client/service: Deny block requests when light client

client/network/src/protocol/message.rs

@@ -388,7 +388,6 @@ pub mod generic {
 	/// Request block data from a peer.
 	#[derive(Debug, PartialEq, Eq, Clone, Encode, Decode)]
 	pub struct BlockRequest<Hash, Number> {
-		// TODO: Is this used anywhere?
 		/// Unique request id.
 		pub id: RequestId,
 		/// Bits of block data to request.

client/network/src/request_responses.rs

@@ -50,7 +50,6 @@ use libp2p::{
 };
 use std::{
 	borrow::Cow, collections::{hash_map::Entry, HashMap}, convert::TryFrom as _, io, iter,
-	// TODO: Should we use wasm_timer instant here?
 	pin::Pin, task::{Context, Poll}, time::{Duration, Instant},
 };
 

client/network/src/service/metrics.rs

@@ -78,8 +78,6 @@ pub struct Metrics {
 	pub requests_in_success_total: HistogramVec,
 	pub requests_out_failure_total: CounterVec<U64>,
 	pub requests_out_success_total: HistogramVec,
-	// TODO: Is this still used anywhere?
-	pub requests_out_started_total: CounterVec<U64>,
 }
 
 impl Metrics {
@@ -256,13 +254,6 @@ impl Metrics {
 				},
 				&["protocol"]
 			)?, registry)?,
-			requests_out_started_total: prometheus::register(CounterVec::new(
-				Opts::new(
-					"sub_libp2p_requests_out_started_total",
-					"Total number of requests emitted"
-				),
-				&["protocol"]
-			)?, registry)?,
 		})
 	}
 }

client/network/test/src/lib.rs

@@ -781,7 +781,7 @@ pub trait TestNetFactory: Sized {
 		});
 	}
 
-	// TODO: Not ideal. Can we do better?
+	/// Used to spawn background tasks, e.g. the block request protocol handler.
 	fn spawn_task(&self, f: BoxFuture<'static, ()>) {
 		async_std::task::spawn(f);
 	}

client/service/src/builder.rs

@@ -883,10 +883,15 @@ pub fn build_network<TBl, TExPool, TImpQu, TCl>(
 	};
 
 	let block_request_protocol_config = {
-		// TODO: Only do this if we are not a light client.
-		let (handler, protocol_config) = sc_network::block_request_handler::BlockRequestHandler::new(protocol_id.clone(), client.clone());
-		spawn_handle.spawn("block_request_handler", handler.run());
-		protocol_config
+		if config.role == Role::Light {
+			// Allow outgoing requests but deny incoming requests.
+			sc_network::block_request_handler::generate_protocol_config(protocol_id.clone())
+		} else {
+			// Allow both outgoing and incoming requests.
+			let (handler, protocol_config) = sc_network::block_request_handler::BlockRequestHandler::new(protocol_id.clone(), client.clone());
+			spawn_handle.spawn("block_request_handler", handler.run());
+			protocol_config
+		}
 	};
 
 	let network_params = sc_network::config::Params {