Add register-driver option to UpdateDeployment D-Bus API

Record the agent id and agent systemd unit and serialize it into a
JSON file at `/run/rpmostree/update-driver.json`.

Also add the companion `--register-driver` option to the `deploy`
CLI argument.

Closes coreos#1747.

src/app/rpmostree-builtin-deploy.cxx

@@ -35,6 +35,7 @@ static gboolean opt_download_only;
 static gboolean opt_lock_finalization;
 static gboolean opt_disallow_downgrade;
 static gboolean opt_unchanged_exit_77;
+static gboolean opt_register_driver;
 
 static GOptionEntry option_entries[] = {
   { "os", 0, 0, G_OPTION_ARG_STRING, &opt_osname, "Operate on provided OSNAME", "OSNAME" },
@@ -49,6 +50,7 @@ static GOptionEntry option_entries[] = {
   { "lock-finalization", 0, G_OPTION_FLAG_HIDDEN, G_OPTION_ARG_NONE, &opt_lock_finalization, "Prevent automatic deployment finalization on shutdown", NULL },
   { "disallow-downgrade", 0, 0, G_OPTION_ARG_NONE, &opt_disallow_downgrade, "Forbid deployment of chronologically older trees", NULL },
   { "unchanged-exit-77", 0, 0, G_OPTION_ARG_NONE, &opt_unchanged_exit_77, "If no new deployment made, exit 77", NULL },
+  { "register-driver", 0, G_OPTION_FLAG_HIDDEN, G_OPTION_ARG_NONE, &opt_register_driver, "Register the calling agent as the driver for updates", NULL },
   { NULL }
 };
 
@@ -125,6 +127,7 @@ rpmostree_builtin_deploy (int            argc,
       g_variant_dict_insert (&dict, "download-only", "b", opt_download_only);
       g_variant_dict_insert (&dict, "lock-finalization", "b", opt_lock_finalization);
       g_variant_dict_insert (&dict, "initiating-command-line", "s", invocation->command_line);
+      g_variant_dict_insert (&dict, "register-driver", "b", opt_register_driver);
       g_autoptr(GVariant) options = g_variant_ref_sink (g_variant_dict_end (&dict));
 
       /* Use newer D-Bus API only if we have to so we maintain coverage. */

src/daemon/org.projectatomic.rpmostree1.xml

@@ -321,6 +321,8 @@
             Stop short of deploying the new tree. If layering packages,
             the pkg diff is printed but packages are not downloaded or
             imported.
+         "register-driver" (type 'b')
+            Register the caller as the update driver.
          "no-layering" (type 'b')
             Remove all package requests. Requests in "install-packages"
             are still subsequently processed if specified.

src/daemon/rpmostreed-daemon.h

@@ -30,6 +30,12 @@ G_BEGIN_DECLS
 #define DBUS_NAME "org.projectatomic.rpmostree1"
 #define BASE_DBUS_PATH "/org/projectatomic/rpmostree1"
 
+/* Update driver info */
+#define RPMOSTREE_RUN_DIR "/run/rpm-ostree/"
+#define RPMOSTREE_DRIVER_STATE RPMOSTREE_RUN_DIR "update-driver.gv"
+#define RPMOSTREE_DRIVER_AGENT_SD_UNIT "agent-sd-unit"
+#define RPMOSTREE_DRIVER_AGENT_ID "agent-id"
+
 GType              rpmostreed_daemon_get_type       (void) G_GNUC_CONST;
 RpmostreedDaemon * rpmostreed_daemon_get            (void);
 gboolean           rpmostreed_get_client_uid        (RpmostreedDaemon *self,

src/daemon/rpmostreed-transaction-types.cxx

@@ -19,13 +19,16 @@
 #include "config.h"
 #include "ostree.h"
 
+#include <json-glib/json-glib.h>
+#include <gio/gunixoutputstream.h>
 #include <libglnx.h>
 #include <systemd/sd-journal.h>
 
 #include "rpmostreed-transaction-types.h"
 #include "rpmostreed-transaction.h"
 #include "rpmostreed-deployment-utils.h"
 #include "rpmostreed-sysroot.h"
+#include "rpmostreed-daemon.h"
 #include "rpmostree-sysroot-upgrader.h"
 #include "rpmostree-sysroot-core.h"
 #include "rpmostree-rpm-util.h"
@@ -787,6 +790,74 @@ deploy_has_bool_option (DeployTransaction *self,
   return vardict_lookup_bool (self->options, option, FALSE);
 }
 
+/* Write a state file which records information about the agent that is "driving" updates */
+static gboolean
+record_driver_info (const char   *id,
+                    const char   *sd_unit,
+                    GCancellable *cancellable,
+                    GError      **error)
+{
+  g_auto(GVariantBuilder) caller_info_builder;
+  g_variant_builder_init (&caller_info_builder, G_VARIANT_TYPE ("a{sv}"));
+
+  if (id)
+    g_variant_builder_add (&caller_info_builder, "{sv}", RPMOSTREE_DRIVER_AGENT_ID,
+                            g_variant_new_string (id));
+  if (sd_unit)
+    g_variant_builder_add (&caller_info_builder, "{sv}", RPMOSTREE_DRIVER_AGENT_SD_UNIT,
+                           g_variant_new_string (sd_unit));
+
+  g_autoptr(GVariant) driver_info =
+    g_variant_ref_sink (g_variant_builder_end (&caller_info_builder));
+
+  if (!glnx_shutil_mkdir_p_at (AT_FDCWD, RPMOSTREE_RUN_DIR, 0755, cancellable, error))
+    return FALSE;
+  if (!glnx_file_replace_contents_at (AT_FDCWD, RPMOSTREE_DRIVER_STATE,
+                                      static_cast<const guint8*>(g_variant_get_data (driver_info)),
+                                      g_variant_get_size (driver_info),
+                                      static_cast<GLnxFileReplaceFlags>(0), cancellable, error))
+    return FALSE;
+
+  return TRUE;
+}
+
+/* Read from state file that records information about the agent that is "driving" updates */
+gboolean
+get_driver_info (char   **id,
+                 char   **sd_unit,
+                 GError **error)
+{
+  glnx_autofd int fd = -1;
+  g_autoptr(GError) local_error = NULL;
+  if (!glnx_openat_rdonly (AT_FDCWD, RPMOSTREE_DRIVER_STATE, TRUE, &fd,
+                           &local_error))
+    {
+      if (!g_error_matches (local_error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND))
+        return g_propagate_error (error, util::move_nullify (local_error)), FALSE;
+      return TRUE;
+    }
+
+  g_autoptr(GBytes) data = glnx_fd_readall_bytes (fd, NULL, error);
+  if (!data)
+    return FALSE;
+
+  g_autoptr(GVariant) driver_info =
+    g_variant_ref_sink (g_variant_new_from_bytes (G_VARIANT_TYPE_VARDICT, data, FALSE));
+
+  g_auto(GVariantDict) driver_info_dict;
+  g_variant_dict_init (&driver_info_dict, driver_info);
+  auto v = static_cast<char*>(vardict_lookup_ptr (&driver_info_dict,
+                                                  RPMOSTREE_DRIVER_AGENT_ID, "s"));
+  if (v)
+    *id = v;
+  v = static_cast<char*>(vardict_lookup_ptr (&driver_info_dict,
+                                             RPMOSTREE_DRIVER_AGENT_SD_UNIT, "s"));
+  if (v)
+    *sd_unit = v;
+
+  return TRUE;
+}
+
 static gboolean
 deploy_transaction_execute (RpmostreedTransaction *transaction,
                             GCancellable *cancellable,
@@ -797,6 +868,7 @@ deploy_transaction_execute (RpmostreedTransaction *transaction,
 
   const gboolean dry_run =
     ((self->flags & RPMOSTREE_TRANSACTION_DEPLOY_FLAG_DRY_RUN) > 0);
+  const gboolean register_driver = deploy_has_bool_option (self, "register-driver");
   const gboolean no_overrides = deploy_has_bool_option (self, "no-overrides");
   const gboolean no_layering = deploy_has_bool_option (self, "no-layering");
   const gboolean no_initramfs = deploy_has_bool_option (self, "no-initramfs");
@@ -1332,6 +1404,14 @@ deploy_transaction_execute (RpmostreedTransaction *transaction,
     return FALSE;
   changed = changed || layering_changed;
 
+  if (register_driver)
+    {
+      if (!record_driver_info (rpmostreed_transaction_get_agent_id (transaction),
+                               rpmostreed_transaction_get_sd_unit (transaction),
+                               cancellable, error))
+        return FALSE;
+    }
+
   if (dry_run)
     /* Note early return here; we printed the transaction already */
     return TRUE;

src/daemon/rpmostreed-transaction-types.h

@@ -157,3 +157,8 @@ rpmostreed_transaction_new_kernel_arg (GDBusMethodInvocation *invocation,
                                        GError               **error);
 
 G_END_DECLS
+
+gboolean
+get_driver_info (char   **id,
+                 char   **sd_unit,
+                 GError **error);