Leverage sync state to accept txhashset (#1251)

Fixes #1246

p2p/src/peer.rs

@@ -428,6 +428,10 @@ impl ChainAdapter for TrackingAdapter {
 		self.adapter.txhashset_read(h)
 	}
 
+	fn txhashset_receive_ready(&self) -> bool {
+		self.adapter.txhashset_receive_ready()
+	}
+
 	fn txhashset_write(
 		&self,
 		h: Hash,

p2p/src/peers.rs

@@ -611,6 +611,10 @@ impl ChainAdapter for Peers {
 		self.adapter.txhashset_read(h)
 	}
 
+	fn txhashset_receive_ready(&self) -> bool {
+		self.adapter.txhashset_receive_ready()
+	}
+
 	fn txhashset_write(
 		&self,
 		h: Hash,

p2p/src/protocol.rs

@@ -233,6 +233,9 @@ impl MessageHandler for Protocol {
 					sm_arch.hash,
 					sm_arch.height,
 				);
+				if !self.adapter.txhashset_receive_ready() {
+					return Err(Error::BadMessage);
+				}
 
 				let mut tmp = env::temp_dir();
 				tmp.push("txhashset.zip");

p2p/src/serv.rs

@@ -250,6 +250,10 @@ impl ChainAdapter for DummyAdapter {
 		unimplemented!()
 	}
 
+	fn txhashset_receive_ready(&self) -> bool {
+		false
+	}
+
 	fn txhashset_write(
 		&self,
 		_h: Hash,

p2p/src/types.rs

@@ -256,6 +256,12 @@ pub trait ChainAdapter: Sync + Send {
 	/// at the provided block hash.
 	fn txhashset_read(&self, h: Hash) -> Option<TxHashSetRead>;
 
+	/// Whether the node is ready to accept a new txhashset. If this isn't the
+	/// case, the archive is provided without being requested and likely an
+	/// attack attempt. This should be checked *before* downloading the whole
+	/// state data.
+	fn txhashset_receive_ready(&self) -> bool;
+
 	/// Writes a reading view on a txhashset state that's been provided to us.
 	/// If we're willing to accept that new state, the data stream will be
 	/// read as a zip file, unzipped and the resulting state files should be