = True
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if error:
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self.remove_client()
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else:
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self.update_client_events()
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@staticmethod
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def handle_server_io(watch, fd, events, self):
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if self.clientsock is None:
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sock, addr = self.serversock.accept()
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self.add_client(sock)
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else:
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self.update_server_events()
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def parse_commandline():
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parser = argparse.ArgumentParser(description="Libvirt QMP proxy")
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parser.add_argument("--connect", "-c",
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help="Libvirt QEMU driver connection URI")
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parser.add_argument("--debug", "-d", action='store_true',
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help="Display debugging information")
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parser.add_argument("--verbose", "-v", action='store_true',
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help="Display QMP traffic")
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parser.add_argument("domain", metavar="DOMAIN",
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help="Libvirt guest domain ID/UUID/Name")
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parser.add_argument("sockpath", metavar="QMP-SOCK-PATH",
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help="UNIX socket path for QMP server")
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return parser.parse_args()
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def main():
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args = parse_commandline()
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global debug
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debug = args.debug
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if not debug:
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libvirt.registerErrorHandler(lambda opaque, error: None, None)
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libvirt.virEventRegisterDefaultImpl()
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conn, dom = get_domain(args.connect, args.domain)
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if conn.getType() != "QEMU":
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raise Exception("QMP proxy requires a QEMU driver connection not %s" %
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conn.getType())
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sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
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if os.path.exists(args.sockpath):
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os.unlink(args.sockpath)
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sock.bind(args.sockpath)
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sock.listen(1)
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_ = QMPProxy(conn, dom, sock, args.verbose)
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while True:
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libvirt.virEventRunDefaultImpl()
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try:
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main()
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sys.exit(0)
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except Exception as e:
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print("%s: %s" % (sys.argv[0], str(e)))
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if debug:
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print(traceback.format_exc())
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sys.exit(1)
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