Report the average network bandwidth (#1551)

* Report the average network bandwidth

* Fix concerns

substrate/core/network/src/service.rs

@@ -173,6 +173,18 @@ impl<B: BlockT + 'static, S: NetworkSpecialization<B>, H: ExHashT> Service<B, S,
 		Ok(service)
 	}
 
+	/// Returns the downloaded bytes per second averaged over the past few seconds.
+	#[inline]
+	pub fn average_download_per_sec(&self) -> u64 {
+		self.network.lock().average_download_per_sec()
+	}
+
+	/// Returns the uploaded bytes per second averaged over the past few seconds.
+	#[inline]
+	pub fn average_upload_per_sec(&self) -> u64 {
+		self.network.lock().average_upload_per_sec()
+	}
+
 	/// Called when a new block is imported by the client.
 	pub fn on_block_imported(&self, hash: B::Hash, header: &B::Header) {
 		self.handler.on_block_imported(&mut NetSyncIo::new(&self.network, self.protocol_id), hash, header)