Gossip refactoring (#1811)

* First part of gossip protocol refactoring

* Message validation in GRANDPA

* Reverted to time-based expiration for future round messages

* Removed collect_garbage_for_topic

* Use consensus engine id instead of kind

* Use try_init

Co-Authored-By: arkpar <arkady.paronyan@gmail.com>

* Comment

Co-Authored-By: arkpar <arkady.paronyan@gmail.com>

* Added expiration check on broadcast

Co-Authored-By: arkpar <arkady.paronyan@gmail.com>

* Apply suggestions from code review

Co-Authored-By: arkpar <arkady.paronyan@gmail.com>

* Style

* Style

substrate/core/network/src/message.rs

@@ -30,6 +30,9 @@ pub use self::generic::{
 /// A unique ID of a request.
 pub type RequestId = u64;
 
+/// Consensus engine unique ID.
+pub type ConsensusEngineId = [u8; 4];
+
 /// Type alias for using the message type using block type parameters.
 pub type Message<B> = generic::Message<
 	<B as BlockT>::Header,
@@ -132,10 +135,16 @@ pub mod generic {
 	use crate::config::Roles;
 	use super::{
 		BlockAttributes, RemoteCallResponse, RemoteReadResponse,
-		RequestId, Transactions, Direction
+		RequestId, Transactions, Direction, ConsensusEngineId,
 	};
-	/// Consensus is opaque to us
-	pub type ConsensusMessage = Vec<u8>;
+	/// Consensus is mostly opaque to us
+	#[derive(Debug, PartialEq, Eq, Clone, Encode, Decode)]
+	pub struct ConsensusMessage {
+		/// Identifies consensus engine.
+		pub engine_id: ConsensusEngineId,
+		/// Message payload.
+		pub data: Vec<u8>,
+	}
 
 	/// Block data sent in the response.
 	#[derive(Debug, PartialEq, Eq, Clone, Encode, Decode)]
@@ -177,7 +186,7 @@ pub mod generic {
 		/// Transactions.
 		Transactions(Transactions<Extrinsic>),
 		/// Consensus protocol message.
-		Consensus(Hash, ConsensusMessage, bool), // topic, opaque Vec<u8>, broadcast
+		Consensus(ConsensusMessage),
 		/// Remote method call request.
 		RemoteCallRequest(RemoteCallRequest<Hash>),
 		/// Remote method call response.
@@ -216,6 +225,8 @@ pub mod generic {
 	pub struct Status<Hash, Number> {
 		/// Protocol version.
 		pub version: u32,
+		/// Minimum supported version.
+		pub min_supported_version: u32,
 		/// Supported roles.
 		pub roles: Roles,
 		/// Best block number.