light: give free credits for reserved peers (#9448)

* light: give free credits for reserved peers

* Fix ethcore-light tests

* Test free_flow_params

ethcore/light/src/net/context.rs

@@ -44,6 +44,9 @@ pub trait IoContext {
 
 	/// Persistent peer id
 	fn persistent_peer_id(&self, peer: PeerId) -> Option<NodeId>;
+
+	/// Whether given peer id is reserved peer
+	fn is_reserved_peer(&self, peer: PeerId) -> bool;
 }
 
 impl<T> IoContext for T where T: ?Sized + NetworkContext {
@@ -76,6 +79,10 @@ impl<T> IoContext for T where T: ?Sized + NetworkContext {
 	fn persistent_peer_id(&self, peer: PeerId) -> Option<NodeId> {
 		self.session_info(peer).and_then(|info| info.id)
 	}
+
+	fn is_reserved_peer(&self, peer: PeerId) -> bool {
+		NetworkContext::is_reserved_peer(self, peer)
+	}
 }
 
 /// Basic context for the protocol.

ethcore/light/src/net/mod.rs

@@ -354,6 +354,7 @@ pub struct LightProtocol {
 	peers: RwLock<PeerMap>,
 	capabilities: RwLock<Capabilities>,
 	flow_params: RwLock<Arc<FlowParams>>,
+	free_flow_params: Arc<FlowParams>,
 	handlers: Vec<Arc<Handler>>,
 	req_id: AtomicUsize,
 	sample_store: Box<SampleStore>,
@@ -383,6 +384,7 @@ impl LightProtocol {
 			peers: RwLock::new(HashMap::new()),
 			capabilities: RwLock::new(params.capabilities),
 			flow_params: RwLock::new(Arc::new(flow_params)),
+			free_flow_params: Arc::new(FlowParams::free()),
 			handlers: Vec::new(),
 			req_id: AtomicUsize::new(0),
 			sample_store,
@@ -706,8 +708,13 @@ impl LightProtocol {
 		};
 
 		let capabilities = self.capabilities.read();
-		let local_flow = self.flow_params.read();
-		let status_packet = status::write_handshake(&status, &capabilities, Some(&**local_flow));
+		let cost_local_flow = self.flow_params.read();
+		let local_flow = if io.is_reserved_peer(peer) {
+			&*self.free_flow_params
+		} else {
+			&**cost_local_flow
+		};
+		let status_packet = status::write_handshake(&status, &capabilities, Some(local_flow));
 
 		self.pending_peers.write().insert(peer, PendingPeer {
 			sent_head: chain_info.best_block_hash,
@@ -818,7 +825,11 @@ impl LightProtocol {
 		}
 
 		let remote_flow = flow_params.map(|params| (params.create_credits(), params));
-		let local_flow = self.flow_params.read().clone();
+		let local_flow = if io.is_reserved_peer(peer) {
+			self.free_flow_params.clone()
+		} else {
+			self.flow_params.read().clone()
+		};
 
 		self.peers.write().insert(peer, Mutex::new(Peer {
 			local_credits: local_flow.create_credits(),

ethcore/light/src/net/tests/mod.rs

@@ -87,6 +87,10 @@ impl IoContext for Expect {
 	fn persistent_peer_id(&self, _peer: PeerId) -> Option<NodeId> {
 		None
 	}
+
+	fn is_reserved_peer(&self, peer: PeerId) -> bool {
+		peer == 0xff
+	}
 }
 
 // can't implement directly for Arc due to cross-crate orphan rules.
@@ -190,6 +194,10 @@ fn write_handshake(status: &Status, capabilities: &Capabilities, proto: &LightPr
 	::net::status::write_handshake(status, capabilities, Some(&*flow_params))
 }
 
+fn write_free_handshake(status: &Status, capabilities: &Capabilities, proto: &LightProtocol) -> Vec<u8> {
+	::net::status::write_handshake(status, capabilities, Some(&proto.free_flow_params))
+}
+
 // helper for setting up the protocol handler and provider.
 fn setup(capabilities: Capabilities) -> (Arc<TestProviderInner>, LightProtocol) {
 	let provider = Arc::new(TestProviderInner {
@@ -231,6 +239,19 @@ fn handshake_expected() {
 	proto.on_connect(1, &Expect::Send(1, packet::STATUS, packet_body));
 }
 
+#[test]
+fn reserved_handshake_expected() {
+	let capabilities = capabilities();
+
+	let (provider, proto) = setup(capabilities);
+
+	let status = status(provider.client.chain_info());
+
+	let packet_body = write_free_handshake(&status, &capabilities, &proto);
+
+	proto.on_connect(0xff, &Expect::Send(0xff, packet::STATUS, packet_body));
+}
+
 #[test]
 #[should_panic]
 fn genesis_mismatch() {

ethcore/sync/src/light_sync/tests/test_net.rs

@@ -68,6 +68,7 @@ impl<'a> IoContext for TestIoContext<'a> {
 	fn protocol_version(&self, _peer: PeerId) -> Option<u8> { Some(::light::net::MAX_PROTOCOL_VERSION) }
 
 	fn persistent_peer_id(&self, _peer: PeerId) -> Option<NodeId> { unimplemented!() }
+	fn is_reserved_peer(&self, _peer: PeerId) -> bool { false }
 }
 
 // peer-specific data.

util/network-devp2p/src/host.rs

@@ -102,7 +102,7 @@ pub struct NetworkContext<'s> {
 	sessions: Arc<RwLock<Slab<SharedSession>>>,
 	session: Option<SharedSession>,
 	session_id: Option<StreamToken>,
-	_reserved_peers: &'s HashSet<NodeId>,
+	reserved_peers: &'s HashSet<NodeId>,
 }
 
 impl<'s> NetworkContext<'s> {
@@ -121,7 +121,7 @@ impl<'s> NetworkContext<'s> {
 			session_id: id,
 			session,
 			sessions,
-			_reserved_peers: reserved_peers,
+			reserved_peers: reserved_peers,
 		}
 	}
 
@@ -190,6 +190,13 @@ impl<'s> NetworkContextTrait for NetworkContext<'s> {
 	}
 
 	fn subprotocol_name(&self) -> ProtocolId { self.protocol }
+
+	fn is_reserved_peer(&self, peer: PeerId) -> bool {
+		self.session_info(peer)
+			.and_then(|info| info.id)
+			.map(|node| self.reserved_peers.contains(&node))
+			.unwrap_or(false)
+	}
 }
 
 /// Shared host information

util/network/src/lib.rs

@@ -285,6 +285,9 @@ pub trait NetworkContext {
 
 	/// Returns this object's subprotocol name.
 	fn subprotocol_name(&self) -> ProtocolId;
+
+	/// Returns whether the given peer ID is a reserved peer.
+	fn is_reserved_peer(&self, peer: PeerId) -> bool;
 }
 
 impl<'a, T> NetworkContext for &'a T where T: ?Sized + NetworkContext {
@@ -331,6 +334,10 @@ impl<'a, T> NetworkContext for &'a T where T: ?Sized + NetworkContext {
 	fn subprotocol_name(&self) -> ProtocolId {
 		(**self).subprotocol_name()
 	}
+
+	fn is_reserved_peer(&self, peer: PeerId) -> bool {
+		(**self).is_reserved_peer(peer)
+	}
 }
 
 /// Network IO protocol handler. This needs to be implemented for each new subprotocol.