Christian Brauner
50dd55bb6e
Async QMP client for talking to QEMU's machine monitor from
libsystemd-shared. The I/O core (buffered read/write, output queue,
event source management) follows sd-varlink's patterns.
State machine:
INITIAL -> GREETING_RECEIVED -> CAPABILITIES_SENT -> RUNNING
|
v
DISCONNECTED
The QMP handshake (greeting + qmp_capabilities) is driven transparently
by qmp_client_invoke() through an internal qmp_client_ensure_running()
helper, matching sd-bus's bus_ensure_running() pattern. Callers never
wait for it explicitly.
qmp_client_invoke() is the only command interface: asynchronous, with
per-command callback. Slots are tracked in a Set keyed by id; replies
are dispatched by id match. SCM_RIGHTS fd passing is bundled through
QmpClientArgs and the QMP_CLIENT_ARGS_FD macro.
qmp_client_process() and qmp_client_wait() are exposed publicly,
mirroring sd_varlink_process() and sd_varlink_wait(). Callers that
need to drive the client synchronously — e.g. feature probing before
entering the sd_event main loop — can loop on them exactly like
varlink_call_internal() does on its varlink equivalents.
Other features:
- Buffered stream reader for QMP's \r\n-delimited JSON, handling
multi-read responses (query-qmp-schema is ~200 KiB).
- Fdset id allocation via qmp_client_next_fdset_id().
- Synthetic SHUTDOWN event on unexpected disconnect.
- Disconnect detection with callback notification and pending-command
cleanup.
- -ENOBUFS from the 16 MiB input-buffer cap is treated as recoverable
(not a transport error).
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
System and Service Manager
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