Add a DirectedGossip struct (#6803)

* Add a DirectedGossip struct

* Move protocol from prototype::new to biuld

* More traits impls

* Explain ordering

* Apply suggestions from code review

Co-authored-by: Toralf Wittner <tw@dtex.org>

* Address concerns

* Add basic test

* Concerns

* More concerns

* Remove QueueSenderPrototype

* Rename

* Apply suggestions from code review

Co-authored-by: Max Inden <mail@max-inden.de>

Co-authored-by: Toralf Wittner <tw@dtex.org>
Co-authored-by: parity-processbot <>
Co-authored-by: Max Inden <mail@max-inden.de>

substrate/client/network/src/lib.rs

@@ -15,6 +15,7 @@
 
 // You should have received a copy of the GNU General Public License
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
+
 #![warn(unused_extern_crates)]
 #![warn(missing_docs)]
 
@@ -259,6 +260,7 @@ mod utils;
 
 pub mod config;
 pub mod error;
+pub mod gossip;
 pub mod network_state;
 
 pub use service::{NetworkService, NetworkWorker};