[PATCH v4 22/32] libxl_qmp: Handle messages from QEMU

[Anthony PERARD <anthony.perard@citrix.com>]

This will handles messages received, and calls callbacks associated with
the libxl__ev_qmp when the expected response is received.

This also print error messages from QMP on behalf of the callback.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
---

Notes:
    v4:
        Provide an libxl error code to callbacks on error instead of a
        qmp_error_class

 tools/libxl/libxl_qmp.c              | 116 +++++++++++++++++++++++++++
 tools/libxl/libxl_types.idl          |   4 +
 tools/libxl/libxl_types_internal.idl |   8 ++
 3 files changed, 128 insertions(+)

diff --git a/tools/libxl/libxl_qmp.c b/tools/libxl/libxl_qmp.c
index aabf9ad5e7..e649b8054d 100644
--- a/tools/libxl/libxl_qmp.c
+++ b/tools/libxl/libxl_qmp.c
@@ -1330,6 +1330,118 @@ static int qmp_ev_prepare_cmd(libxl__gc *gc,
     return 0;
 }
 
+/*
+ * Handle messages received from QMP server
+ */
+
+static int qmp_error_class_to_libxl_error_code(const libxl__qmp_error_class c)
+{
+    switch (c) {
+    case LIBXL__QMP_ERROR_CLASS_GENERICERROR:
+        return ERROR_QMP_GENERIC_ERROR;
+    case LIBXL__QMP_ERROR_CLASS_COMMANDNOTFOUND:
+        return ERROR_QMP_COMMAND_NOT_FOUND;
+    case LIBXL__QMP_ERROR_CLASS_DEVICENOTACTIVE:
+        return ERROR_QMP_DEVICE_NOT_ACTIVE;
+    case LIBXL__QMP_ERROR_CLASS_DEVICENOTFOUND:
+        return ERROR_QMP_DEVICE_NOT_FOUND;
+    default:
+        abort();
+    }
+}
+
+/* return 1 when a user callback as been called */
+static int qmp_ev_handle_response(libxl__egc *egc,
+                                  libxl__ev_qmp *ev,
+                                  const libxl__json_object *resp,
+                                  libxl__qmp_message_type type)
+{
+    EGC_GC;
+    const libxl__json_object *response;
+    const libxl__json_object *o;
+    int rc;
+    int id;
+
+    o = libxl__json_map_get("id", resp, JSON_INTEGER);
+    if (!o) {
+        const char *error_desc;
+
+        /* unexpected message, attempt to find an error description */
+        o = libxl__json_map_get("error", resp, JSON_MAP);
+        o = libxl__json_map_get("desc", o, JSON_STRING);
+        error_desc = libxl__json_object_get_string(o);
+        if (error_desc)
+            LOGD(ERROR, ev->domid, "%s", error_desc);
+        else
+            LOGD(ERROR, ev->domid, "Received unexpected message: %s",
+                 libxl__json_object_to_json(gc, resp));
+        return 0;
+    }
+
+    id = libxl__json_object_get_integer(o);
+    if (id != ev->id)
+        return 0;
+
+    switch (type) {
+    case LIBXL__QMP_MESSAGE_TYPE_RETURN: {
+        response = libxl__json_map_get("return", resp, JSON_ANY);
+        rc = 0;
+        break;
+    }
+    case LIBXL__QMP_MESSAGE_TYPE_ERROR: {
+        const char *s;
+        const libxl__json_object *err;
+        libxl__qmp_error_class error_class;
+
+        rc = ERROR_FAIL;
+        response = NULL;
+
+        err = libxl__json_map_get("error", resp, JSON_MAP);
+        o = libxl__json_map_get("class", err, JSON_STRING);
+        s = libxl__json_object_get_string(o);
+        if (s && !libxl__qmp_error_class_from_string(s, &error_class))
+            rc = qmp_error_class_to_libxl_error_code(error_class);
+
+        o = libxl__json_map_get("desc", err, JSON_STRING);
+        s = libxl__json_object_get_string(o);
+        if (s)
+            LOGD(ERROR, ev->domid, "%s", s);
+
+        break;
+    }
+    default:
+        abort();
+    }
+
+    ev->id = -1;
+    ev->callback(egc, ev, response, rc); /* must be last */
+    return 1;
+}
+
+/* return 1 when a user callback as been called */
+static int qmp_ev_handle_message(libxl__egc *egc,
+                                 libxl__ev_qmp *ev,
+                                 const libxl__json_object *resp)
+{
+    EGC_GC;
+    libxl__qmp_message_type type = qmp_response_type(resp);
+
+    switch (type) {
+    case LIBXL__QMP_MESSAGE_TYPE_QMP:
+        /* greeting message */
+        return 0;
+    case LIBXL__QMP_MESSAGE_TYPE_RETURN:
+    case LIBXL__QMP_MESSAGE_TYPE_ERROR:
+        return qmp_ev_handle_response(egc, ev, resp, type);
+    case LIBXL__QMP_MESSAGE_TYPE_EVENT:
+        /* Event are ignored */
+        return 0;
+    case LIBXL__QMP_MESSAGE_TYPE_INVALID:
+        return 0;
+    }
+    return 0;
+}
+
 /*
  * QMP FD callbacks
  */
@@ -1432,6 +1544,10 @@ static int qmp_ev_callback_readable(libxl__egc *egc, libxl__ev_qmp *ev, int fd)
             end = NULL;
 
         LOG_QMP("JSON object received: %s", libxl__json_object_to_json(gc, o));
+
+        /* Must be last and return when the user callback is called */
+        if (qmp_ev_handle_message(egc, ev, o) == 1)
+            return 0;
     }
     return 0;
 }
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index 4a385801ba..e104fea941 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -69,6 +69,10 @@ libxl_error = Enumeration("error", [
     (-23, "NOTFOUND"),
     (-24, "DOMAIN_DESTROYED"), # Target domain ceased to exist during op
     (-25, "FEATURE_REMOVED"), # For functionality that has been removed
+    (-26, "QMP_GENERIC_ERROR"), # unspecified qmp error
+    (-27, "QMP_COMMAND_NOT_FOUND"), # the requested command has not been found
+    (-28, "QMP_DEVICE_NOT_ACTIVE"), # a device has failed to be become active
+    (-29, "QMP_DEVICE_NOT_FOUND"), # the requested device has not been found
     ], value_namespace = "")
 
 libxl_domain_type = Enumeration("domain_type", [
diff --git a/tools/libxl/libxl_types_internal.idl b/tools/libxl/libxl_types_internal.idl
index 37402e49cb..1536d02215 100644
--- a/tools/libxl/libxl_types_internal.idl
+++ b/tools/libxl/libxl_types_internal.idl
@@ -13,6 +13,14 @@ libxl__qmp_message_type = Enumeration("qmp_message_type", [
     (5, "invalid"),
     ])
 
+libxl__qmp_error_class = Enumeration("qmp_error_class", [
+    # QMP error classes described in QEMU sources code (QapiErrorClass)
+    (1, "GenericError"),
+    (2, "CommandNotFound"),
+    (3, "DeviceNotActive"),
+    (4, "DeviceNotFound"),
+    ])
+
 libxl__device_kind = Enumeration("device_kind", [
     (0, "NONE"),
     (1, "VIF"),
-- 
Anthony PERARD


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