feat: add support for direct connections (#350)

* feat: add support for direct connections

* refactor: simplify a bit, change comments, extend tests

* fix: compiler warning about unused variable

* docs: add section on direct connections to the tutorial

---------

Co-authored-by: Maksim Fedyarov <m.fedyarov@omp.ru>
Co-authored-by: Stanislav Angelovič <stanislav.angelovic@protonmail.com>

src/Connection.cpp

@@ -70,6 +70,21 @@ Connection::Connection(std::unique_ptr<ISdBus>&& interface, remote_system_bus_t,
 {
 }
 
+Connection::Connection(std::unique_ptr<ISdBus>&& interface, private_bus_t, const std::string& address)
+    : Connection(std::move(interface), [&](sd_bus** bus) { return iface_->sd_bus_open_direct(bus, address.c_str()); })
+{
+}
+
+Connection::Connection(std::unique_ptr<ISdBus>&& interface, private_bus_t, int fd)
+        : Connection(std::move(interface), [&](sd_bus** bus) { return iface_->sd_bus_open_direct(bus, fd); })
+{
+}
+
+Connection::Connection(std::unique_ptr<ISdBus>&& interface, server_bus_t, int fd)
+    : Connection(std::move(interface), [&](sd_bus** bus) { return iface_->sd_bus_open_server(bus, fd); })
+{
+}
+
 Connection::Connection(std::unique_ptr<ISdBus>&& interface, pseudo_bus_t)
     : iface_(std::move(interface))
     , bus_(openPseudoBus())
@@ -262,7 +277,7 @@ MethodCall Connection::createMethodCall( const std::string& destination
 
     auto r = iface_->sd_bus_message_new_method_call( bus_.get()
                                                    , &sdbusMsg
-                                                   , destination.c_str()
+                                                   , destination.empty() ? nullptr : destination.c_str()
                                                    , objectPath.c_str()
                                                    , interfaceName.c_str()
                                                    , methodName.c_str() );
@@ -527,7 +542,8 @@ std::string Connection::composeSignalMatchFilter( const std::string &sender
     std::string filter;
 
     filter += "type='signal',";
-    filter += "sender='" + sender + "',";
+    if (!sender.empty())
+        filter += "sender='" + sender + "',";
     filter += "interface='" + interfaceName + "',";
     filter += "member='" + signalName + "',";
     filter += "path='" + objectPath + "'";
@@ -661,7 +677,6 @@ std::unique_ptr<sdbus::IConnection> createSessionBusConnection(const std::string
 std::unique_ptr<sdbus::IConnection> createSessionBusConnectionWithAddress(const std::string &address)
 {
     auto interface = std::make_unique<sdbus::internal::SdBus>();
-    assert(interface != nullptr);
     return std::make_unique<sdbus::internal::Connection>(std::move(interface), Connection::custom_session_bus, address);
 }
 
@@ -671,4 +686,22 @@ std::unique_ptr<sdbus::IConnection> createRemoteSystemBusConnection(const std::s
     return std::make_unique<sdbus::internal::Connection>(std::move(interface), Connection::remote_system_bus, host);
 }
 
+std::unique_ptr<sdbus::IConnection> createDirectBusConnection(const std::string& address)
+{
+    auto interface = std::make_unique<sdbus::internal::SdBus>();
+    return std::make_unique<sdbus::internal::Connection>(std::move(interface), Connection::private_bus, address);
+}
+
+std::unique_ptr<sdbus::IConnection> createDirectBusConnection(int fd)
+{
+    auto interface = std::make_unique<sdbus::internal::SdBus>();
+    return std::make_unique<sdbus::internal::Connection>(std::move(interface), Connection::private_bus, fd);
+}
+
+std::unique_ptr<sdbus::IConnection> createServerBus(int fd)
+{
+    auto interface = std::make_unique<sdbus::internal::SdBus>();
+    return std::make_unique<sdbus::internal::Connection>(std::move(interface), Connection::server_bus, fd);
+}
+
 } // namespace sdbus

src/Connection.h

@@ -57,6 +57,10 @@ namespace sdbus::internal {
         inline static constexpr custom_session_bus_t custom_session_bus{};
         struct remote_system_bus_t{};
         inline static constexpr remote_system_bus_t remote_system_bus{};
+        struct private_bus_t{};
+        inline static constexpr private_bus_t private_bus{};
+        struct server_bus_t{};
+        inline static constexpr server_bus_t server_bus{};
         struct pseudo_bus_t{}; // A bus connection that is not really established with D-Bus daemon
         inline static constexpr pseudo_bus_t pseudo_bus{};
 
@@ -65,6 +69,9 @@ namespace sdbus::internal {
         Connection(std::unique_ptr<ISdBus>&& interface, session_bus_t);
         Connection(std::unique_ptr<ISdBus>&& interface, custom_session_bus_t, const std::string& address);
         Connection(std::unique_ptr<ISdBus>&& interface, remote_system_bus_t, const std::string& host);
+        Connection(std::unique_ptr<ISdBus>&& interface, private_bus_t, const std::string& address);
+        Connection(std::unique_ptr<ISdBus>&& interface, private_bus_t, int fd);
+        Connection(std::unique_ptr<ISdBus>&& interface, server_bus_t, int fd);
         Connection(std::unique_ptr<ISdBus>&& interface, pseudo_bus_t);
         ~Connection() override;
 

src/ISdBus.h

@@ -71,6 +71,9 @@ namespace sdbus::internal {
         virtual int sd_bus_open_user(sd_bus **ret) = 0;
         virtual int sd_bus_open_user_with_address(sd_bus **ret, const char* address) = 0;
         virtual int sd_bus_open_system_remote(sd_bus **ret, const char* host) = 0;
+        virtual int sd_bus_open_direct(sd_bus **ret, const char* address) = 0;
+        virtual int sd_bus_open_direct(sd_bus **ret, int fd) = 0;
+        virtual int sd_bus_open_server(sd_bus **ret, int fd) = 0;
         virtual int sd_bus_request_name(sd_bus *bus, const char *name, uint64_t flags) = 0;
         virtual int sd_bus_release_name(sd_bus *bus, const char *name) = 0;
         virtual int sd_bus_get_unique_name(sd_bus *bus, const char **name) = 0;

src/SdBus.cpp

@@ -194,26 +194,98 @@ int SdBus::sd_bus_open_user_with_address(sd_bus **ret, const char* address)
 {
     sd_bus* bus = nullptr;
 
-    int r = sd_bus_new(&bus);
+    int r = ::sd_bus_new(&bus);
     if (r < 0)
         return r;
 
-    r = sd_bus_set_address(bus, address);
+    r = ::sd_bus_set_address(bus, address);
     if (r < 0)
         return r;
 
-    r = sd_bus_set_bus_client(bus, true);
+    r = ::sd_bus_set_bus_client(bus, true);
     if (r < 0)
         return r;
 
     // Copying behavior from
     // https://github.com/systemd/systemd/blob/fee6441601c979165ebcbb35472036439f8dad5f/src/libsystemd/sd-bus/sd-bus.c#L1381
     // Here, we make the bus as trusted
-    r = sd_bus_set_trusted(bus, true);
+    r = ::sd_bus_set_trusted(bus, true);
     if (r < 0)
         return r;
 
-    r = sd_bus_start(bus);
+    r = ::sd_bus_start(bus);
+    if (r < 0)
+        return r;
+
+    *ret = bus;
+
+    return 0;
+}
+
+int SdBus::sd_bus_open_direct(sd_bus **ret, const char* address)
+{
+    sd_bus* bus = nullptr;
+
+    int r = ::sd_bus_new(&bus);
+    if (r < 0)
+        return r;
+
+    r = ::sd_bus_set_address(bus, address);
+    if (r < 0)
+        return r;
+
+    r = ::sd_bus_start(bus);
+    if (r < 0)
+        return r;
+
+    *ret = bus;
+
+    return 0;
+}
+
+int SdBus::sd_bus_open_direct(sd_bus **ret, int fd)
+{
+    sd_bus* bus = nullptr;
+
+    int r = ::sd_bus_new(&bus);
+    if (r < 0)
+        return r;
+
+    r = ::sd_bus_set_fd(bus, fd, fd);
+    if (r < 0)
+        return r;
+
+    r = ::sd_bus_start(bus);
+    if (r < 0)
+        return r;
+
+    *ret = bus;
+
+    return 0;
+}
+
+int SdBus::sd_bus_open_server(sd_bus **ret, int fd)
+{
+    sd_bus* bus = nullptr;
+
+    int r = ::sd_bus_new(&bus);
+    if (r < 0)
+        return r;
+
+    r = ::sd_bus_set_fd(bus, fd, fd);
+    if (r < 0)
+        return r;
+
+    sd_id128_t id;
+    r = ::sd_id128_randomize(&id);
+    if (r < 0)
+        return r;
+
+    r = ::sd_bus_set_server(bus, true, id);
+    if (r < 0)
+        return r;
+
+    r = ::sd_bus_start(bus);
     if (r < 0)
         return r;
 
@@ -270,7 +342,7 @@ int SdBus::sd_bus_add_match(sd_bus *bus, sd_bus_slot **slot, const char *match,
 {
     std::lock_guard lock(sdbusMutex_);
 
-    return :: sd_bus_add_match(bus, slot, match, callback, userdata);
+    return ::sd_bus_add_match(bus, slot, match, callback, userdata);
 }
 
 sd_bus_slot* SdBus::sd_bus_slot_unref(sd_bus_slot *slot)

src/SdBus.h

@@ -63,6 +63,9 @@ public:
     virtual int sd_bus_open_user(sd_bus **ret) override;
     virtual int sd_bus_open_user_with_address(sd_bus **ret, const char* address) override;
     virtual int sd_bus_open_system_remote(sd_bus **ret, const char* hsot) override;
+    virtual int sd_bus_open_direct(sd_bus **ret, const char* address) override;
+    virtual int sd_bus_open_direct(sd_bus **ret, int fd) override;
+    virtual int sd_bus_open_server(sd_bus **ret, int fd) override;
     virtual int sd_bus_request_name(sd_bus *bus, const char *name, uint64_t flags) override;
     virtual int sd_bus_release_name(sd_bus *bus, const char *name) override;
     virtual int sd_bus_get_unique_name(sd_bus *bus, const char **name) override;

src/Utils.h

@@ -31,17 +31,17 @@
 #include SDBUS_HEADER
 
 #if LIBSYSTEMD_VERSION>=246
-#define SDBUS_CHECK_OBJECT_PATH(_PATH)                                                                                              \
-    SDBUS_THROW_ERROR_IF(!sd_bus_object_path_is_valid(_PATH.c_str()), "Invalid object path '" + _PATH + "' provided", EINVAL)       \
+#define SDBUS_CHECK_OBJECT_PATH(_PATH)                                                                                                            \
+    SDBUS_THROW_ERROR_IF(!sd_bus_object_path_is_valid(_PATH.c_str()), "Invalid object path '" + _PATH + "' provided", EINVAL)                     \
     /**/
-#define SDBUS_CHECK_INTERFACE_NAME(_NAME)                                                                                           \
-    SDBUS_THROW_ERROR_IF(!sd_bus_interface_name_is_valid(_NAME.c_str()), "Invalid interface name '" + _NAME + "' provided", EINVAL) \
+#define SDBUS_CHECK_INTERFACE_NAME(_NAME)                                                                                                         \
+    SDBUS_THROW_ERROR_IF(!sd_bus_interface_name_is_valid(_NAME.c_str()), "Invalid interface name '" + _NAME + "' provided", EINVAL)               \
     /**/
-#define SDBUS_CHECK_SERVICE_NAME(_NAME)                                                                                             \
-    SDBUS_THROW_ERROR_IF(!sd_bus_service_name_is_valid(_NAME.c_str()), "Invalid service name '" + _NAME + "' provided", EINVAL)     \
+#define SDBUS_CHECK_SERVICE_NAME(_NAME)                                                                                                           \
+    SDBUS_THROW_ERROR_IF(!_NAME.empty() && !sd_bus_service_name_is_valid(_NAME.c_str()), "Invalid service name '" + _NAME + "' provided", EINVAL) \
     /**/
-#define SDBUS_CHECK_MEMBER_NAME(_NAME)                                                                                              \
-    SDBUS_THROW_ERROR_IF(!sd_bus_member_name_is_valid(_NAME.c_str()), "Invalid member name '" + _NAME + "' provided", EINVAL)       \
+#define SDBUS_CHECK_MEMBER_NAME(_NAME)                                                                                                            \
+    SDBUS_THROW_ERROR_IF(!sd_bus_member_name_is_valid(_NAME.c_str()), "Invalid member name '" + _NAME + "' provided", EINVAL)                     \
     /**/
 #else
 #define SDBUS_CHECK_OBJECT_PATH(_PATH)