Revert "sd-bus: do not connect to dbus-1 socket when kdbus is available"

This reverts commit d4d00020d6ad855d65d31020fefa5003e1bb477f. The idea of
the commit is broken and needs to be reworked. We really cannot reduce
the bus-addresses to a single address. We always will have systemd with
native clients and legacy clients at the same time, so we also need both
addresses at the same time.

31 files changed, 98 insertions, 95 deletions

diff --git a/src/basic/def.h b/src/basic/def.h
index e0d6822f38..5aaba1fe87 100644
--- a/src/basic/def.h
+++ b/src/basic/def.h
@@ -63,6 +63,7 @@
 
 #define UNIX_SYSTEM_BUS_ADDRESS "unix:path=/var/run/dbus/system_bus_socket"
 #define KERNEL_SYSTEM_BUS_ADDRESS "kernel:path=/sys/fs/kdbus/0-system/bus"
+#define DEFAULT_SYSTEM_BUS_ADDRESS KERNEL_SYSTEM_BUS_ADDRESS ";" UNIX_SYSTEM_BUS_ADDRESS
 #define UNIX_USER_BUS_ADDRESS_FMT "unix:path=%s/bus"
 #define KERNEL_USER_BUS_ADDRESS_FMT "kernel:path=/sys/fs/kdbus/"UID_FMT"-user/bus"
 
diff --git a/src/bus-proxyd/bus-proxyd.c b/src/bus-proxyd/bus-proxyd.c
index 6e07aea94e..3cc3b33ae7 100644
--- a/src/bus-proxyd/bus-proxyd.c
+++ b/src/bus-proxyd/bus-proxyd.c
@@ -177,9 +177,8 @@ static int help(void) {
                "     --configuration=PATH Configuration file or directory\n"
                "     --machine=MACHINE    Connect to specified machine\n"
                "     --address=ADDRESS    Connect to the bus specified by ADDRESS\n"
-               "                          (default: %s)\n",
-               program_invocation_short_name,
-               is_kdbus_available() ? KERNEL_SYSTEM_BUS_ADDRESS : UNIX_SYSTEM_BUS_ADDRESS);
+               "                          (default: " DEFAULT_SYSTEM_BUS_ADDRESS ")\n",
+               program_invocation_short_name);
 
         return 0;
 }
@@ -263,7 +262,7 @@ static int parse_argv(int argc, char *argv[]) {
         }
 
         if (!arg_address) {
-                arg_address = strdup(is_kdbus_available() ? KERNEL_SYSTEM_BUS_ADDRESS : UNIX_SYSTEM_BUS_ADDRESS);
+                arg_address = strdup(DEFAULT_SYSTEM_BUS_ADDRESS);
                 if (!arg_address)
                         return log_oom();
         }
diff --git a/src/bus-proxyd/stdio-bridge.c b/src/bus-proxyd/stdio-bridge.c
index c5dac396d3..f275f6705f 100644
--- a/src/bus-proxyd/stdio-bridge.c
+++ b/src/bus-proxyd/stdio-bridge.c
@@ -50,9 +50,8 @@ static int help(void) {
                "     --version            Show package version\n"
                "     --machine=MACHINE    Connect to specified machine\n"
                "     --address=ADDRESS    Connect to the bus specified by ADDRESS\n"
-               "                          (default: %s)\n",
-               program_invocation_short_name,
-               is_kdbus_available() ? KERNEL_SYSTEM_BUS_ADDRESS : UNIX_SYSTEM_BUS_ADDRESS);
+               "                          (default: " DEFAULT_SYSTEM_BUS_ADDRESS ")\n",
+               program_invocation_short_name);
 
         return 0;
 }
@@ -138,7 +137,7 @@ static int parse_argv(int argc, char *argv[]) {
         }
 
         if (!arg_address) {
-                arg_address = strdup(is_kdbus_available() ? KERNEL_SYSTEM_BUS_ADDRESS : UNIX_SYSTEM_BUS_ADDRESS);
+                arg_address = strdup(DEFAULT_SYSTEM_BUS_ADDRESS);
                 if (!arg_address)
                         return log_oom();
         }
diff --git a/src/core/automount.c b/src/core/automount.c
index 2b84c441b2..4af381b4b6 100644
--- a/src/core/automount.c
+++ b/src/core/automount.c
@@ -39,6 +39,7 @@
 #include "path-util.h"
 #include "dbus-automount.h"
 #include "bus-util.h"
+#include "bus-error.h"
 #include "formats-util.h"
 #include "process-util.h"
 #include "async.h"
diff --git a/src/core/service.c b/src/core/service.c
index 7bd8cb8b91..b790ec98be 100644
--- a/src/core/service.c
+++ b/src/core/service.c
@@ -42,6 +42,7 @@
 #include "utf8.h"
 #include "env-util.h"
 #include "fileio.h"
+#include "bus-error.h"
 #include "bus-util.h"
 #include "bus-kernel.h"
 #include "formats-util.h"
diff --git a/src/core/socket.c b/src/core/socket.c
index c78e8ad01b..a387057473 100644
--- a/src/core/socket.c
+++ b/src/core/socket.c
@@ -43,6 +43,7 @@
 #include "def.h"
 #include "smack-util.h"
 #include "bus-util.h"
+#include "bus-error.h"
 #include "selinux-util.h"
 #include "dbus-socket.h"
 #include "unit.h"
diff --git a/src/core/timer.c b/src/core/timer.c
index 7027f83dfd..89758c6b19 100644
--- a/src/core/timer.c
+++ b/src/core/timer.c
@@ -27,6 +27,7 @@
 #include "dbus-timer.h"
 #include "special.h"
 #include "bus-util.h"
+#include "bus-error.h"
 
 static const UnitActiveState state_translation_table[_TIMER_STATE_MAX] = {
         [TIMER_DEAD] = UNIT_INACTIVE,
diff --git a/src/dbus1-generator/dbus1-generator.c b/src/dbus1-generator/dbus1-generator.c
index 25c8e209fd..4980fccc31 100644
--- a/src/dbus1-generator/dbus1-generator.c
+++ b/src/dbus1-generator/dbus1-generator.c
@@ -84,8 +84,7 @@ static int create_dbus_files(
                         fprintf(f, "Environment=DBUS_STARTER_BUS_TYPE=%s\n", type);
 
                         if (streq(type, "system"))
-                                fprintf(f, "Environment=DBUS_STARTER_ADDRESS=%s\n",
-                                        is_kdbus_available() ? KERNEL_SYSTEM_BUS_ADDRESS : UNIX_SYSTEM_BUS_ADDRESS);
+                                fprintf(f, "Environment=DBUS_STARTER_ADDRESS=" DEFAULT_SYSTEM_BUS_ADDRESS "\n");
                         else if (streq(type, "session")) {
                                 char *run;
 
@@ -95,10 +94,8 @@ static int create_dbus_files(
                                         return -EINVAL;
                                 }
 
-                                if (is_kdbus_available())
-                                        fprintf(f, "Environment=DBUS_STARTER_ADDRESS="KERNEL_USER_BUS_ADDRESS_FMT "\n", getuid());
-                                else
-                                        fprintf(f, "Environment=DBUS_STARTER_ADDRESS="UNIX_USER_BUS_ADDRESS_FMT "\n", run);
+                                fprintf(f, "Environment=DBUS_STARTER_ADDRESS="KERNEL_USER_BUS_ADDRESS_FMT ";" UNIX_USER_BUS_ADDRESS_FMT "\n",
+                                        getuid(), run);
                         }
                 }
 
diff --git a/src/libsystemd/sd-bus/bus-control.c b/src/libsystemd/sd-bus/bus-control.c
index ef3e087b28..aeb48bedd1 100644
--- a/src/libsystemd/sd-bus/bus-control.c
+++ b/src/libsystemd/sd-bus/bus-control.c
@@ -32,6 +32,7 @@
 #include "bus-message.h"
 #include "bus-control.h"
 #include "bus-bloom.h"
+#include "bus-util.h"
 #include "capability.h"
 
 _public_ int sd_bus_get_unique_name(sd_bus *bus, const char **unique) {
diff --git a/src/libsystemd/sd-bus/bus-convenience.c b/src/libsystemd/sd-bus/bus-convenience.c
index 79747e058b..af5f7da11c 100644
--- a/src/libsystemd/sd-bus/bus-convenience.c
+++ b/src/libsystemd/sd-bus/bus-convenience.c
@@ -22,6 +22,7 @@
 #include "bus-internal.h"
 #include "bus-message.h"
 #include "bus-signature.h"
+#include "bus-util.h"
 #include "bus-type.h"
 
 _public_ int sd_bus_emit_signal(
diff --git a/src/libsystemd/sd-bus/bus-creds.c b/src/libsystemd/sd-bus/bus-creds.c
index 130fbf7a23..1c365b7fcd 100644
--- a/src/libsystemd/sd-bus/bus-creds.c
+++ b/src/libsystemd/sd-bus/bus-creds.c
@@ -31,10 +31,10 @@
 #include "fileio.h"
 #include "audit.h"
 #include "bus-message.h"
+#include "bus-util.h"
 #include "strv.h"
 #include "bus-creds.h"
 #include "bus-label.h"
-#include "bus-internal.h"
 
 enum {
         CAP_OFFSET_INHERITABLE = 0,
diff --git a/src/libsystemd/sd-bus/bus-internal.c b/src/libsystemd/sd-bus/bus-internal.c
index f4ab57f5bc..fea796cd30 100644
--- a/src/libsystemd/sd-bus/bus-internal.c
+++ b/src/libsystemd/sd-bus/bus-internal.c
@@ -371,45 +371,3 @@ int bus_maybe_reply_error(sd_bus_message *m, int r, sd_bus_error *error) {
 
         return 1;
 }
-
-bool is_kdbus_wanted(void) {
-        _cleanup_free_ char *value = NULL;
-#ifdef ENABLE_KDBUS
-        const bool configured = true;
-#else
-        const bool configured = false;
-#endif
-        int r;
-
-        if (get_proc_cmdline_key("kdbus", NULL) > 0)
-                return true;
-
-        r = get_proc_cmdline_key("kdbus=", &value);
-        if (r <= 0)
-                return configured;
-
-        return parse_boolean(value) == 1;
-}
-
-bool is_kdbus_available(void) {
-        static int cached = -1;
-        _cleanup_close_ int fd = -1;
-        struct kdbus_cmd cmd = { .size = sizeof(cmd), .flags = KDBUS_FLAG_NEGOTIATE };
-
-        if (cached >= 0)
-                return (bool) cached;
-
-        if (!is_kdbus_wanted()) {
-                cached = false;
-                return false;
-        }
-
-        fd = open("/sys/fs/kdbus/control", O_RDWR | O_CLOEXEC | O_NONBLOCK | O_NOCTTY);
-        if (fd < 0) {
-                cached = false;
-                return false;
-        }
-
-        cached = ioctl(fd, KDBUS_CMD_BUS_MAKE, &cmd) >= 0;
-        return cached;
-}
diff --git a/src/libsystemd/sd-bus/bus-internal.h b/src/libsystemd/sd-bus/bus-internal.h
index 9b68fdd642..7af61a9433 100644
--- a/src/libsystemd/sd-bus/bus-internal.h
+++ b/src/libsystemd/sd-bus/bus-internal.h
@@ -37,29 +37,6 @@
 #include "bus-kernel.h"
 #include "kdbus.h"
 
-typedef enum BusTransport {
-        BUS_TRANSPORT_LOCAL,
-        BUS_TRANSPORT_REMOTE,
-        BUS_TRANSPORT_MACHINE,
-        _BUS_TRANSPORT_MAX,
-        _BUS_TRANSPORT_INVALID = -1
-} BusTransport;
-
-DEFINE_TRIVIAL_CLEANUP_FUNC(sd_bus*, sd_bus_unref);
-DEFINE_TRIVIAL_CLEANUP_FUNC(sd_bus*, sd_bus_flush_close_unref);
-DEFINE_TRIVIAL_CLEANUP_FUNC(sd_bus_slot*, sd_bus_slot_unref);
-DEFINE_TRIVIAL_CLEANUP_FUNC(sd_bus_message*, sd_bus_message_unref);
-DEFINE_TRIVIAL_CLEANUP_FUNC(sd_bus_creds*, sd_bus_creds_unref);
-DEFINE_TRIVIAL_CLEANUP_FUNC(sd_bus_track*, sd_bus_track_unref);
-
-#define _cleanup_bus_unref_ _cleanup_(sd_bus_unrefp)
-#define _cleanup_bus_flush_close_unref_ _cleanup_(sd_bus_flush_close_unrefp)
-#define _cleanup_bus_slot_unref_ _cleanup_(sd_bus_slot_unrefp)
-#define _cleanup_bus_message_unref_ _cleanup_(sd_bus_message_unrefp)
-#define _cleanup_bus_creds_unref_ _cleanup_(sd_bus_creds_unrefp)
-#define _cleanup_bus_track_unref_ _cleanup_(sd_bus_slot_unrefp)
-#define _cleanup_bus_error_free_ _cleanup_(sd_bus_error_free)
-
 struct reply_callback {
         sd_bus_message_handler_t callback;
         usec_t timeout;
@@ -417,9 +394,6 @@ int bus_get_root_path(sd_bus *bus);
 
 int bus_maybe_reply_error(sd_bus_message *m, int r, sd_bus_error *error);
 
-bool is_kdbus_wanted(void);
-bool is_kdbus_available(void);
-
 #define bus_assert_return(expr, r, error)                               \
         do {                                                            \
                 if (!assert_log(expr))                                  \
diff --git a/src/libsystemd/sd-bus/bus-kernel.c b/src/libsystemd/sd-bus/bus-kernel.c
index 6750cbd77b..577a8b44c3 100644
--- a/src/libsystemd/sd-bus/bus-kernel.c
+++ b/src/libsystemd/sd-bus/bus-kernel.c
@@ -45,6 +45,7 @@
 #include "bus-message.h"
 #include "bus-kernel.h"
 #include "bus-bloom.h"
+#include "bus-util.h"
 #include "bus-label.h"
 
 #define UNIQUE_NAME_MAX (3+DECIMAL_STR_MAX(uint64_t))
diff --git a/src/libsystemd/sd-bus/bus-match.c b/src/libsystemd/sd-bus/bus-match.c
index 7175cbe8ed..2b83f439a7 100644
--- a/src/libsystemd/sd-bus/bus-match.c
+++ b/src/libsystemd/sd-bus/bus-match.c
@@ -22,6 +22,7 @@
 #include "bus-internal.h"
 #include "bus-message.h"
 #include "bus-match.h"
+#include "bus-util.h"
 #include "strv.h"
 
 /* Example:
diff --git a/src/libsystemd/sd-bus/bus-message.c b/src/libsystemd/sd-bus/bus-message.c
index 970aaabdc2..a21ed8cb62 100644
--- a/src/libsystemd/sd-bus/bus-message.c
+++ b/src/libsystemd/sd-bus/bus-message.c
@@ -35,6 +35,7 @@
 #include "bus-type.h"
 #include "bus-signature.h"
 #include "bus-gvariant.h"
+#include "bus-util.h"
 
 static int message_append_basic(sd_bus_message *m, char type, const void *p, const void **stored);
 
diff --git a/src/libsystemd/sd-bus/bus-objects.c b/src/libsystemd/sd-bus/bus-objects.c
index a8e9a12494..0593aa658a 100644
--- a/src/libsystemd/sd-bus/bus-objects.c
+++ b/src/libsystemd/sd-bus/bus-objects.c
@@ -26,6 +26,7 @@
 #include "bus-type.h"
 #include "bus-signature.h"
 #include "bus-introspect.h"
+#include "bus-util.h"
 #include "bus-slot.h"
 #include "bus-objects.h"
 
diff --git a/src/libsystemd/sd-bus/bus-track.c b/src/libsystemd/sd-bus/bus-track.c
index 7803e39c3d..e43891be25 100644
--- a/src/libsystemd/sd-bus/bus-track.c
+++ b/src/libsystemd/sd-bus/bus-track.c
@@ -20,6 +20,7 @@
 ***/
 
 #include "sd-bus.h"
+#include "bus-util.h"
 #include "bus-internal.h"
 #include "bus-track.h"
 
diff --git a/src/libsystemd/sd-bus/busctl.c b/src/libsystemd/sd-bus/busctl.c
index 181621ffc7..a1f0f30d6c 100644
--- a/src/libsystemd/sd-bus/busctl.c
+++ b/src/libsystemd/sd-bus/busctl.c
@@ -30,6 +30,7 @@
 #include "set.h"
 
 #include "sd-bus.h"
+#include "bus-internal.h"
 #include "bus-util.h"
 #include "bus-dump.h"
 #include "bus-signature.h"
diff --git a/src/libsystemd/sd-bus/sd-bus.c b/src/libsystemd/sd-bus/sd-bus.c
index 31cdcb4e5b..5434d62af5 100644
--- a/src/libsystemd/sd-bus/sd-bus.c
+++ b/src/libsystemd/sd-bus/sd-bus.c
@@ -44,6 +44,7 @@
 #include "bus-kernel.h"
 #include "bus-control.h"
 #include "bus-objects.h"
+#include "bus-util.h"
 #include "bus-container.h"
 #include "bus-protocol.h"
 #include "bus-track.h"
@@ -1173,10 +1174,7 @@ int bus_set_address_system(sd_bus *b) {
         if (e)
                 return sd_bus_set_address(b, e);
 
-        if (is_kdbus_available())
-                return sd_bus_set_address(b, KERNEL_SYSTEM_BUS_ADDRESS);
-
-        return sd_bus_set_address(b, UNIX_SYSTEM_BUS_ADDRESS);
+        return sd_bus_set_address(b, DEFAULT_SYSTEM_BUS_ADDRESS);
 }
 
 _public_ int sd_bus_open_system(sd_bus **ret) {
@@ -1224,17 +1222,16 @@ int bus_set_address_user(sd_bus *b) {
                 return sd_bus_set_address(b, e);
 
         e = secure_getenv("XDG_RUNTIME_DIR");
-        if (is_kdbus_available())
-                (void) asprintf(&b->address, KERNEL_USER_BUS_ADDRESS_FMT, getuid());
-        else if (e) {
+        if (e) {
                 _cleanup_free_ char *ee = NULL;
 
                 ee = bus_address_escape(e);
                 if (!ee)
                         return -ENOMEM;
 
-                (void) asprintf(&b->address, UNIX_USER_BUS_ADDRESS_FMT, ee);
-        }
+                (void) asprintf(&b->address, KERNEL_USER_BUS_ADDRESS_FMT ";" UNIX_USER_BUS_ADDRESS_FMT, getuid(), ee);
+        } else
+                (void) asprintf(&b->address, KERNEL_USER_BUS_ADDRESS_FMT, getuid());
 
         if (!b->address)
                 return -ENOMEM;
diff --git a/src/libsystemd/sd-bus/test-bus-benchmark.c b/src/libsystemd/sd-bus/test-bus-benchmark.c
index d3bf6da850..d14110aa04 100644
--- a/src/libsystemd/sd-bus/test-bus-benchmark.c
+++ b/src/libsystemd/sd-bus/test-bus-benchmark.c
@@ -28,6 +28,7 @@
 #include "sd-bus.h"
 #include "bus-kernel.h"
 #include "bus-internal.h"
+#include "bus-util.h"
 
 #define MAX_SIZE (2*1024*1024)
 
diff --git a/src/libsystemd/sd-bus/test-bus-chat.c b/src/libsystemd/sd-bus/test-bus-chat.c
index a0aecc1f55..20f1b532b7 100644
--- a/src/libsystemd/sd-bus/test-bus-chat.c
+++ b/src/libsystemd/sd-bus/test-bus-chat.c
@@ -33,6 +33,7 @@
 #include "bus-error.h"
 #include "bus-match.h"
 #include "bus-internal.h"
+#include "bus-util.h"
 
 static int match_callback(sd_bus_message *m, void *userdata, sd_bus_error *ret_error) {
         log_info("Match triggered! interface=%s member=%s", strna(sd_bus_message_get_interface(m)), strna(sd_bus_message_get_member(m)));
diff --git a/src/libsystemd/sd-bus/test-bus-cleanup.c b/src/libsystemd/sd-bus/test-bus-cleanup.c
index b483d47468..f586880593 100644
--- a/src/libsystemd/sd-bus/test-bus-cleanup.c
+++ b/src/libsystemd/sd-bus/test-bus-cleanup.c
@@ -22,6 +22,7 @@
 #include <stdio.h>
 
 #include "sd-bus.h"
+#include "bus-util.h"
 #include "bus-internal.h"
 #include "bus-message.h"
 #include "refcnt.h"
diff --git a/src/libsystemd/sd-bus/test-bus-error.c b/src/libsystemd/sd-bus/test-bus-error.c
index f2cfbc706f..5753c04b0e 100644
--- a/src/libsystemd/sd-bus/test-bus-error.c
+++ b/src/libsystemd/sd-bus/test-bus-error.c
@@ -20,6 +20,7 @@
 ***/
 
 #include "sd-bus.h"
+#include "bus-error.h"
 #include "bus-util.h"
 #include "errno-list.h"
 #include "bus-common-errors.h"
diff --git a/src/libsystemd/sd-bus/test-bus-gvariant.c b/src/libsystemd/sd-bus/test-bus-gvariant.c
index 414d4e9a58..b078bdc5f6 100644
--- a/src/libsystemd/sd-bus/test-bus-gvariant.c
+++ b/src/libsystemd/sd-bus/test-bus-gvariant.c
@@ -27,6 +27,7 @@
 #include "macro.h"
 #include "sd-bus.h"
 #include "bus-gvariant.h"
+#include "bus-util.h"
 #include "bus-internal.h"
 #include "bus-message.h"
 #include "bus-dump.h"
diff --git a/src/libsystemd/sd-bus/test-bus-kernel.c b/src/libsystemd/sd-bus/test-bus-kernel.c
index 6284153a58..6506eaab2e 100644
--- a/src/libsystemd/sd-bus/test-bus-kernel.c
+++ b/src/libsystemd/sd-bus/test-bus-kernel.c
@@ -25,8 +25,8 @@
 #include "log.h"
 
 #include "sd-bus.h"
-#include "bus-util.h"
 #include "bus-kernel.h"
+#include "bus-util.h"
 #include "bus-dump.h"
 
 int main(int argc, char *argv[]) {
diff --git a/src/libsystemd/sd-bus/test-bus-match.c b/src/libsystemd/sd-bus/test-bus-match.c
index e29975db44..75ea28371b 100644
--- a/src/libsystemd/sd-bus/test-bus-match.c
+++ b/src/libsystemd/sd-bus/test-bus-match.c
@@ -24,6 +24,7 @@
 
 #include "bus-match.h"
 #include "bus-message.h"
+#include "bus-util.h"
 #include "bus-slot.h"
 
 static bool mask[32];
diff --git a/src/libsystemd/sd-bus/test-bus-objects.c b/src/libsystemd/sd-bus/test-bus-objects.c
index 195013f49a..0a35b750b3 100644
--- a/src/libsystemd/sd-bus/test-bus-objects.c
+++ b/src/libsystemd/sd-bus/test-bus-objects.c
@@ -30,6 +30,7 @@
 #include "sd-bus.h"
 #include "bus-internal.h"
 #include "bus-message.h"
+#include "bus-util.h"
 #include "bus-dump.h"
 
 struct context {
diff --git a/src/libsystemd/sd-bus/test-bus-server.c b/src/libsystemd/sd-bus/test-bus-server.c
index 604df098cc..080d8eddb7 100644
--- a/src/libsystemd/sd-bus/test-bus-server.c
+++ b/src/libsystemd/sd-bus/test-bus-server.c
@@ -28,6 +28,7 @@
 
 #include "sd-bus.h"
 #include "bus-internal.h"
+#include "bus-util.h"
 
 struct context {
         int fds[2];
diff --git a/src/shared/bus-util.c b/src/shared/bus-util.c
index 1bcb8903f3..1369a61458 100644
--- a/src/shared/bus-util.c
+++ b/src/shared/bus-util.c
@@ -2032,3 +2032,37 @@ int bus_path_decode_unique(const char *path, const char *prefix, char **ret_send
         *ret_external = external;
         return 1;
 }
+
+bool is_kdbus_wanted(void) {
+        _cleanup_free_ char *value = NULL;
+#ifdef ENABLE_KDBUS
+        const bool configured = true;
+#else
+        const bool configured = false;
+#endif
+
+        int r;
+
+        if (get_proc_cmdline_key("kdbus", NULL) > 0)
+                return true;
+
+        r = get_proc_cmdline_key("kdbus=", &value);
+        if (r <= 0)
+                return configured;
+
+        return parse_boolean(value) == 1;
+}
+
+bool is_kdbus_available(void) {
+        _cleanup_close_ int fd = -1;
+        struct kdbus_cmd cmd = { .size = sizeof(cmd), .flags = KDBUS_FLAG_NEGOTIATE };
+
+        if (!is_kdbus_wanted())
+                return false;
+
+        fd = open("/sys/fs/kdbus/control", O_RDWR | O_CLOEXEC | O_NONBLOCK | O_NOCTTY);
+        if (fd < 0)
+                return false;
+
+        return ioctl(fd, KDBUS_CMD_BUS_MAKE, &cmd) >= 0;
+}
diff --git a/src/shared/bus-util.h b/src/shared/bus-util.h
index 0c683c0713..4ae216b7d9 100644
--- a/src/shared/bus-util.h
+++ b/src/shared/bus-util.h
@@ -23,12 +23,18 @@
 
 #include "sd-event.h"
 #include "sd-bus.h"
-#include "bus-error.h"
-#include "bus-internal.h"
 #include "hashmap.h"
 #include "install.h"
 #include "time-util.h"
 
+typedef enum BusTransport {
+        BUS_TRANSPORT_LOCAL,
+        BUS_TRANSPORT_REMOTE,
+        BUS_TRANSPORT_MACHINE,
+        _BUS_TRANSPORT_MAX,
+        _BUS_TRANSPORT_INVALID = -1
+} BusTransport;
+
 typedef int (*bus_property_set_t) (sd_bus *bus, const char *member, sd_bus_message *m, sd_bus_error *error, void *userdata);
 
 struct bus_properties_map {
@@ -129,6 +135,21 @@ typedef struct UnitInfo {
 
 int bus_parse_unit_info(sd_bus_message *message, UnitInfo *u);
 
+DEFINE_TRIVIAL_CLEANUP_FUNC(sd_bus*, sd_bus_unref);
+DEFINE_TRIVIAL_CLEANUP_FUNC(sd_bus*, sd_bus_flush_close_unref);
+DEFINE_TRIVIAL_CLEANUP_FUNC(sd_bus_slot*, sd_bus_slot_unref);
+DEFINE_TRIVIAL_CLEANUP_FUNC(sd_bus_message*, sd_bus_message_unref);
+DEFINE_TRIVIAL_CLEANUP_FUNC(sd_bus_creds*, sd_bus_creds_unref);
+DEFINE_TRIVIAL_CLEANUP_FUNC(sd_bus_track*, sd_bus_track_unref);
+
+#define _cleanup_bus_unref_ _cleanup_(sd_bus_unrefp)
+#define _cleanup_bus_flush_close_unref_ _cleanup_(sd_bus_flush_close_unrefp)
+#define _cleanup_bus_slot_unref_ _cleanup_(sd_bus_slot_unrefp)
+#define _cleanup_bus_message_unref_ _cleanup_(sd_bus_message_unrefp)
+#define _cleanup_bus_creds_unref_ _cleanup_(sd_bus_creds_unrefp)
+#define _cleanup_bus_track_unref_ _cleanup_(sd_bus_slot_unrefp)
+#define _cleanup_bus_error_free_ _cleanup_(sd_bus_error_free)
+
 #define BUS_DEFINE_PROPERTY_GET_ENUM(function, name, type)              \
         int function(sd_bus *bus,                                       \
                      const char *path,                                  \
@@ -176,3 +197,6 @@ int bus_deserialize_and_dump_unit_file_changes(sd_bus_message *m, bool quiet, Un
 
 int bus_path_encode_unique(sd_bus *b, const char *prefix, const char *sender_id, const char *external_id, char **ret_path);
 int bus_path_decode_unique(const char *path, const char *prefix, char **ret_sender, char **ret_external);
+
+bool is_kdbus_wanted(void);
+bool is_kdbus_available(void);