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/bridge/src/lib.rs

@@ -24,6 +24,7 @@ use parity_scale_codec::{Encode, Decode};
 use parking_lot::Mutex;
 use futures::prelude::*;
 use futures::stream::BoxStream;
+use polkadot_subsystem::messages::DisputeDistributionMessage;
 use sc_network::Event as NetworkEvent;
 use sp_consensus::SyncOracle;
 
@@ -57,7 +58,8 @@ use polkadot_node_subsystem_util::metrics::{self, prometheus};
 /// To be added to [`NetworkConfiguration::extra_sets`].
 pub use polkadot_node_network_protocol::peer_set::{peer_sets_info, IsAuthority};
 
-use std::collections::{HashMap, hash_map, HashSet};
+use std::collections::HashSet;
+use std::collections::{HashMap, hash_map};
 use std::sync::Arc;
 
 mod validator_discovery;
@@ -66,12 +68,14 @@ mod validator_discovery;
 ///
 /// Defines the `Network` trait with an implementation for an `Arc<NetworkService>`.
 mod network;
-use network::{Network, send_message, get_peer_id_by_authority_id};
+use network::{Network, send_message};
 
 /// Request multiplexer for combining the multiple request sources into a single `Stream` of `AllMessages`.
 mod multiplexer;
 pub use multiplexer::RequestMultiplexer;
 
+use crate::network::get_peer_id_by_authority_id;
+
 #[cfg(test)]
 mod tests;
 
@@ -304,7 +308,7 @@ impl<N, AD> NetworkBridge<N, AD> {
 impl<Net, AD, Context> Subsystem<Context, SubsystemError> for NetworkBridge<Net, AD>
 	where
 		Net: Network + Sync,
-		AD: validator_discovery::AuthorityDiscovery,
+		AD: validator_discovery::AuthorityDiscovery + Clone,
 		Context: SubsystemContext<Message = NetworkBridgeMessage> + overseer::SubsystemContext<Message = NetworkBridgeMessage>,
 {
 	fn start(mut self, ctx: Context) -> SpawnedSubsystem {
@@ -380,7 +384,7 @@ where
 	Context: SubsystemContext<Message = NetworkBridgeMessage>,
 	Context: overseer::SubsystemContext<Message = NetworkBridgeMessage>,
 	N: Network,
-	AD: validator_discovery::AuthorityDiscovery,
+	AD: validator_discovery::AuthorityDiscovery + Clone,
 {
 	// This is kept sorted, descending, by block number.
 	let mut live_heads: Vec<ActivatedLeaf> = Vec::with_capacity(MAX_VIEW_HEADS);
@@ -877,7 +881,7 @@ async fn run_network<N, AD, Context>(
 ) -> SubsystemResult<()>
 where
 	N: Network,
-	AD: validator_discovery::AuthorityDiscovery,
+	AD: validator_discovery::AuthorityDiscovery + Clone,
 	Context: SubsystemContext<Message=NetworkBridgeMessage> + overseer::SubsystemContext<Message=NetworkBridgeMessage>,
 {
 	let shared = Shared::default();
@@ -894,6 +898,10 @@ where
 		.get_statement_fetching()
 		.expect("Gets initialized, must be `Some` on startup. qed.");
 
+	let dispute_receiver = request_multiplexer
+		.get_dispute_sending()
+		.expect("Gets initialized, must be `Some` on startup. qed.");
+
 	let (remote, network_event_handler) = handle_network_messages::<>(
 		ctx.sender().clone(),
 		network_service.clone(),
@@ -906,6 +914,9 @@ where
 
 	ctx.spawn("network-bridge-network-worker", Box::pin(remote))?;
 
+	ctx.send_message(
+		DisputeDistributionMessage::DisputeSendingReceiver(dispute_receiver)
+	).await;
 	ctx.send_message(
 		StatementDistributionMessage::StatementFetchingReceiver(statement_receiver)
 	).await;