From ef01fb10f7a4159a2d2800d2c7c60b247e575ba7 Mon Sep 17 00:00:00 2001
From: David Herrmann <dh.herrmann@gmail.com>
Date: Wed, 6 May 2015 18:18:43 +0200
Subject: [PATCH] bus: don't switch to kdbus if not requested

Whenever systemd is re-executed, it tries to create a system bus via
kdbus. If the system did not have kdbus loaded during bootup, but the
module is loaded later on manually, this will cause two system buses
running (kdbus and dbus-daemon in parallel).

This patch makes sure we never try to create kdbus buses if it wasn't
explicitly requested on the command-line.
---
 src/libelogind/sd-bus/bus-util.c | 27 +++++++++++++++++++++++++++
 src/libelogind/sd-bus/bus-util.h |  3 +++
 2 files changed, 30 insertions(+)

diff --git a/src/libelogind/sd-bus/bus-util.c b/src/libelogind/sd-bus/bus-util.c
index 32a17c6ea..a826fe2b8 100644
--- a/src/libelogind/sd-bus/bus-util.c
+++ b/src/libelogind/sd-bus/bus-util.c
@@ -2041,3 +2041,30 @@ 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;
+        int r;
+
+        if (get_proc_cmdline_key("kdbus", NULL) <= 0) {
+                r = get_proc_cmdline_key("kdbus=", &value);
+                if (r <= 0 || parse_boolean(value) != 1)
+                        return false;
+        }
+
+        return true;
+}
+
+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/libelogind/sd-bus/bus-util.h b/src/libelogind/sd-bus/bus-util.h
index 6216a2c8b..0594cda5f 100644
--- a/src/libelogind/sd-bus/bus-util.h
+++ b/src/libelogind/sd-bus/bus-util.h
@@ -204,3 +204,6 @@ int bus_deserialize_and_dump_unit_file_changes(sd_bus_message *m, bool quiet);
 
 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);
-- 
2.30.2