From e8619399f254ac301db7591ddb6c5905347960e7 Mon Sep 17 00:00:00 2001
From: Age Manning <Age@AgeManning.com>
Date: Sun, 8 Sep 2019 07:10:36 +1000
Subject: [PATCH] Patch to correct for single byte RPC responses

---
 beacon_node/eth2-libp2p/src/rpc/codec/base.rs |  8 +++++---
 beacon_node/eth2-libp2p/src/rpc/codec/ssz.rs  | 10 +++++++---
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/beacon_node/eth2-libp2p/src/rpc/codec/base.rs b/beacon_node/eth2-libp2p/src/rpc/codec/base.rs
index a8a239867..973567473 100644
--- a/beacon_node/eth2-libp2p/src/rpc/codec/base.rs
+++ b/beacon_node/eth2-libp2p/src/rpc/codec/base.rs
@@ -101,13 +101,15 @@ where
     type Error = <TCodec as Decoder>::Error;
 
     fn decode(&mut self, src: &mut BytesMut) -> Result<Option<Self::Item>, Self::Error> {
+        // if we have only received the response code, wait for more bytes
+        if src.len() == 1 {
+            return Ok(None);
+        }
+        // using the response code determine which kind of payload needs to be decoded.
         let response_code = {
             if let Some(resp_code) = self.response_code {
                 resp_code
             } else {
-                // buffer should not be empty
-                debug_assert!(!src.is_empty());
-
                 let resp_byte = src.split_to(1);
                 let mut resp_code_byte = [0; 1];
                 resp_code_byte.copy_from_slice(&resp_byte);
diff --git a/beacon_node/eth2-libp2p/src/rpc/codec/ssz.rs b/beacon_node/eth2-libp2p/src/rpc/codec/ssz.rs
index 1966bab62..d0e4d01cf 100644
--- a/beacon_node/eth2-libp2p/src/rpc/codec/ssz.rs
+++ b/beacon_node/eth2-libp2p/src/rpc/codec/ssz.rs
@@ -4,7 +4,7 @@ use crate::rpc::{
     protocol::{ProtocolId, RPCError},
 };
 use crate::rpc::{ErrorMessage, RPCErrorResponse, RPCRequest, RPCResponse};
-use bytes::{Bytes, BytesMut};
+use bytes::{BufMut, Bytes, BytesMut};
 use ssz::{Decode, Encode};
 use tokio::codec::{Decoder, Encoder};
 use unsigned_varint::codec::UviBytes;
@@ -56,6 +56,10 @@ impl Encoder for SSZInboundCodec {
                 .inner
                 .encode(Bytes::from(bytes), dst)
                 .map_err(RPCError::from);
+        } else {
+            // payload is empty, add a 0-byte length prefix
+            dst.reserve(1);
+            dst.put_u8(0);
         }
         Ok(())
     }
@@ -152,8 +156,8 @@ impl Decoder for SSZOutboundCodec {
     type Error = RPCError;
 
     fn decode(&mut self, src: &mut BytesMut) -> Result<Option<Self::Item>, Self::Error> {
-        if src.is_empty() {
-            // the object sent could be empty. We return the empty object if this is the case
+        if src.len() == 1 && src[0] == 0_u8 {
+            // the object is empty. We return the empty object if this is the case
             match self.protocol.message_name.as_str() {
                 "hello" => match self.protocol.version.as_str() {
                     "1" => Err(RPCError::Custom(