libxl: libxl__qmp_migrate

This command works in two steps. First, a fd is sent to QEMU through the QMP
socket. And then, the second command "migrate" use the fd previously sent to
ask QEMU to save its states.

This comes with an alternative qmp_send function that can send a fd.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Ian Jackson <ian.jackson.citrix.com>
Committed-by: Ian Jackson <ian.jackson.citrix.com>

diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 6ce34fd67aef4db3322f0ccac36a2a7421959239..d8ce656f9dcfd909b16378d73f669c467a5accfb 100644 (file)
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -527,6 +527,8 @@ _hidden int libxl__qmp_query_serial(libxl__qmp_handler *qmp);
 _hidden int libxl__qmp_pci_add(libxl__gc *gc, int d, libxl_device_pci *pcidev);
 _hidden int libxl__qmp_pci_del(libxl__gc *gc, int domid,
                                libxl_device_pci *pcidev);
+/* Save current QEMU state into fd. */
+_hidden int libxl__qmp_migrate(libxl__gc *gc, int domid, int fd);
 /* close and free the QMP handler */
 _hidden void libxl__qmp_close(libxl__qmp_handler *qmp);
 /* remove the socket file, if the file has already been removed,

diff --git a/tools/libxl/libxl_qmp.c b/tools/libxl/libxl_qmp.c
index 4c261369d52fcb36c6a352db9a4a5239e5139cef..4bc0dc87ae15d98e65eb3fe67f367d2a59521df9 100644 (file)
--- a/tools/libxl/libxl_qmp.c
+++ b/tools/libxl/libxl_qmp.c
@@ -532,6 +532,52 @@ out:
     return rc;
 }
 
+static int qmp_send_fd(libxl__gc *gc, libxl__qmp_handler *qmp,
+                       libxl_key_value_list *args,
+                       qmp_callback_t callback, void *opaque,
+                       qmp_request_context *context,
+                       int fd)
+{
+    struct msghdr msg = { 0 };
+    struct cmsghdr *cmsg;
+    char control[CMSG_SPACE(sizeof (fd))];
+    struct iovec iov;
+    char *buf = NULL;
+
+    buf = qmp_send_prepare(gc, qmp, "getfd", args, callback, opaque, context);
+
+    /* Response data */
+    iov.iov_base = buf;
+    iov.iov_len  = strlen(buf);
+
+    /* compose the message */
+    msg.msg_iov = &iov;
+    msg.msg_iovlen = 1;
+    msg.msg_control = control;
+    msg.msg_controllen = sizeof (control);
+
+    /* attach open fd */
+    cmsg = CMSG_FIRSTHDR(&msg);
+    cmsg->cmsg_level = SOL_SOCKET;
+    cmsg->cmsg_type = SCM_RIGHTS;
+    cmsg->cmsg_len = CMSG_LEN(sizeof (fd));
+    *(int *)CMSG_DATA(cmsg) = fd;
+
+    msg.msg_controllen = cmsg->cmsg_len;
+
+    if (sendmsg(qmp->qmp_fd, &msg, 0) < 0) {
+        LIBXL__LOG_ERRNO(qmp->ctx, LIBXL__LOG_ERROR,
+                         "Failed to send a QMP message to QEMU.");
+        return ERROR_FAIL;
+    }
+    if (libxl_write_exactly(qmp->ctx, qmp->qmp_fd, "\r\n", 2,
+                            "CRLF", "QMP socket")) {
+        return ERROR_FAIL;
+    }
+
+    return qmp->last_id_used;
+}
+
 static int qmp_synchronous_send(libxl__qmp_handler *qmp, const char *cmd,
                                 libxl_key_value_list *args,
                                 qmp_callback_t callback, void *opaque,
@@ -768,6 +814,69 @@ int libxl__qmp_pci_del(libxl__gc *gc, int domid, libxl_device_pci *pcidev)
     return qmp_device_del(gc, domid, id);
 }
 
+static int qmp_getfd(libxl__gc *gc, libxl__qmp_handler *qmp,
+                     int fd, const char *name)
+{
+    flexarray_t *parameters = NULL;
+    libxl_key_value_list args = NULL;
+    int rc = 0;
+
+    parameters = flexarray_make(2, 1);
+    if (!parameters)
+        return ERROR_NOMEM;
+    flexarray_append_pair(parameters, "fdname", (char*)name);
+    args = libxl__xs_kvs_of_flexarray(gc, parameters, parameters->count);
+    if (!args) {
+        rc = ERROR_NOMEM;
+        goto out;
+    }
+
+    if (qmp_send_fd(gc, qmp, &args, NULL, NULL, NULL, fd) < 0) {
+        rc = ERROR_FAIL;
+    }
+out:
+    flexarray_free(parameters);
+    return rc;
+}
+
+int libxl__qmp_migrate(libxl__gc *gc, int domid, int fd)
+{
+#define MIGRATE_FD_NAME "dm-migrate"
+    libxl__qmp_handler *qmp = NULL;
+    flexarray_t *parameters = NULL;
+    libxl_key_value_list args = NULL;
+    int rc = 0;
+
+    qmp = libxl__qmp_initialize(libxl__gc_owner(gc), domid);
+    if (!qmp)
+        return ERROR_FAIL;
+
+    rc = qmp_getfd(gc, qmp, fd, MIGRATE_FD_NAME);
+    if (rc)
+        goto out;
+
+    parameters = flexarray_make(2, 1);
+    if (!parameters) {
+        rc = ERROR_NOMEM;
+        goto out;
+    }
+    flexarray_append_pair(parameters, "uri", "fd:" MIGRATE_FD_NAME);
+    args = libxl__xs_kvs_of_flexarray(gc, parameters, parameters->count);
+    if (!args) {
+        rc = ERROR_NOMEM;
+        goto out2;
+    }
+
+    rc = qmp_synchronous_send(qmp, "migrate", &args,
+                              NULL, NULL, qmp->timeout);
+
+out2:
+    flexarray_free(parameters);
+out:
+    libxl__qmp_close(qmp);
+    return rc;
+}
+
 int libxl__qmp_initializations(libxl_ctx *ctx, uint32_t domid)
 {
     libxl__qmp_handler *qmp = NULL;