Implement Network Bridge (#1280)

* network bridge skeleton

* move some primitives around and add debug impls

* protocol registration glue & abstract network interface

* add send_msgs to subsystemctx

* select logic

* transform different events into actions and handle

* implement remaining network bridge state machine

* start test skeleton

* make network methods asynchronous

* extract subsystem out to subsystem crate

* port over overseer to subsystem context trait

* fix minimal example

* fix overseer doc test

* update network-bridge crate

* write a subsystem test-helpers crate

* write a network test helper for network-bridge

* set up (broken) view test

* Revamp network to be more async-friendly and not require Sync

* fix spacing

* fix test compilation

* insert side-channel for actions

* Add some more message types to AllMessages

* introduce a test harness

* add some tests

* ensure service compiles and passes tests

* fix typo

* fix service-new compilation

* Subsystem test helpers send messages synchronously

* remove smelly action inspector

* remove superfluous let binding

* fix warnings

* Update node/network/bridge/src/lib.rs

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

* fix compilation

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

polkadot/node/subsystem/src/messages.rs

@@ -0,0 +1,226 @@
+// Copyright 2017-2020 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Message types for the overseer and subsystems.
+//!
+//! These messages are intended to define the protocol by which different subsystems communicate with each
+//! other and signals that they receive from an overseer to coordinate their work.
+//! This is intended for use with the `polkadot-overseer` crate.
+//!
+//! Subsystems' APIs are defined separately from their implementation, leading to easier mocking.
+
+use futures::channel::{mpsc, oneshot};
+
+use sc_network::{ObservedRole, ReputationChange, PeerId};
+use polkadot_primitives::{BlockNumber, Hash, Signature};
+use polkadot_primitives::parachain::{
+	AbridgedCandidateReceipt, PoVBlock, ErasureChunk, BackedCandidate, Id as ParaId,
+	SignedAvailabilityBitfield, SigningContext, ValidatorId, ValidationCode, ValidatorIndex,
+};
+use polkadot_node_primitives::{
+	MisbehaviorReport, SignedFullStatement, View, ProtocolId,
+};
+
+/// A notification of a new backed candidate.
+#[derive(Debug)]
+pub struct NewBackedCandidate(pub BackedCandidate);
+
+/// Messages received by the Candidate Selection subsystem.
+#[derive(Debug)]
+pub enum CandidateSelectionMessage {
+	/// We recommended a particular candidate to be seconded, but it was invalid; penalize the collator.
+	/// The hash is the relay parent.
+	Invalid(Hash, AbridgedCandidateReceipt),
+}
+
+/// Messages received by the Candidate Backing subsystem.
+#[derive(Debug)]
+pub enum CandidateBackingMessage {
+	/// Registers a stream listener for updates to the set of backable candidates that could be backed
+	/// in a child of the given relay-parent, referenced by its hash.
+	RegisterBackingWatcher(Hash, mpsc::Sender<NewBackedCandidate>),
+	/// Note that the Candidate Backing subsystem should second the given candidate in the context of the
+	/// given relay-parent (ref. by hash). This candidate must be validated.
+	Second(Hash, AbridgedCandidateReceipt),
+	/// Note a validator's statement about a particular candidate. Disagreements about validity must be escalated
+	/// to a broader check by Misbehavior Arbitration. Agreements are simply tallied until a quorum is reached.
+	Statement(Hash, SignedFullStatement),
+}
+
+/// Blanket error for validation failing.
+#[derive(Debug)]
+pub struct ValidationFailed;
+
+/// Messages received by the Validation subsystem
+#[derive(Debug)]
+pub enum CandidateValidationMessage {
+	/// Validate a candidate, sending a side-channel response of valid or invalid.
+	///
+	/// Provide the relay-parent in whose context this should be validated, the full candidate receipt,
+	/// and the PoV.
+	Validate(
+		Hash,
+		AbridgedCandidateReceipt,
+		PoVBlock,
+		oneshot::Sender<Result<(), ValidationFailed>>,
+	),
+}
+
+/// Events from network.
+#[derive(Debug, Clone)]
+pub enum NetworkBridgeEvent {
+	/// A peer has connected.
+	PeerConnected(PeerId, ObservedRole),
+
+	/// A peer has disconnected.
+	PeerDisconnected(PeerId),
+
+	/// Peer has sent a message.
+	PeerMessage(PeerId, Vec<u8>),
+
+	/// Peer's `View` has changed.
+	PeerViewChange(PeerId, View),
+
+	/// Our `View` has changed.
+	OurViewChange(View),
+}
+
+/// Messages received by the network bridge subsystem.
+#[derive(Debug)]
+pub enum NetworkBridgeMessage {
+	/// Register an event producer on startup.
+	RegisterEventProducer(ProtocolId, fn(NetworkBridgeEvent) -> AllMessages),
+
+	/// Report a peer for their actions.
+	ReportPeer(PeerId, ReputationChange),
+
+	/// Send a message to multiple peers.
+	SendMessage(Vec<PeerId>, ProtocolId, Vec<u8>),
+}
+
+/// Availability Distribution Message.
+#[derive(Debug)]
+pub enum AvailabilityDistributionMessage {
+	/// Distribute an availability chunk to other validators.
+	DistributeChunk(Hash, ErasureChunk),
+
+	/// Fetch an erasure chunk from networking by candidate hash and chunk index.
+	FetchChunk(Hash, u32),
+
+	/// Event from the network bridge.
+	NetworkBridgeUpdate(NetworkBridgeEvent),
+}
+
+/// Bitfield distribution message.
+#[derive(Debug)]
+pub enum BitfieldDistributionMessage {
+	/// Distribute a bitfield via gossip to other validators.
+	DistributeBitfield(Hash, SignedAvailabilityBitfield),
+
+	/// Event from the network bridge.
+	NetworkBridgeUpdate(NetworkBridgeEvent),
+}
+
+/// Availability store subsystem message.
+#[derive(Debug)]
+pub enum AvailabilityStoreMessage {
+	/// Query a `PoVBlock` from the AV store.
+	QueryPoV(Hash, oneshot::Sender<Option<PoVBlock>>),
+
+	/// Query an `ErasureChunk` from the AV store.
+	QueryChunk(Hash, ValidatorIndex, oneshot::Sender<ErasureChunk>),
+
+	/// Store an `ErasureChunk` in the AV store.
+	StoreChunk(Hash, ValidatorIndex, ErasureChunk),
+}
+
+/// A request to the Runtime API subsystem.
+#[derive(Debug)]
+pub enum RuntimeApiRequest {
+	/// Get the current validator set.
+	Validators(oneshot::Sender<Vec<ValidatorId>>),
+	/// Get a signing context for bitfields and statements.
+	SigningContext(oneshot::Sender<SigningContext>),
+	/// Get the validation code for a specific para, assuming execution under given block number, and
+	/// an optional block number representing an intermediate parablock executed in the context of
+	/// that block.
+	ValidationCode(ParaId, BlockNumber, Option<BlockNumber>, oneshot::Sender<ValidationCode>),
+}
+
+/// A message to the Runtime API subsystem.
+#[derive(Debug)]
+pub enum RuntimeApiMessage {
+	/// Make a request of the runtime API against the post-state of the given relay-parent.
+	Request(Hash, RuntimeApiRequest),
+}
+
+/// Statement distribution message.
+#[derive(Debug)]
+pub enum StatementDistributionMessage {
+	/// We have originated a signed statement in the context of
+	/// given relay-parent hash and it should be distributed to other validators.
+	Share(Hash, SignedFullStatement),
+	/// Event from the network bridge.
+	NetworkBridgeUpdate(NetworkBridgeEvent),
+}
+
+/// This data becomes intrinsics or extrinsics which should be included in a future relay chain block.
+#[derive(Debug)]
+pub enum ProvisionableData {
+	/// This bitfield indicates the availability of various candidate blocks.
+	Bitfield(Hash, SignedAvailabilityBitfield),
+	/// The Candidate Backing subsystem believes that this candidate is valid, pending availability.
+	BackedCandidate(BackedCandidate),
+	/// Misbehavior reports are self-contained proofs of validator misbehavior.
+	MisbehaviorReport(Hash, MisbehaviorReport),
+	/// Disputes trigger a broad dispute resolution process.
+	Dispute(Hash, Signature),
+}
+
+/// Message to the Provisioner.
+///
+/// In all cases, the Hash is that of the relay parent.
+#[derive(Debug)]
+pub enum ProvisionerMessage {
+	/// This message allows potential block authors to be kept updated with all new authorship data
+	/// as it becomes available.
+	RequestBlockAuthorshipData(Hash, mpsc::Sender<ProvisionableData>),
+	/// This data should become part of a relay chain block
+	ProvisionableData(ProvisionableData),
+}
+
+/// A message type tying together all message types that are used across Subsystems.
+#[derive(Debug)]
+pub enum AllMessages {
+	/// Message for the validation subsystem.
+	CandidateValidation(CandidateValidationMessage),
+	/// Message for the candidate backing subsystem.
+	CandidateBacking(CandidateBackingMessage),
+	/// Message for the candidate selection subsystem.
+	CandidateSelection(CandidateSelectionMessage),
+	/// Message for the statement distribution subsystem.
+	StatementDistribution(StatementDistributionMessage),
+	/// Message for the availability distribution subsystem.
+	AvailabilityDistribution(AvailabilityDistributionMessage),
+	/// Message for the bitfield distribution subsystem.
+	BitfieldDistribution(BitfieldDistributionMessage),
+	/// Message for the Provisioner subsystem.
+	Provisioner(ProvisionerMessage),
+	/// Message for the Runtime API subsystem.
+	RuntimeApi(RuntimeApiMessage),
+	/// Message for the availability store subsystem.
+	AvailabilityStore(AvailabilityStoreMessage),
+}