List WPA supplicant network properties using dbus-cpp - c++

Question

When trying to list network properties - https://w1.fi/wpa_supplicant/devel/dbus.html#dbus_network using dbus-cpp I get a number of errors about missing operator== for core::dbus::types::Variant
/usr/include/core/dbus/impl/object.h:185:17: required from ‘std::shared_ptr<core::dbus::Property<PropertyDescription> > core::dbus::Object::get_property() [with PropertyDescription = fi::w1::wpa_supplicant1::Network::Properties::Propertiez]’ /home/martin/ClionProjects/ang-wifi-controller/src/wpasupplicantclient.cpp:149:118: required from here /usr/include/c++/6/bits/stl_pair.h:364:51: error: no match for ‘operator==’ (operand types are ‘const core::dbus::types::Variant’ and ‘const core::dbus::types::Variant’)
{ return __x.first == __y.first && __x.second == __y.second; }
My code is based on dbus-cpp examples and http://quaintous.com/2015/08/30/cpp11-dbus/, but they only offer limited assistance.
The code representing Properties property is as follows:
namespace fi {
namespace w1 {
struct wpa_supplicant1 {
struct Network {
struct Properties {
struct Propertiez {
inline static std::string name() { return "Properties"; };
typedef Network Interface;
typedef std::map<std::string, core::dbus::types::Variant> ValueType;
static const bool readable = true;
static const bool writable = true;
};
};
};
And the offending line in .cpp is networkProxy->get_property<fi::w1::wpa_supplicant1::Network::Properties::Propertiez>();
I found that this question has already been asked at https://answers.launchpad.net/ubuntu/+source/dbus-cpp/+question/593271, but nobody offered any advice. Going through the code of packages listed by apt-cache rdepends libdbus-cpp5 also yielded no results.
I tried messing with the ValueType but it all resulted in runtime errors as the expected result probably truly is the map. It honestly seems like a bug in the library to me, but since this must be an obvious use case I am trying to find the mistake in my usage of the library. So what am I doing wrong?
Edit: Since I did not get any response, I am including minimal sample.
#include <core/dbus/bus.h>
#include <core/dbus/object.h>
#include <core/dbus/property.h>
#include <core/dbus/service.h>
#include <core/dbus/result.h>
#include <core/dbus/asio/executor.h>
#include <core/dbus/interfaces/properties.h>
#include <core/dbus/types/stl/string.h>
#include <core/dbus/types/stl/tuple.h>
#include <core/dbus/types/stl/vector.h>
#include <core/dbus/types/struct.h>
#include <core/dbus/types/variant.h>
using namespace std::chrono_literals;
using DBusDict = std::map<std::string, core::dbus::types::Variant>;
namespace fi {
namespace w1 {
struct wpa_supplicant1
{
struct GetInterface {
typedef wpa_supplicant1 Interface;
static const std::string &name()
{
static const std::string s("GetInterface");
return s;
}
inline static const std::chrono::milliseconds default_timeout() { return 1s; }
};
struct Iface
{
struct AddNetwork {
typedef Iface Interface;
static const std::string &name()
{
static const std::string s("AddNetwork");
return s;
}
inline static const std::chrono::milliseconds default_timeout() { return 1s; }
};
struct Properties
{
struct Networks
{
inline static std::string name()
{ return "Networks"; };
typedef Iface Interface;
typedef std::vector<core::dbus::types::ObjectPath> ValueType;
static const bool readable = true;
static const bool writable = false;
};
};
};
struct Network
{
struct Properties
{
struct Propertiez
{
inline static std::string name()
{ return "Properties"; };
typedef Network Interface;
typedef DBusDict ValueType;
static const bool readable = true;
static const bool writable = true;
};
};
};
};
};
};
namespace core {
namespace dbus {
namespace traits {
template <> struct Service<fi::w1::wpa_supplicant1> {
inline static const std::string &interface_name()
{
static const std::string s("fi.w1.wpa_supplicant1");
return s;
}
};
template <> struct Service<fi::w1::wpa_supplicant1::Iface> {
inline static const std::string &interface_name()
{
static const std::string s("fi.w1.wpa_supplicant1.Interface");
return s;
}
};
template <> struct Service<fi::w1::wpa_supplicant1::Network> {
inline static const std::string &interface_name()
{
static const std::string s("fi.w1.wpa_supplicant1.Network");
return s;
}
};
}
}
}
int main()
{
//bus
auto systemBus = std::make_shared<core::dbus::Bus>(core::dbus::WellKnownBus::system);
systemBus->install_executor(core::dbus::asio::make_executor(systemBus));
auto busThread = std::thread(std::bind(&core::dbus::Bus::run, systemBus));
//service
auto wpaService = core::dbus::Service::use_service<fi::w1::wpa_supplicant1>(systemBus);
auto wpaObjectPath = core::dbus::types::ObjectPath("/fi/w1/wpa_supplicant1");
auto wpaRootProxy = wpaService->object_for_path(wpaObjectPath);
//iface
auto ifacePath = wpaRootProxy->transact_method<fi::w1::wpa_supplicant1::GetInterface,
core::dbus::types::ObjectPath,
std::string>("wlan0"); //change this to your own wireless interface
auto wpaIfaceProxy = wpaService->object_for_path(ifacePath.value());
auto networkPaths = wpaIfaceProxy->get_property<fi::w1::wpa_supplicant1::Iface::Properties::Networks>();
//network
std::string ssid("network");
std::string password("password");
DBusDict args = {
{"ssid", core::dbus::types::Variant::encode(ssid)},
{"psk", core::dbus::types::Variant::encode(password)},
};
auto networkPath = wpaIfaceProxy->transact_method<fi::w1::wpa_supplicant1::Iface::AddNetwork,
core::dbus::types::ObjectPath,
DBusDict>(args);
auto networkProxy = wpaService->object_for_path(networkPath.value());
//get properties - uncomment line below to get compiler errors
//auto netProps = networkProxy->get_property<fi::w1::wpa_supplicant1::Network::Properties::Propertiez>();
while (true) {
continue;
}
}
Compile using: g++ $(pkg-config --cflags dbus-1 dbus-cpp) ./main.cpp $(pkg-config --libs dbus-1 dbus-cpp) -lpthread

Answer 1

Update:
dbus-cpp has an implementation for org.freedesktop.DBus.Properties.Get method.
Get:
auto resultVariant = dbus_object->invoke_method_synchronously
/*Method*/ <dbus::interfaces::Properties::Get,
/*Output Type*/ dbus::types::Variant,
/*Input Types*/ std::string, std::string>
("fi.w1.wpa_supplicant1.Network","Properties").value();
auto props = resultVariant.as<std::map<std::string, dbus::types::Variant>>();
Sadly, the Set method, while also implemented, does NOT seem to work with any ArgumentTypes with nested Variants within them. So:
a{sv} : std::map<std::string, core::dbus::types::Variant>
a{v} : std::vector<core::dbus::types::Variant>
in a Set method call will actually cause the program to crash. (Didn't test more)
Old post:
I ran into the same bug today and found a workaround for at least getting the properties value.
Instead of using
auto prop = dbus_object->get_property<fi::w1::wpa_supplicant1::Network::Properties::Propertiez>();
try
//returns std::map<std::string, core::dbus::types::Variant>>
auto props = dbus_object->get_all_properties<fi::w1::wpa_supplicant1::Network>();
auto prop = props["Properties"];
auto prop_value = prop.as<std::map<std::string, core::dbus::types::Variant>>();
As far as I understand the bug, dbus-cpp makes use of the
org.freedesktop.DBus.Properties interface to read out Properties.
So dbus_object->get_property() tries to invoke a org.freedesktop.DBus.Properties.Get and fails to compile because of the missing ==operator implementation. (Something it needs for casting the specific ValueType, I guess)
dbus_object->get_all_properties() invokes org.freedesktop.DBus.Properties.GetAll which does not need a specific ValueType, so it works.
Of course this is just a workaround to getting properties, since setting a property value is bound to the same shared_pointer as getting it.

Answer 2

As the documentation for fi.w1.wpa_supplicant1.Network.Properties.Properties says:
[...] All values are string type, e.g., frequency is "2437", not 2437.
So try to define DBusDict as follow:
using DBusDict = std::map<std::string, std::string>;