Add support for mDNS (#2153)

* Use libp2p 0.6.0 instead of a custom branch

* Add support for mDNS

* Fix tests

* Nit

substrate/core/cli/src/lib.rs

@@ -359,6 +359,8 @@ fn fill_network_configuration(
 	config.in_peers = cli.in_peers;
 	config.out_peers = cli.out_peers;
 
+	config.enable_mdns = !cli.no_mdns;
+
 	Ok(())
 }
 

substrate/core/cli/src/params.rs

@@ -118,6 +118,11 @@ pub struct NetworkConfigurationParams {
 	#[structopt(long = "in-peers", value_name = "IN_PEERS", default_value = "25")]
 	pub in_peers: u32,
 
+	/// By default, the network will use mDNS to discover other nodes on the local network. This
+	/// disables it.
+	#[structopt(long = "no-mdns")]
+	pub no_mdns: bool,
+
 	#[allow(missing_docs)]
 	#[structopt(flatten)]
 	pub node_key_params: NodeKeyParams

substrate/core/network-libp2p/src/behaviour.rs

@@ -20,8 +20,10 @@ use libp2p::NetworkBehaviour;
 use libp2p::core::{Multiaddr, PeerId, ProtocolsHandler, PublicKey};
 use libp2p::core::swarm::{ConnectedPoint, NetworkBehaviour, NetworkBehaviourAction};
 use libp2p::core::swarm::{NetworkBehaviourEventProcess, PollParameters};
+use libp2p::core::swarm::toggle::Toggle;
 use libp2p::identify::{Identify, IdentifyEvent, protocol::IdentifyInfo};
 use libp2p::kad::{Kademlia, KademliaOut};
+use libp2p::mdns::{Mdns, MdnsEvent};
 use libp2p::ping::{Ping, PingEvent};
 use log::{debug, trace, warn};
 use std::{cmp, io, fmt, time::Duration, time::Instant};
@@ -41,6 +43,8 @@ pub struct Behaviour<TMessage, TSubstream> {
 	discovery: DiscoveryBehaviour<TSubstream>,
 	/// Periodically identifies the remote and responds to incoming requests.
 	identify: Identify<TSubstream>,
+	/// Discovers nodes on the local network.
+	mdns: Toggle<Mdns<TSubstream>>,
 
 	/// Queue of events to produce for the outside.
 	#[behaviour(ignore)]
@@ -55,6 +59,7 @@ impl<TMessage, TSubstream> Behaviour<TMessage, TSubstream> {
 		protocol: RegisteredProtocol<TMessage>,
 		known_addresses: Vec<(PeerId, Multiaddr)>,
 		peerset: substrate_peerset::PeersetMut,
+		enable_mdns: bool,
 	) -> Self {
 		let identify = {
 			let proto_version = "/substrate/1.0".to_string();
@@ -78,6 +83,17 @@ impl<TMessage, TSubstream> Behaviour<TMessage, TSubstream> {
 				duration_to_next_kad: Duration::from_secs(1),
 			},
 			identify,
+			mdns: if enable_mdns {
+				match Mdns::new() {
+					Ok(mdns) => Some(mdns).into(),
+					Err(err) => {
+						warn!(target: "sub-libp2p", "Failed to initialize mDNS: {:?}", err);
+						None.into()
+					}
+				}
+			} else {
+				None.into()
+			},
 			events: Vec::new(),
 		}
 	}
@@ -283,6 +299,19 @@ impl<TMessage, TSubstream> NetworkBehaviourEventProcess<PingEvent> for Behaviour
 	}
 }
 
+impl<TMessage, TSubstream> NetworkBehaviourEventProcess<MdnsEvent> for Behaviour<TMessage, TSubstream> {
+	fn inject_event(&mut self, event: MdnsEvent) {
+		match event {
+			MdnsEvent::Discovered(list) => {
+				for (peer_id, _) in list {
+					self.custom_protocols.add_discovered_node(&peer_id);
+				}
+			},
+			MdnsEvent::Expired(_) => {}
+		}
+	}
+}
+
 impl<TMessage, TSubstream> Behaviour<TMessage, TSubstream> {
 	fn poll<TEv>(&mut self) -> Async<NetworkBehaviourAction<TEv, BehaviourOut<TMessage>>> {
 		if !self.events.is_empty() {

substrate/core/network-libp2p/src/config.rs

@@ -48,6 +48,9 @@ pub struct NetworkConfiguration {
 	pub client_version: String,
 	/// Name of the node. Sent over the wire for debugging purposes.
 	pub node_name: String,
+	/// If true, the network will use mDNS to discover other libp2p nodes on the local network
+	/// and connect to them if they support the same chain.
+	pub enable_mdns: bool,
 }
 
 impl Default for NetworkConfiguration {
@@ -65,6 +68,7 @@ impl Default for NetworkConfiguration {
 			non_reserved_mode: NonReservedPeerMode::Accept,
 			client_version: "unknown".into(),
 			node_name: "unknown".into(),
+			enable_mdns: false,
 		}
 	}
 }

substrate/core/network-libp2p/src/service_task.rs

@@ -88,7 +88,7 @@ where TMessage: CustomMessage + Send + 'static {
 	// Build the swarm.
 	let (mut swarm, bandwidth) = {
 		let user_agent = format!("{} ({})", config.client_version, config.node_name);
-		let behaviour = Behaviour::new(user_agent, local_public, registered_custom, known_addresses, peerset_receiver);
+		let behaviour = Behaviour::new(user_agent, local_public, registered_custom, known_addresses, peerset_receiver, config.enable_mdns);
 		let (transport, bandwidth) = transport::build_transport(local_identity);
 		(Swarm::new(transport, behaviour, local_peer_id.clone()), bandwidth)
 	};

substrate/core/service/test/src/lib.rs

@@ -99,6 +99,7 @@ fn node_config<F: ServiceFactory> (
 		non_reserved_mode: NonReservedPeerMode::Accept,
 		client_version: "network/test/0.1".to_owned(),
 		node_name: "unknown".to_owned(),
+		enable_mdns: false,
 	};
 
 	Configuration {