Reject existing tx

ethcore/src/client/client.rs

@@ -1060,6 +1060,10 @@ impl BlockChainClient for Client {
 		self.transaction_address(id).and_then(|address| self.chain.read().transaction(&address))
 	}
 
+	fn transaction_block(&self, id: TransactionID) -> Option<H256> {
+		self.transaction_address(id).map(|addr| addr.block_hash)
+	}
+
 	fn uncle(&self, id: UncleID) -> Option<Bytes> {
 		let index = id.position;
 		self.block_body(id.block).and_then(|body| BodyView::new(&body).uncle_rlp_at(index))

ethcore/src/client/test_client.rs

@@ -432,6 +432,10 @@ impl BlockChainClient for TestBlockChainClient {
 		None	// Simple default.
 	}
 
+	fn transaction_block(&self, _id: TransactionID) -> Option<H256> {
+		None	// Simple default.
+	}
+
 	fn uncle(&self, _id: UncleID) -> Option<Bytes> {
 		None	// Simple default.
 	}

ethcore/src/client/traits.rs

@@ -129,6 +129,9 @@ pub trait BlockChainClient : Sync + Send {
 	/// Get transaction with given hash.
 	fn transaction(&self, id: TransactionID) -> Option<LocalizedTransaction>;
 
+	/// Get the hash of block that contains the transaction, if any.
+	fn transaction_block(&self, id: TransactionID) -> Option<H256>;
+
 	/// Get uncle with given id.
 	fn uncle(&self, id: UncleID) -> Option<Bytes>;