systemctl: add new option to mount image inside a running service namespace

Use the new DBUS method and follow the same pattern as the
systemctl bind command.

src/systemctl/systemctl-mount.c

@@ -2,6 +2,7 @@
 
 #include "bus-error.h"
 #include "bus-locator.h"
+#include "dissect-image.h"
 #include "systemctl-mount.h"
 #include "systemctl-util.h"
 #include "systemctl.h"
@@ -39,3 +40,77 @@ int mount_bind(int argc, char *argv[], void *userdata) {
 
         return 0;
 }
+
+int mount_image(int argc, char *argv[], void *userdata) {
+        _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+        const char *unit = argv[1], *src = argv[2], *dest = argv[3];
+        _cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL;
+        _cleanup_free_ char *n = NULL;
+        sd_bus *bus;
+        int r;
+
+        r = acquire_bus(BUS_MANAGER, &bus);
+        if (r < 0)
+                return r;
+
+        polkit_agent_open_maybe();
+
+        r = unit_name_mangle(unit, arg_quiet ? 0 : UNIT_NAME_MANGLE_WARN, &n);
+        if (r < 0)
+                return log_error_errno(r, "Failed to mangle unit name: %m");
+
+        r = bus_message_new_method_call(
+                        bus,
+                        &m,
+                        bus_systemd_mgr,
+                        "MountImageUnit");
+        if (r < 0)
+                return bus_log_create_error(r);
+
+        r = sd_bus_message_append(
+                        m,
+                        "sssbb",
+                        n,
+                        src,
+                        dest,
+                        arg_read_only,
+                        arg_mkdir);
+        if (r < 0)
+                return bus_log_create_error(r);
+
+        r = sd_bus_message_open_container(m, 'a', "(ss)");
+        if (r < 0)
+                return bus_log_create_error(r);
+
+        if (argc > 4) {
+                _cleanup_free_ char *partition = NULL, *mount_options = NULL;
+                const char *options = argv[4];
+
+                r = extract_many_words(&options, ":", EXTRACT_CUNESCAPE|EXTRACT_UNESCAPE_SEPARATORS, &partition, &mount_options, NULL);
+                if (r < 0)
+                        return r;
+                /* Single set of options, applying to the root partition/single filesystem */
+                if (r == 1) {
+                        r = sd_bus_message_append(m, "(ss)", "root", partition);
+                        if (r < 0)
+                                return bus_log_create_error(r);
+                } else if (r > 1) {
+                        if (partition_designator_from_string(partition) < 0)
+                                return bus_log_create_error(-EINVAL);
+
+                        r = sd_bus_message_append(m, "(ss)", partition, mount_options);
+                        if (r < 0)
+                                return bus_log_create_error(r);
+                }
+        }
+
+        r = sd_bus_message_close_container(m);
+        if (r < 0)
+                return bus_log_create_error(r);
+
+        r = sd_bus_call(bus, m, -1, &error, NULL);
+        if (r < 0)
+                return log_error_errno(r, "Failed to mount image: %s", bus_error_message(&error, r));
+
+        return 0;
+}