sd-bus API，sd_bus_request_name 返回权限被拒绝

Question

systemd 221 中的总线 API。当我为系统总线中的对象请求名称时，它会打印出一条错误消息，指出“权限被拒绝”。我以 root 身份运行输出文件。“sd_bus_request_name(bus, "net.poettering.Calculator", 0)” 行抛出错误：“无法获取服务名称..：权限被拒绝”

我认为 root 应该有权获取对象的名称。有谁知道如何解决这个问题？

先感谢您。

这是来自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 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>

阅读 man dbus-daemon 了解详细信息。

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;
    }
}