various: treat BUS_ERROR_NO_SUCH_UNIT the same as SD_BUS_ERROR_SERVICE_UNKNOWN

We return BUS_ERROR_NO_SUCH_UNIT a.k.a. org.freedesktop.systemd1.NoSuchUnit
in various places. In #16813:
Aug 22 06:14:48 core sudo[2769199]: pam_systemd_home(sudo:account): Failed to query user record: Unit dbus-org.freedesktop.home1.service not found.
Aug 22 06:14:48 core dbus-daemon[5311]: [system] Activation via systemd failed for unit 'dbus-org.freedesktop.home1.service': Unit dbus-org.freedesktop.home1.service not found.
Aug 22 06:14:48 core dbus-daemon[5311]: [system] Activating via systemd: service name='org.freedesktop.home1' unit='dbus-org.freedesktop.home1.service' requested by ':1.6564' (uid=0 pid=2769199 comm="sudo su ")

This particular error comes from bus_unit_validate_load_state() in pid1:
  case UNIT_NOT_FOUND:
       return sd_bus_error_setf(error, BUS_ERROR_NO_SUCH_UNIT, "Unit %s not found.", u->id);

It seems possible that we should return a different error, but it doesn't really
matter: if we change pid1 to return a different error, we still need to handle
BUS_ERROR_NO_SUCH_UNIT as in this patch to handle pid1 with current code.

1 files changed, 8 insertions, 2 deletions

diff --git a/src/shared/bus-util.c b/src/shared/bus-util.c
index 77c1c62182..9a306daa03 100644
--- a/src/shared/bus-util.c
+++ b/src/shared/bus-util.c
@@ -14,14 +14,13 @@
 #include "sd-event.h"
 #include "sd-id128.h"
 
-/* #include "alloc-util.h" */
+#include "bus-common-errors.h"
 #include "bus-internal.h"
 #include "bus-label.h"
 #include "bus-util.h"
 #include "path-util.h"
 #include "socket-util.h"
 #include "stdio-util.h"
-/* #include "string-util.h" */
 
 static int name_owner_change_callback(sd_bus_message *m, void *userdata, sd_bus_error *ret_error) {
         sd_event *e = userdata;
@@ -153,6 +152,13 @@ int bus_name_has_owner(sd_bus *c, const char *name, sd_bus_error *error) {
         return has_owner;
 }
 
+bool bus_error_is_unknown_service(const sd_bus_error *error) {
+        return sd_bus_error_has_names(error,
+                                      SD_BUS_ERROR_SERVICE_UNKNOWN,
+                                      SD_BUS_ERROR_NAME_HAS_NO_OWNER,
+                                      BUS_ERROR_NO_SUCH_UNIT);
+}
+
 int bus_check_peercred(sd_bus *c) {
         struct ucred ucred;
         int fd, r;