Dispute distribution implementation (#3282)

* Dispute protocol.

* Dispute distribution protocol.

* Get network requests routed.

* WIP: Basic dispute sender logic.

* Basic validator determination logic.

* WIP: Getting things to typecheck.

* Slightly larger timeout.

* More typechecking stuff.

* Cleanup.

* Finished most of the sending logic.

* Handle active leaves updates

- Cleanup dead disputes
- Update sends for new sessions
- Retry on errors

* Pass sessions in already.

* Startup dispute sending.

* Provide incoming decoding facilities

and use them in statement-distribution.

* Relaxed runtime util requirements.

We only need a `SubsystemSender` not a full `SubsystemContext`.

* Better usability of incoming requests.

Make it possible to consume stuff without clones.

* Add basic receiver functionality.

* Cleanup + fixes for sender.

* One more sender fix.

* Start receiver.

* Make sure to send responses back.

* WIP: Exposed authority discovery

* Make tests pass.

* Fully featured receiver.

* Decrease cost of `NotAValidator`.

* Make `RuntimeInfo` LRU cache size configurable.

* Cache more sessions.

* Fix collator protocol.

* Disable metrics for now.

* Make dispute-distribution a proper subsystem.

* Fix naming.

* Code style fixes.

* Factored out 4x copied mock function.

* WIP: Tests.

* Whitespace cleanup.

* Accessor functions.

* More testing.

* More Debug instances.

* Fix busy loop.

* Working tests.

* More tests.

* Cleanup.

* Fix build.

* Basic receiving test.

* Non validator message gets dropped.

* More receiving tests.

* Test nested and subsequent imports.

* Fix spaces.

* Better formatted imports.

* Import cleanup.

* Metrics.

* Message -> MuxedMessage

* Message -> MuxedMessage

* More review remarks.

* Add missing metrics.rs.

* Fix flaky test.

* Dispute coordinator - deliver confirmations.

* Send out `DisputeMessage` on issue local statement.

* Unwire dispute distribution.

* Review remarks.

* Review remarks.

* Better docs.

polkadot/node/network/statement-distribution/src/responder.rs

@@ -16,8 +16,6 @@
 
 use futures::{SinkExt, StreamExt, channel::{mpsc, oneshot}, stream::FuturesUnordered};
 
-use parity_scale_codec::Decode;
-
 use polkadot_node_network_protocol::{
 	PeerId, UnifiedReputationChange as Rep,
 	request_response::{
@@ -85,35 +83,26 @@ pub async fn respond(
 			Some(v) => v,
 		};
 
-		let sc_network::config::IncomingRequest {
-			payload,
-			peer,
-			pending_response,
-		} = raw;
-
-		let payload = match StatementFetchingRequest::decode(&mut payload.as_ref()) {
+		let req =
+			match IncomingRequest::<StatementFetchingRequest>::try_from_raw(
+				raw,
+				vec![COST_INVALID_REQUEST],
+			) {
 			Err(err) => {
 				tracing::debug!(
 					target: LOG_TARGET,
 					?err,
 					"Decoding request failed"
 				);
-				report_peer(pending_response, COST_INVALID_REQUEST);
 				continue
 			}
 			Ok(payload) => payload,
 		};
 
-		let req = IncomingRequest::new(
-			peer,
-			payload,
-			pending_response
-		);
-
 		let (tx, rx) = oneshot::channel();
 		if let Err(err) = sender.feed(
 			ResponderMessage::GetData {
-				requesting_peer: peer,
+				requesting_peer: req.peer,
 				relay_parent: req.payload.relay_parent,
 				candidate_hash: req.payload.candidate_hash,
 				tx,
@@ -152,20 +141,3 @@ pub async fn respond(
 		}
 	}
 }
-
-/// Report peer who sent us a request.
-fn report_peer(
-	tx: oneshot::Sender<sc_network::config::OutgoingResponse>,
-	rep: Rep,
-) {
-	if let Err(_) = tx.send(sc_network::config::OutgoingResponse {
-		result: Err(()),
-		reputation_changes: vec![rep.into_base_rep()],
-		sent_feedback: None,
-	}) {
-		tracing::debug!(
-			target: LOG_TARGET,
-			"Reporting peer failed."
-		);
-	}
-}