serve epoch signals over network and check them

ethcore/light/src/client/fetch.rs

@@ -16,9 +16,13 @@
 
 //! Trait for fetching chain data.
 
+use std::sync::Arc;
+
+use ethcore::engines::{Engine, StateDependentProof};
 use ethcore::header::Header;
 use ethcore::receipt::Receipt;
 use futures::future::IntoFuture;
+use util::H256;
 
 /// Provides full chain data.
 pub trait ChainDataFetcher: Send + Sync + 'static {
@@ -39,7 +43,7 @@ pub trait ChainDataFetcher: Send + Sync + 'static {
 	fn block_receipts(&self, header: &Header) -> Self::Receipts;
 
 	/// Fetch epoch transition proof at given header.
-	fn epoch_transition(&self, header: &Header) -> Self::Transition;
+	fn epoch_transition(&self, hash: H256, engine: Arc<Engine>, checker: Arc<StateDependentProof>) -> Self::Transition;
 }
 
 /// Fetcher implementation which cannot fetch anything.
@@ -63,7 +67,7 @@ impl ChainDataFetcher for Unavailable {
 		Err("fetching block receipts unavailable")
 	}
 
-	fn epoch_transition(&self, _header: &Header) -> Self::Body {
+	fn epoch_transition(&self, _h: H256, _e: Arc<Engine>, _check: Arc<StateDependentProof>) -> Self::Transition {
 		Err("fetching epoch transition proofs unavailable")
 	}
 }

ethcore/light/src/client/mod.rs

@@ -508,14 +508,11 @@ impl<T: ChainDataFetcher> Client<T> {
 		let proof = match proof {
 			Proof::Known(known) => known,
 			Proof::WithState(state_dependent) => {
-				loop {
-					let proof = self.fetcher.epoch_transition(header).into_future().wait()?;
-					match state_dependent.check_proof(&*self.engine, &proof) {
-						Ok(()) => break proof,
-						Err(e) =>
-							debug!(target: "client", "Fetched bad epoch transition proof from network: {}", e),
-					}
-				}
+				self.fetcher.epoch_transition(
+					header.hash(),
+					self.engine.clone(),
+					state_dependent
+				).into_future().wait()?
 			}
 		};