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/rpmostree-sysroot-core.h

@@ -37,6 +37,9 @@ G_BEGIN_DECLS
  * /run/ostree/staged-deployment path and company. */
 #define _OSTREE_SYSROOT_RUNSTATE_STAGED_LOCKED "/run/ostree/staged-deployment-locked"
 
+/* File to store update driver info */
+#define RPMOSTREE_DRIVER_STATE "/run/rpmostree/update-driver.json"
+
 gboolean
 rpmostree_syscore_cleanup (OstreeSysroot            *sysroot,
                            OstreeRepo               *repo,

src/daemon/rpmostreed-transaction-types.cxx

@@ -19,6 +19,8 @@
 #include "config.h"
 #include "ostree.h"
 
+#include <json-glib/json-glib.h>
+#include <gio/gunixoutputstream.h>
 #include <libglnx.h>
 #include <systemd/sd-journal.h>
 
@@ -787,6 +789,48 @@ deploy_has_bool_option (DeployTransaction *self,
   return vardict_lookup_bool (self->options, option, FALSE);
 }
 
+static gboolean
+record_driver_info (const char   *agent,
+                    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 (agent_id)
+    g_variant_builder_add (&caller_info_builder, "{sv}", "agent-id",
+                            g_variant_new_string (agent));
+  if (sd_unit)
+    g_variant_builder_add (&caller_info_builder, "{sv}", "agent-sd-unit",
+                           g_variant_new_string (sd_unit));
+
+  g_autoptr(GVariant) composemeta_v = g_variant_builder_end (&caller_info_builder);
+  JsonNode *composemeta_node = json_gvariant_serialize (composemeta_v);
+  glnx_unref_object JsonGenerator *generator = json_generator_new ();
+  json_generator_set_root (generator, composemeta_node);
+
+  char *dnbuf = strdupa (RPMOSTREE_DRIVER_STATE);
+  const char *dn = dirname (dnbuf);
+  if (!glnx_shutil_mkdir_p_at (AT_FDCWD, dn,
+                               0755, cancellable, error))
+    return FALSE;
+  g_auto(GLnxTmpfile) tmpf = { 0, };
+  if (!glnx_open_tmpfile_linkable_at (AT_FDCWD, dn, O_WRONLY | O_CLOEXEC,
+                                      &tmpf, error))
+    return FALSE;
+  g_autoptr(GOutputStream) out = g_unix_output_stream_new (tmpf.fd, FALSE);
+  if (json_generator_to_stream (generator, out, cancellable, error) <= 0
+      || (error != NULL && *error != NULL))
+    return FALSE;
+
+  if (!glnx_link_tmpfile_at (&tmpf, GLNX_LINK_TMPFILE_REPLACE,
+                             AT_FDCWD, RPMOSTREE_DRIVER_STATE, error))
+        return FALSE;
+
+  return TRUE;
+}
+
 static gboolean
 deploy_transaction_execute (RpmostreedTransaction *transaction,
                             GCancellable *cancellable,
@@ -797,6 +841,7 @@ 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 +1377,14 @@ 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;