Re: [libvirt PATCH v3] tools: add virt-qemu-qmp-proxy for proxying QMP via libvirt QEMU guests

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(a)redhat.com&gt; --- In v3: - Added to libvirt-clients-qemu RPM - Renamed to virt-qemu-qmp-proxy docs/manpages/meson.build | 1 + docs/manpages/virt-qemu-qmp-proxy.rst | 120 +++++++++ libvirt.spec.in | 15 ++ tools/meson.build | 5 + tools/virt-qemu-qmp-proxy | 360 ++++++++++++++++++++++++++ 5 files changed, 501 insertions(+) create mode 100644 docs/manpages/virt-qemu-qmp-proxy.rst create mode 100755 tools/virt-qemu-qmp-proxy

diff --git a/tools/virt-qemu-qmp-proxy b/tools/virt-qemu-qmp-proxy new file mode 100755 index 0000000000..d85342bd2b --- /dev/null +++ b/tools/virt-qemu-qmp-proxy

+ @staticmethod + def make_file(fd): + flags = fcntl.fcntl(fd, fcntl.F_GETFL) + + mask = os.O_RDONLY | os.O_WRONLY | os.O_RDWR | os.O_APPEND + flags = flags & mask + mode = "" + if flags == os.O_RDONLY: + mode = "rb" + elif flags == os.O_WRONLY: + mode = "wb" + elif flags == os.O_RDWR: + mode = "r+b" + elif flags == (os.O_WRONLY | os.O_APPEND): + mode = "ab" + elif flags == (os.O_RDWR | os.O_APPEND): + mode = "a+b" + + return os.fdopen(fd, mode)