Add missing child trie rpc on_custom_message handler (#3522)

* missing on_custom for child read.

* fix and complete, add test cases.

* shorten line.

* replace vecs of key value tuple with maps.

substrate/core/network/src/chain.rs

@@ -51,6 +51,9 @@ pub trait Client<Block: BlockT>: Send + Sync {
 	/// Get storage read execution proof.
 	fn read_proof(&self, block: &Block::Hash, key: &[u8]) -> Result<Vec<Vec<u8>>, Error>;
 
+	/// Get child storage read execution proof.
+	fn read_child_proof(&self, block: &Block::Hash, storage_key: &[u8], key: &[u8]) -> Result<Vec<Vec<u8>>, Error>;
+
 	/// Get method execution proof.
 	fn execution_proof(&self, block: &Block::Hash, method: &str, data: &[u8]) -> Result<(Vec<u8>, Vec<Vec<u8>>), Error>;
 
@@ -113,6 +116,16 @@ impl<B, E, Block, RA> Client<Block> for SubstrateClient<B, E, Block, RA> where
 		(self as &SubstrateClient<B, E, Block, RA>).read_proof(&BlockId::Hash(block.clone()), key)
 	}
 
+	fn read_child_proof(
+		&self,
+		block: &Block::Hash,
+		storage_key: &[u8],
+		key: &[u8]
+	) -> Result<Vec<Vec<u8>>, Error> {
+		(self as &SubstrateClient<B, E, Block, RA>)
+			.read_child_proof(&BlockId::Hash(block.clone()), storage_key, key)
+	}
+
 	fn execution_proof(&self, block: &Block::Hash, method: &str, data: &[u8]) -> Result<(Vec<u8>, Vec<Vec<u8>>), Error> {
 		(self as &SubstrateClient<B, E, Block, RA>).execution_proof(&BlockId::Hash(block.clone()), method, data)
 	}

substrate/core/network/src/protocol.rs

@@ -547,7 +547,8 @@ impl<B: BlockT, S: NetworkSpecialization<B>, H: ExHashT> Protocol<B, S, H> {
 				self.on_finality_proof_request(who, request),
 			GenericMessage::FinalityProofResponse(response) =>
 				return self.on_finality_proof_response(who, response),
-			GenericMessage::RemoteReadChildRequest(_) => {}
+			GenericMessage::RemoteReadChildRequest(request) =>
+				self.on_remote_read_child_request(who, request),
 			GenericMessage::Consensus(msg) => {
 				if self.context_data.peers.get(&who).map_or(false, |peer| peer.info.protocol_version > 2) {
 					self.consensus_gossip.on_incoming(
@@ -1293,6 +1294,36 @@ impl<B: BlockT, S: NetworkSpecialization<B>, H: ExHashT> Protocol<B, S, H> {
 		);
 	}
 
+	fn on_remote_read_child_request(
+		&mut self,
+		who: PeerId,
+		request: message::RemoteReadChildRequest<B::Hash>,
+	) {
+		trace!(target: "sync", "Remote read child request {} from {} ({} {} at {})",
+			request.id, who, request.storage_key.to_hex::<String>(), request.key.to_hex::<String>(), request.block);
+		let proof = match self.context_data.chain.read_child_proof(&request.block, &request.storage_key, &request.key) {
+			Ok(proof) => proof,
+			Err(error) => {
+				trace!(target: "sync", "Remote read child request {} from {} ({} {} at {}) failed with: {}",
+					request.id,
+					who,
+					request.storage_key.to_hex::<String>(),
+					request.key.to_hex::<String>(),
+					request.block,
+					error
+				);
+				Default::default()
+			}
+		};
+		self.send_message(
+			who,
+			GenericMessage::RemoteReadResponse(message::RemoteReadResponse {
+				id: request.id,
+				proof,
+			}),
+		);
+	}
+
 	fn on_remote_read_response(
 		&mut self,
 		who: PeerId,