sd-bus API，sd_bus_request_name返回权限被拒绝

Question

systemd 221中的总线API。当我在system bus中请求一个对象的名称时，它会打印出一个错误，说"Permission denied“。我以root用户身份运行输出文件。行"sd_bus_request_name(bus，"net.poettering.Calculator"，0)“抛出错误：”无法获取服务名称..：权限被拒绝“

我认为root应该拥有获取对象名称的权限。有人知道如何解决这个问题吗？

提前谢谢你。

以下是来自http://0pointer.net/blog/the-new-sd-bus-api-of-systemd.html的示例代码：

int main(int argc, char *argv[]) {
sd_bus_slot *slot = NULL;
sd_bus *bus = NULL;
int r;

r = sd_bus_default_system(&bus);
if (r < 0) {
    fprintf(stderr, "Failed to connect to system bus: %s\n", strerror(-r));
    goto finish;
}

/* Install the object */
r = sd_bus_add_object_vtable(bus,
                             &slot,
                             "/net/poettering/Calculator",
                             "net.poettering.Calculator",   /* interface name                             */calculator_vtable,
                             NULL);
if (r < 0) {
    fprintf(stderr, "Failed to issue method call: %s\n", strerror(-r));
    goto finish;
}

/* Take a well-known service name so that clients can find us */
r = sd_bus_request_name(bus, "net.poettering.Calculator", 0);
if (r < 0) {
    fprintf(stderr, "Failed to acquire service name: %s\n", strerror(-r));
    goto finish;
} 

Answer 1

典型的默认D-Bus配置不允许注册服务，除非明确允许。您需要允许root用户注册您的服务。创建/etc/dbus-1/system.d/net.poettering.Calculator.conf：

<!DOCTYPE busconfig PUBLIC
 "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
 "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
<busconfig>
  <policy user="root">
    <allow own="net.poettering.Calculator"/>
  </policy>
</busconfig>

有关详细信息，请阅读man dbus-daemon。

Answer 2

int main(int argc, char *argv[])
{
    sd_bus_slot *slot = NULL;
    sd_bus *bus = NULL;
    int r;
    r = sd_bus_default_system(&bus);
    if (r < 0) 
    {
        fprintf(stderr, "Failed to connect to system bus: %s\n", strerror(-r));
        goto finish;
    }
}