Clean-ups in the network-gossip crate (#4542)

* Remove usage of sc_network::Context trait

* Remove Context::send_consensus

* Pass &mut dyn Network instead of &dyn Network

* Move Validator traits and related to separate module

substrate/client/network-gossip/src/validator.rs

@@ -0,0 +1,103 @@
+// Copyright 2017-2020 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate 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.
+
+// Substrate 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 Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+use sc_network::{config::Roles, PeerId};
+use sp_runtime::traits::Block as BlockT;
+
+/// Validates consensus messages.
+pub trait Validator<B: BlockT>: Send + Sync {
+	/// New peer is connected.
+	fn new_peer(&self, _context: &mut dyn ValidatorContext<B>, _who: &PeerId, _roles: Roles) {
+	}
+
+	/// New connection is dropped.
+	fn peer_disconnected(&self, _context: &mut dyn ValidatorContext<B>, _who: &PeerId) {
+	}
+
+	/// Validate consensus message.
+	fn validate(
+		&self,
+		context: &mut dyn ValidatorContext<B>,
+		sender: &PeerId,
+		data: &[u8]
+	) -> ValidationResult<B::Hash>;
+
+	/// Produce a closure for validating messages on a given topic.
+	fn message_expired<'a>(&'a self) -> Box<dyn FnMut(B::Hash, &[u8]) -> bool + 'a> {
+		Box::new(move |_topic, _data| false)
+	}
+
+	/// Produce a closure for filtering egress messages.
+	fn message_allowed<'a>(&'a self) -> Box<dyn FnMut(&PeerId, MessageIntent, &B::Hash, &[u8]) -> bool + 'a> {
+		Box::new(move |_who, _intent, _topic, _data| true)
+	}
+}
+
+/// Validation context. Allows reacting to incoming messages by sending out further messages.
+pub trait ValidatorContext<B: BlockT> {
+	/// Broadcast all messages with given topic to peers that do not have it yet.
+	fn broadcast_topic(&mut self, topic: B::Hash, force: bool);
+	/// Broadcast a message to all peers that have not received it previously.
+	fn broadcast_message(&mut self, topic: B::Hash, message: Vec<u8>, force: bool);
+	/// Send addressed message to a peer.
+	fn send_message(&mut self, who: &PeerId, message: Vec<u8>);
+	/// Send all messages with given topic to a peer.
+	fn send_topic(&mut self, who: &PeerId, topic: B::Hash, force: bool);
+}
+
+/// The reason for sending out the message.
+#[derive(Eq, PartialEq, Copy, Clone)]
+#[cfg_attr(test, derive(Debug))]
+pub enum MessageIntent {
+	/// Requested broadcast.
+	Broadcast,
+	/// Requested broadcast to all peers.
+	ForcedBroadcast,
+	/// Periodic rebroadcast of all messages to all peers.
+	PeriodicRebroadcast,
+}
+
+/// Message validation result.
+pub enum ValidationResult<H> {
+	/// Message should be stored and propagated under given topic.
+	ProcessAndKeep(H),
+	/// Message should be processed, but not propagated.
+	ProcessAndDiscard(H),
+	/// Message should be ignored.
+	Discard,
+}
+
+/// A gossip message validator that discards all messages.
+pub struct DiscardAll;
+
+impl<B: BlockT> Validator<B> for DiscardAll {
+	fn validate(
+		&self,
+		_context: &mut dyn ValidatorContext<B>,
+		_sender: &PeerId,
+		_data: &[u8],
+	) -> ValidationResult<B::Hash> {
+		ValidationResult::Discard
+	}
+
+	fn message_expired<'a>(&'a self) -> Box<dyn FnMut(B::Hash, &[u8]) -> bool + 'a> {
+		Box::new(move |_topic, _data| true)
+	}
+
+	fn message_allowed<'a>(&'a self) -> Box<dyn FnMut(&PeerId, MessageIntent, &B::Hash, &[u8]) -> bool + 'a> {
+		Box::new(move |_who, _intent, _topic, _data| false)
+	}
+}