From: Nathaniel McCallum <npmccallum@redhat.com>
Date: Mon, 22 Jan 2018 21:26:44 +0000 (-0500)
Subject: Add support for SD_BUS_DEFAULT*
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=commitdiff_plain;h=8b42f5e6cdc1c819741ef9492b7cec23971ccc4c;p=elogind.git

Add support for SD_BUS_DEFAULT*

Currently, sd-bus supports the ability to have thread-local default busses.
However, this is less useful than it can be since all functions which
require an sd_bus* as input require the caller to pass it. This patch adds
a new macro which allows the developer to pass a constant SD_BUS_DEFAULT,
SD_BUS_DEFAULT_USER or SD_BUS_DEFAULT_SYSTEM instead. This reduces work for
the caller.

For example:

    r = sd_bus_default(&bus);
    r = sd_bus_call_method(bus, ...);
    sd_bus_unref(bus);

Becomes:

    r = sd_bus_call_method(SD_BUS_DEFAULT, ...);

If the specified thread-local default bus does not exist, the function
calls will return -ENOPKG. No bus will ever be implicitly created.
---

diff --git a/src/libelogind/sd-bus/bus-control.c b/src/libelogind/sd-bus/bus-control.c
index 819128cbd..09b934e7f 100644
--- a/src/libelogind/sd-bus/bus-control.c
+++ b/src/libelogind/sd-bus/bus-control.c
@@ -43,6 +43,7 @@ _public_ int sd_bus_get_unique_name(sd_bus *bus, const char **unique) {
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(unique, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -105,6 +106,7 @@ _public_ int sd_bus_request_name(
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(name, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -208,6 +210,7 @@ _public_ int sd_bus_request_name_async(
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(name, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -261,6 +264,7 @@ _public_ int sd_bus_release_name(
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(name, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -353,6 +357,7 @@ _public_ int sd_bus_release_name_async(
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(name, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -379,6 +384,7 @@ _public_ int sd_bus_list_names(sd_bus *bus, char ***acquired, char ***activatabl
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(acquired || activatable, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -450,6 +456,7 @@ _public_ int sd_bus_get_name_creds(
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(name, -EINVAL);
         assert_return((mask & ~SD_BUS_CREDS_AUGMENT) <= _SD_BUS_CREDS_ALL, -EOPNOTSUPP);
         assert_return(mask == 0 || creds, -EINVAL);
@@ -742,6 +749,7 @@ _public_ int sd_bus_get_owner_creds(sd_bus *bus, uint64_t mask, sd_bus_creds **r
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return((mask & ~SD_BUS_CREDS_AUGMENT) <= _SD_BUS_CREDS_ALL, -EOPNOTSUPP);
         assert_return(ret, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
@@ -900,6 +908,7 @@ _public_ int sd_bus_get_name_machine_id(sd_bus *bus, const char *name, sd_id128_
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(name, -EINVAL);
         assert_return(machine, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
diff --git a/src/libelogind/sd-bus/bus-convenience.c b/src/libelogind/sd-bus/bus-convenience.c
index 7d702e637..8da6640ca 100644
--- a/src/libelogind/sd-bus/bus-convenience.c
+++ b/src/libelogind/sd-bus/bus-convenience.c
@@ -36,6 +36,7 @@ _public_ int sd_bus_emit_signal(
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         if (!BUS_IS_OPEN(bus->state))
@@ -73,6 +74,7 @@ _public_ int sd_bus_call_method_async(
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         if (!BUS_IS_OPEN(bus->state))
@@ -646,6 +648,7 @@ _public_ int sd_bus_match_signal(
         const char *expression;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
         assert_return(!sender || service_name_is_valid(sender), -EINVAL);
         assert_return(!path || object_path_is_valid(path), -EINVAL);
@@ -671,6 +674,7 @@ _public_ int sd_bus_match_signal_async(
         const char *expression;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
         assert_return(!sender || service_name_is_valid(sender), -EINVAL);
         assert_return(!path || object_path_is_valid(path), -EINVAL);
diff --git a/src/libelogind/sd-bus/bus-internal.h b/src/libelogind/sd-bus/bus-internal.h
index d43d3dcac..0aba53634 100644
--- a/src/libelogind/sd-bus/bus-internal.h
+++ b/src/libelogind/sd-bus/bus-internal.h
@@ -370,6 +370,8 @@ const char *bus_message_type_to_string(uint8_t u) _pure_;
 
 #define error_name_is_valid interface_name_is_valid
 
+sd_bus *bus_resolve(sd_bus *bus);
+
 int bus_ensure_running(sd_bus *bus);
 int bus_start_running(sd_bus *bus);
 int bus_next_address(sd_bus *bus);
diff --git a/src/libelogind/sd-bus/bus-objects.c b/src/libelogind/sd-bus/bus-objects.c
index 1237819b4..6e00255b2 100644
--- a/src/libelogind/sd-bus/bus-objects.c
+++ b/src/libelogind/sd-bus/bus-objects.c
@@ -1547,6 +1547,7 @@ static int bus_add_object(
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(object_path_is_valid(path), -EINVAL);
         assert_return(callback, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
@@ -1650,6 +1651,7 @@ static int add_object_vtable_internal(
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(object_path_is_valid(path), -EINVAL);
         assert_return(interface_name_is_valid(interface), -EINVAL);
         assert_return(vtable, -EINVAL);
@@ -1859,6 +1861,7 @@ _public_ int sd_bus_add_node_enumerator(
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(object_path_is_valid(path), -EINVAL);
         assert_return(callback, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
@@ -2110,6 +2113,7 @@ _public_ int sd_bus_emit_properties_changed_strv(
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(object_path_is_valid(path), -EINVAL);
         assert_return(interface_name_is_valid(interface), -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
@@ -2156,6 +2160,7 @@ _public_ int sd_bus_emit_properties_changed(
         char **names;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(object_path_is_valid(path), -EINVAL);
         assert_return(interface_name_is_valid(interface), -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
@@ -2340,6 +2345,7 @@ _public_ int sd_bus_emit_object_added(sd_bus *bus, const char *path) {
          */
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(object_path_is_valid(path), -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -2510,6 +2516,7 @@ _public_ int sd_bus_emit_object_removed(sd_bus *bus, const char *path) {
          */
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(object_path_is_valid(path), -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -2663,6 +2670,7 @@ _public_ int sd_bus_emit_interfaces_added_strv(sd_bus *bus, const char *path, ch
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(object_path_is_valid(path), -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -2729,6 +2737,7 @@ _public_ int sd_bus_emit_interfaces_added(sd_bus *bus, const char *path, const c
         char **interfaces;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(object_path_is_valid(path), -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -2746,6 +2755,7 @@ _public_ int sd_bus_emit_interfaces_removed_strv(sd_bus *bus, const char *path,
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(object_path_is_valid(path), -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -2780,6 +2790,7 @@ _public_ int sd_bus_emit_interfaces_removed(sd_bus *bus, const char *path, const
         char **interfaces;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(object_path_is_valid(path), -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -2797,6 +2808,7 @@ _public_ int sd_bus_add_object_manager(sd_bus *bus, sd_bus_slot **slot, const ch
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(object_path_is_valid(path), -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
diff --git a/src/libelogind/sd-bus/bus-track.c b/src/libelogind/sd-bus/bus-track.c
index 0dd06e9b9..5482d39a0 100644
--- a/src/libelogind/sd-bus/bus-track.c
+++ b/src/libelogind/sd-bus/bus-track.c
@@ -136,6 +136,7 @@ _public_ int sd_bus_track_new(
         sd_bus_track *t;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(track, -EINVAL);
 
         if (!bus->bus_client)
diff --git a/src/libelogind/sd-bus/sd-bus.c b/src/libelogind/sd-bus/sd-bus.c
index 0a43324b9..505ce1337 100644
--- a/src/libelogind/sd-bus/sd-bus.c
+++ b/src/libelogind/sd-bus/sd-bus.c
@@ -85,6 +85,64 @@ static thread_local sd_bus *default_user_bus = NULL;
 #endif // 0
 static thread_local sd_bus *default_starter_bus = NULL;
 
+static sd_bus **bus_choose_default(int (**bus_open)(sd_bus **)) {
+        const char *e;
+
+        /* Let's try our best to reuse another cached connection. If
+         * the starter bus type is set, connect via our normal
+         * connection logic, ignoring $DBUS_STARTER_ADDRESS, so that
+         * we can share the connection with the user/system default
+         * bus. */
+
+        e = secure_getenv("DBUS_STARTER_BUS_TYPE");
+        if (e) {
+                if (streq(e, "system")) {
+                        if (bus_open)
+                                *bus_open = sd_bus_open_system;
+                        return &default_system_bus;
+                } else if (STR_IN_SET(e, "user", "session")) {
+                        if (bus_open)
+                                *bus_open = sd_bus_open_user;
+                        return &default_user_bus;
+                }
+        }
+
+        /* No type is specified, so we have not other option than to
+         * use the starter address if it is set. */
+        e = secure_getenv("DBUS_STARTER_ADDRESS");
+        if (e) {
+                if (bus_open)
+                        *bus_open = sd_bus_open;
+                return &default_starter_bus;
+        }
+
+        /* Finally, if nothing is set use the cached connection for
+         * the right scope */
+
+        if (cg_pid_get_owner_uid(0, NULL) >= 0) {
+                if (bus_open)
+                        *bus_open = sd_bus_open_user;
+                return &default_user_bus;
+        } else {
+                if (bus_open)
+                        *bus_open = sd_bus_open_system;
+                return &default_system_bus;
+        }
+}
+
+sd_bus *bus_resolve(sd_bus *bus) {
+        switch ((uintptr_t) bus) {
+        case (uintptr_t) SD_BUS_DEFAULT:
+                return *(bus_choose_default(NULL));
+        case (uintptr_t) SD_BUS_DEFAULT_USER:
+                return default_user_bus;
+        case (uintptr_t) SD_BUS_DEFAULT_SYSTEM:
+                return default_system_bus;
+        default:
+                return bus;
+        }
+}
+
 void bus_close_io_fds(sd_bus *b) {
         assert(b);
 
@@ -224,6 +282,7 @@ _public_ int sd_bus_set_address(sd_bus *bus, const char *address) {
         char *a;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(bus->state == BUS_UNSET, -EPERM);
         assert_return(address, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
@@ -240,6 +299,7 @@ _public_ int sd_bus_set_address(sd_bus *bus, const char *address) {
 
 _public_ int sd_bus_set_fd(sd_bus *bus, int input_fd, int output_fd) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(bus->state == BUS_UNSET, -EPERM);
         assert_return(input_fd >= 0, -EBADF);
         assert_return(output_fd >= 0, -EBADF);
@@ -254,6 +314,7 @@ _public_ int sd_bus_set_exec(sd_bus *bus, const char *path, char *const argv[])
         char *p, **a;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(bus->state == BUS_UNSET, -EPERM);
         assert_return(path, -EINVAL);
         assert_return(!strv_isempty(argv), -EINVAL);
@@ -280,6 +341,7 @@ _public_ int sd_bus_set_exec(sd_bus *bus, const char *path, char *const argv[])
 
 _public_ int sd_bus_set_bus_client(sd_bus *bus, int b) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(bus->state == BUS_UNSET, -EPERM);
         assert_return(!bus->patch_sender, -EPERM);
         assert_return(!bus_pid_changed(bus), -ECHILD);
@@ -290,6 +352,7 @@ _public_ int sd_bus_set_bus_client(sd_bus *bus, int b) {
 
 _public_ int sd_bus_set_monitor(sd_bus *bus, int b) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(bus->state == BUS_UNSET, -EPERM);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -299,6 +362,7 @@ _public_ int sd_bus_set_monitor(sd_bus *bus, int b) {
 
 _public_ int sd_bus_negotiate_fds(sd_bus *bus, int b) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(bus->state == BUS_UNSET, -EPERM);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -308,6 +372,7 @@ _public_ int sd_bus_negotiate_fds(sd_bus *bus, int b) {
 
 _public_ int sd_bus_negotiate_timestamp(sd_bus *bus, int b) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!IN_SET(bus->state, BUS_CLOSING, BUS_CLOSED), -EPERM);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -320,6 +385,7 @@ _public_ int sd_bus_negotiate_timestamp(sd_bus *bus, int b) {
 
 _public_ int sd_bus_negotiate_creds(sd_bus *bus, int b, uint64_t mask) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(mask <= _SD_BUS_CREDS_ALL, -EINVAL);
         assert_return(!IN_SET(bus->state, BUS_CLOSING, BUS_CLOSED), -EPERM);
         assert_return(!bus_pid_changed(bus), -ECHILD);
@@ -334,6 +400,7 @@ _public_ int sd_bus_negotiate_creds(sd_bus *bus, int b, uint64_t mask) {
 
 _public_ int sd_bus_set_server(sd_bus *bus, int b, sd_id128_t server_id) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(b || sd_id128_equal(server_id, SD_ID128_NULL), -EINVAL);
         assert_return(bus->state == BUS_UNSET, -EPERM);
         assert_return(!bus_pid_changed(bus), -ECHILD);
@@ -345,6 +412,7 @@ _public_ int sd_bus_set_server(sd_bus *bus, int b, sd_id128_t server_id) {
 
 _public_ int sd_bus_set_anonymous(sd_bus *bus, int b) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(bus->state == BUS_UNSET, -EPERM);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -354,6 +422,7 @@ _public_ int sd_bus_set_anonymous(sd_bus *bus, int b) {
 
 _public_ int sd_bus_set_trusted(sd_bus *bus, int b) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(bus->state == BUS_UNSET, -EPERM);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -363,6 +432,7 @@ _public_ int sd_bus_set_trusted(sd_bus *bus, int b) {
 
 _public_ int sd_bus_set_description(sd_bus *bus, const char *description) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(bus->state == BUS_UNSET, -EPERM);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -371,6 +441,7 @@ _public_ int sd_bus_set_description(sd_bus *bus, const char *description) {
 
 _public_ int sd_bus_set_allow_interactive_authorization(sd_bus *bus, int b) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         bus->allow_interactive_authorization = !!b;
@@ -379,6 +450,7 @@ _public_ int sd_bus_set_allow_interactive_authorization(sd_bus *bus, int b) {
 
 _public_ int sd_bus_get_allow_interactive_authorization(sd_bus *bus) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         return bus->allow_interactive_authorization;
@@ -386,6 +458,7 @@ _public_ int sd_bus_get_allow_interactive_authorization(sd_bus *bus) {
 
 _public_ int sd_bus_set_watch_bind(sd_bus *bus, int b) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(bus->state == BUS_UNSET, -EPERM);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -395,6 +468,7 @@ _public_ int sd_bus_set_watch_bind(sd_bus *bus, int b) {
 
 _public_ int sd_bus_get_watch_bind(sd_bus *bus) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         return bus->watch_bind;
@@ -402,6 +476,7 @@ _public_ int sd_bus_get_watch_bind(sd_bus *bus) {
 
 _public_ int sd_bus_set_connected_signal(sd_bus *bus, int b) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(bus->state == BUS_UNSET, -EPERM);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -411,6 +486,7 @@ _public_ int sd_bus_set_connected_signal(sd_bus *bus, int b) {
 
 _public_ int sd_bus_get_connected_signal(sd_bus *bus) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         return bus->connected_signal;
@@ -1118,6 +1194,7 @@ _public_ int sd_bus_start(sd_bus *bus) {
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(bus->state == BUS_UNSET, -EPERM);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -1503,6 +1580,7 @@ _public_ sd_bus *sd_bus_unref(sd_bus *bus) {
 _public_ int sd_bus_is_open(sd_bus *bus) {
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         return BUS_IS_OPEN(bus->state);
@@ -1510,6 +1588,7 @@ _public_ int sd_bus_is_open(sd_bus *bus) {
 
 _public_ int sd_bus_is_ready(sd_bus *bus) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         return bus->state == BUS_RUNNING;
@@ -1519,6 +1598,7 @@ _public_ int sd_bus_can_send(sd_bus *bus, char type) {
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(bus->state != BUS_UNSET, -ENOTCONN);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -1543,6 +1623,7 @@ _public_ int sd_bus_get_bus_id(sd_bus *bus, sd_id128_t *id) {
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(id, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -2143,6 +2224,7 @@ fail:
 _public_ int sd_bus_get_fd(sd_bus *bus) {
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(bus->input_fd == bus->output_fd, -EPERM);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -2162,6 +2244,7 @@ _public_ int sd_bus_get_events(sd_bus *bus) {
         int flags = 0;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         switch (bus->state) {
@@ -2207,6 +2290,7 @@ _public_ int sd_bus_get_timeout(sd_bus *bus, uint64_t *timeout_usec) {
         struct reply_callback *c;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(timeout_usec, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -2848,6 +2932,7 @@ static int bus_process_internal(sd_bus *bus, bool hint_priority, int64_t priorit
          * means *ret is filled in with an unprocessed message. */
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         /* We don't allow recursively invoking sd_bus_process(). */
@@ -2979,6 +3064,7 @@ static int bus_poll(sd_bus *bus, bool need_more, uint64_t timeout_usec) {
 _public_ int sd_bus_wait(sd_bus *bus, uint64_t timeout_usec) {
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         if (bus->state == BUS_CLOSING)
@@ -2997,6 +3083,7 @@ _public_ int sd_bus_flush(sd_bus *bus) {
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         if (bus->state == BUS_CLOSING)
@@ -3045,6 +3132,7 @@ _public_ int sd_bus_add_filter(
         sd_bus_slot *s;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(callback, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -3143,6 +3231,7 @@ static int bus_add_match_full(
         int r = 0;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(match, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -3443,6 +3532,7 @@ _public_ int sd_bus_attach_event(sd_bus *bus, sd_event *event, int priority) {
         int r;
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus->event, -EBUSY);
 
         assert(!bus->input_io_event_source);
@@ -3496,6 +3586,7 @@ fail:
 
 _public_ int sd_bus_detach_event(sd_bus *bus) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
 
         if (!bus->event)
                 return 0;
@@ -3588,40 +3679,16 @@ _public_ int sd_bus_default_user(sd_bus **ret) {
 }
 
 _public_ int sd_bus_default(sd_bus **ret) {
+        int (*bus_open)(sd_bus **) = NULL;
+        sd_bus **busp;
 
-        const char *e;
-
-        /* Let's try our best to reuse another cached connection. If
-         * the starter bus type is set, connect via our normal
-         * connection logic, ignoring $DBUS_STARTER_ADDRESS, so that
-         * we can share the connection with the user/system default
-         * bus. */
-
-        e = secure_getenv("DBUS_STARTER_BUS_TYPE");
-        if (e) {
-                if (streq(e, "system"))
-                        return sd_bus_default_system(ret);
 #if 0 /// elogind does not support systemd units
-                else if (STR_IN_SET(e, "user", "session"))
-                        return sd_bus_default_user(ret);
 #endif // 0
-        }
-
-        /* No type is specified, so we have not other option than to
-         * use the starter address if it is set. */
-        e = secure_getenv("DBUS_STARTER_ADDRESS");
-        if (e)
-                return bus_default(sd_bus_open, &default_starter_bus, ret);
-
-        /* Finally, if nothing is set use the cached connection for
-         * the right scope */
 
 #if 0 /// elogind does not support systemd user instances
-        if (cg_pid_get_owner_uid(0, NULL) >= 0)
-                return sd_bus_default_user(ret);
-        else
 #endif // 0
-                return sd_bus_default_system(ret);
+        busp = bus_choose_default(&bus_open);
+        return bus_default(bus_open, busp, ret);
 }
 
 _public_ int sd_bus_get_tid(sd_bus *b, pid_t *tid) {
@@ -3848,6 +3915,7 @@ _public_ int sd_bus_path_decode_many(const char *path, const char *path_template
 
 _public_ int sd_bus_try_close(sd_bus *bus) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         return -EOPNOTSUPP;
@@ -3855,6 +3923,7 @@ _public_ int sd_bus_try_close(sd_bus *bus) {
 
 _public_ int sd_bus_get_description(sd_bus *bus, const char **description) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(description, -EINVAL);
         assert_return(bus->description, -ENXIO);
         assert_return(!bus_pid_changed(bus), -ECHILD);
@@ -3883,6 +3952,7 @@ int bus_get_root_path(sd_bus *bus) {
 
 _public_ int sd_bus_get_scope(sd_bus *bus, const char **scope) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(scope, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -3902,6 +3972,7 @@ _public_ int sd_bus_get_scope(sd_bus *bus, const char **scope) {
 _public_ int sd_bus_get_address(sd_bus *bus, const char **address) {
 
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(address, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -3915,6 +3986,7 @@ _public_ int sd_bus_get_address(sd_bus *bus, const char **address) {
 
 _public_ int sd_bus_get_creds_mask(sd_bus *bus, uint64_t *mask) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(mask, -EINVAL);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
@@ -3924,6 +3996,7 @@ _public_ int sd_bus_get_creds_mask(sd_bus *bus, uint64_t *mask) {
 
 _public_ int sd_bus_is_bus_client(sd_bus *bus) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         return bus->bus_client;
@@ -3931,6 +4004,7 @@ _public_ int sd_bus_is_bus_client(sd_bus *bus) {
 
 _public_ int sd_bus_is_server(sd_bus *bus) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         return bus->is_server;
@@ -3938,6 +4012,7 @@ _public_ int sd_bus_is_server(sd_bus *bus) {
 
 _public_ int sd_bus_is_anonymous(sd_bus *bus) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         return bus->anonymous_auth;
@@ -3945,6 +4020,7 @@ _public_ int sd_bus_is_anonymous(sd_bus *bus) {
 
 _public_ int sd_bus_is_trusted(sd_bus *bus) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         return bus->trusted;
@@ -3952,6 +4028,7 @@ _public_ int sd_bus_is_trusted(sd_bus *bus) {
 
 _public_ int sd_bus_is_monitor(sd_bus *bus) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
         return bus->is_monitor;
@@ -3978,6 +4055,7 @@ _public_ void sd_bus_default_flush_close(void) {
 
 _public_ int sd_bus_set_exit_on_disconnect(sd_bus *bus, int b) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
 
         /* Turns on exit-on-disconnect, and triggers it immediately if the bus connection was already
          * disconnected. Note that this is triggered exclusively on disconnections triggered by the server side, never
@@ -3990,12 +4068,14 @@ _public_ int sd_bus_set_exit_on_disconnect(sd_bus *bus, int b) {
 
 _public_ int sd_bus_get_exit_on_disconnect(sd_bus *bus) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
 
         return bus->exit_on_disconnect;
 }
 
 _public_ int sd_bus_set_sender(sd_bus *bus, const char *sender) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(!bus->bus_client, -EPERM);
         assert_return(!sender || service_name_is_valid(sender), -EINVAL);
 
@@ -4004,6 +4084,7 @@ _public_ int sd_bus_set_sender(sd_bus *bus, const char *sender) {
 
 _public_ int sd_bus_get_sender(sd_bus *bus, const char **ret) {
         assert_return(bus, -EINVAL);
+        assert_return(bus = bus_resolve(bus), -ENOPKG);
         assert_return(ret, -EINVAL);
 
         if (!bus->patch_sender)
diff --git a/src/systemd/sd-bus.h b/src/systemd/sd-bus.h
index d15278555..e17d17683 100644
--- a/src/systemd/sd-bus.h
+++ b/src/systemd/sd-bus.h
@@ -33,6 +33,10 @@
 
 _SD_BEGIN_DECLARATIONS;
 
+#define SD_BUS_DEFAULT ((sd_bus *) 1)
+#define SD_BUS_DEFAULT_USER ((sd_bus *) 2)
+#define SD_BUS_DEFAULT_SYSTEM ((sd_bus *) 3)
+
 /* Types */
 
 typedef struct sd_bus sd_bus;