bus: when we cannot bus activate a service because we go down, drop one

message from the queue

TODO

@@ -166,7 +166,6 @@ Features:
   - bus proxy should fake seclabel when connecting to kdbus
   - allow updating attach flags during runtime
   - pid1: peek into activating message when activating a service
-  - when service activation failed, drop one message from the activator queue
 
 * sd-event
   - allow multiple signal handlers per signal?

src/core/busname.c

@@ -337,8 +337,8 @@ static void busname_enter_running(BusName *n) {
                 log_debug_unit(UNIT(n)->id, "Suppressing activation request on %s since unit stop is scheduled.", UNIT(n)->id);
 
                 /* Flush all queued activation reqeuest by closing and reopening the connection */
+                bus_kernel_drop_one(n->starter_fd);
 
-                busname_close_fd(n);
                 busname_enter_listening(n);
                 return;
         }

src/libsystemd/sd-bus/bus-kernel.c

@@ -1476,3 +1476,16 @@ int bus_kernel_try_close(sd_bus *bus) {
 
         return 0;
 }
+
+int bus_kernel_drop_one(int fd) {
+        struct kdbus_cmd_recv recv = {
+                .flags = KDBUS_RECV_DROP
+        };
+
+        assert(fd >= 0);
+
+        if (ioctl(fd, KDBUS_CMD_MSG_RECV, &recv) < 0)
+                return -errno;
+
+        return 0;
+}

src/libsystemd/sd-bus/bus-kernel.h

@@ -79,3 +79,5 @@ int kdbus_translate_request_name_flags(uint64_t sd_bus_flags, uint64_t *kdbus_fl
 int kdbus_translate_attach_flags(uint64_t sd_bus_flags, uint64_t *kdbus_flags);
 
 int bus_kernel_try_close(sd_bus *bus);
+
+int bus_kernel_drop_one(int fd);