Adds basic inbound/outbound upgrades for eth2 rpc

beacon_node/eth2-libp2p/src/rpc/methods.rs

@@ -2,39 +2,7 @@
 
 use ssz::{impl_decode_via_from, impl_encode_via_from};
 use ssz_derive::{Decode, Encode};
-use types::{BeaconBlockBody, BeaconBlockHeader, Epoch, Hash256, Slot};
-
-#[derive(Debug)]
-/// Available Serenity Libp2p RPC methods
-pub enum RPCMethod {
-    /// Initialise handshake between connecting peers.
-    Hello,
-    /// Terminate a connection providing a reason.
-    Goodbye,
-    /// Requests a number of beacon block roots.
-    BeaconBlockRoots,
-    /// Requests a number of beacon block headers.
-    BeaconBlockHeaders,
-    /// Requests a number of beacon block bodies.
-    BeaconBlockBodies,
-    /// Requests values for a merkle proof for the current blocks state root.
-    BeaconChainState, // Note: experimental, not complete.
-    /// Unknown method received.
-    Unknown,
-}
-
-pub enum RawRPCRequest
-
-
-#[derive(Debug, Clone)]
-pub enum RPCRequest {
-    Hello(HelloMessage),
-    Goodbye(GoodbyeReason),
-    BeaconBlockRoots(BeaconBlockRootsRequest),
-    BeaconBlockHeaders(BeaconBlockHeadersRequest),
-    BeaconBlockBodies(BeaconBlockBodiesRequest),
-    BeaconChainState(BeaconChainStateRequest),
-}
+use types::{Epoch, Hash256, Slot};
 
 #[derive(Debug, Clone)]
 pub enum RPCResponse {
@@ -45,19 +13,35 @@ pub enum RPCResponse {
     BeaconChainState(BeaconChainStateResponse),
 }
 
+pub enum ResponseCode {
+    Success = 0,
+    EncodingError = 1,
+    InvalidRequest = 2,
+    ServerError = 3,
+}
+
 /* Request/Response data structures for RPC methods */
 
+/* Requests */
+
 /// The HELLO request/response handshake message.
 #[derive(Encode, Decode, Clone, Debug)]
 pub struct HelloMessage {
     /// The network ID of the peer.
     pub network_id: u8,
+
+    /// The chain id for the HELLO request.
+    pub chain_id: u64,
+
     /// The peers last finalized root.
     pub latest_finalized_root: Hash256,
+
     /// The peers last finalized epoch.
     pub latest_finalized_epoch: Epoch,
+
     /// The peers last block root.
     pub best_root: Hash256,
+
     /// The peers last slot.
     pub best_slot: Slot,
 }
@@ -68,43 +52,40 @@ pub struct HelloMessage {
 /// however `GoodbyeReason::Unknown.into()` will go into `0_u64`. Therefore de-serializing then
 /// re-serializing may not return the same bytes.
 #[derive(Debug, Clone)]
-pub enum GoodbyeReason {
-    ClientShutdown,
-    IrreleventNetwork,
-    Fault,
-    Unknown,
+pub enum Goodbye {
+    /// This node has shutdown.
+    ClientShutdown = 1,
+
+    /// Incompatible networks.
+    IrreleventNetwork = 2,
+
+    /// Error/fault in the RPC.
+    Fault = 3,
+
+    /// Unknown reason.
+    Unknown = 0,
 }
 
-impl From<u64> for GoodbyeReason {
-    fn from(id: u64) -> GoodbyeReason {
+impl From<u64> for Goodbye {
+    fn from(id: u64) -> Goodbye {
         match id {
-            1 => GoodbyeReason::ClientShutdown,
-            2 => GoodbyeReason::IrreleventNetwork,
-            3 => GoodbyeReason::Fault,
-            _ => GoodbyeReason::Unknown,
+            1 => Goodbye::ClientShutdown,
+            2 => Goodbye::IrreleventNetwork,
+            3 => Goodbye::Fault,
+            _ => Goodbye::Unknown,
         }
     }
 }
 
-impl Into<u64> for GoodbyeReason {
-    fn into(self) -> u64 {
-        match self {
-            GoodbyeReason::Unknown => 0,
-            GoodbyeReason::ClientShutdown => 1,
-            GoodbyeReason::IrreleventNetwork => 2,
-            GoodbyeReason::Fault => 3,
-        }
-    }
-}
-
-impl_encode_via_from!(GoodbyeReason, u64);
-impl_decode_via_from!(GoodbyeReason, u64);
+impl_encode_via_from!(Goodbye, u64);
+impl_decode_via_from!(Goodbye, u64);
 
 /// Request a number of beacon block roots from a peer.
 #[derive(Encode, Decode, Clone, Debug, PartialEq)]
 pub struct BeaconBlockRootsRequest {
     /// The starting slot of the requested blocks.
     pub start_slot: Slot,
+
     /// The number of blocks from the start slot.
     pub count: u64, // this must be less than 32768. //TODO: Enforce this in the lower layers
 }
@@ -116,6 +97,17 @@ pub struct BeaconBlockRootsResponse {
     pub roots: Vec<BlockRootSlot>,
 }
 
+/// Contains a block root and associated slot.
+#[derive(Encode, Decode, Clone, Debug, PartialEq)]
+pub struct BlockRootSlot {
+    /// The block root.
+    pub block_root: Hash256,
+
+    /// The block slot.
+    pub slot: Slot,
+}
+
+/// The response of a beacl block roots request.
 impl BeaconBlockRootsResponse {
     /// Returns `true` if each `self.roots.slot[i]` is higher than the preceding `i`.
     pub fn slots_are_ascending(&self) -> bool {
@@ -129,33 +121,27 @@ impl BeaconBlockRootsResponse {
     }
 }
 
-/// Contains a block root and associated slot.
-#[derive(Encode, Decode, Clone, Debug, PartialEq)]
-pub struct BlockRootSlot {
-    /// The block root.
-    pub block_root: Hash256,
-    /// The block slot.
-    pub slot: Slot,
-}
-
 /// Request a number of beacon block headers from a peer.
 #[derive(Encode, Decode, Clone, Debug, PartialEq)]
 pub struct BeaconBlockHeadersRequest {
     /// The starting header hash of the requested headers.
     pub start_root: Hash256,
+
     /// The starting slot of the requested headers.
     pub start_slot: Slot,
+
     /// The maximum number of headers than can be returned.
     pub max_headers: u64,
+
     /// The maximum number of slots to skip between blocks.
     pub skip_slots: u64,
 }
 
 /// Response containing requested block headers.
-#[derive(Encode, Decode, Clone, Debug, PartialEq)]
+#[derive(Clone, Debug, PartialEq)]
 pub struct BeaconBlockHeadersResponse {
-    /// The list of requested beacon block headers.
-    pub headers: Vec<BeaconBlockHeader>,
+    /// The list of ssz-encoded requested beacon block headers.
+    pub headers: Vec<u8>,
 }
 
 /// Request a number of beacon block bodies from a peer.
@@ -166,10 +152,10 @@ pub struct BeaconBlockBodiesRequest {
 }
 
 /// Response containing the list of requested beacon block bodies.
-#[derive(Encode, Decode, Clone, Debug, PartialEq)]
+#[derive(Clone, Debug, PartialEq)]
 pub struct BeaconBlockBodiesResponse {
-    /// The list of beacon block bodies being requested.
-    pub block_bodies: Vec<BeaconBlockBody>,
+    /// The list of ssz-encoded beacon block bodies being requested.
+    pub block_bodies: Vec<u8>,
 }
 
 /// Request values for tree hashes which yield a blocks `state_root`.
@@ -184,5 +170,5 @@ pub struct BeaconChainStateRequest {
 #[derive(Encode, Decode, Clone, Debug, PartialEq)]
 pub struct BeaconChainStateResponse {
     /// The values corresponding the to the requested tree hashes.
-    pub values: bool, //TBD - stubbed with encodeable bool
+    pub values: bool, //TBD - stubbed with encodable bool
 }

beacon_node/eth2-libp2p/src/rpc/mod.rs

@@ -19,7 +19,7 @@ use slog::o;
 use std::marker::PhantomData;
 use tokio::io::{AsyncRead, AsyncWrite};
 
-/// This struct implements the libp2p `NetworkBehaviour` trait and therefore manages network-level
+/// Rpc implements the libp2p `NetworkBehaviour` trait and therefore manages network-level
 /// logic.
 pub struct Rpc<TSubstream> {
     /// Queue of events to processed.

beacon_node/eth2-libp2p/src/rpc/protocol.rs

@@ -1,14 +1,15 @@
 use super::methods::*;
 use libp2p::core::{upgrade, InboundUpgrade, OutboundUpgrade, UpgradeInfo};
-use ssz::{impl_decode_via_from, impl_encode_via_from, ssz_encode, Decode, Encode};
-use ssz_derive::{Decode, Encode};
-use std::hash::{Hash, Hasher};
+use ssz::{Decode, Encode};
+use std::hash::Hasher;
 use std::io;
 use std::iter;
 use tokio::io::{AsyncRead, AsyncWrite};
 
 /// The maximum bytes that can be sent across the RPC.
-const MAX_READ_SIZE: usize = 4_194_304; // 4M
+const MAX_RPC_SIZE: usize = 4_194_304; // 4M
+/// The protocol prefix the RPC protocol id.
+const PROTOCOL_PREFIX: &str = "/eth/serenity/rpc/";
 
 /// Implementation of the `ConnectionUpgrade` for the rpc protocol.
 #[derive(Debug, Clone)]
@@ -16,38 +17,25 @@ pub struct RPCProtocol;
 
 impl UpgradeInfo for RPCProtocol {
     type Info = &'static [u8];
-    type InfoIter = iter::Iter<Self::Info>;
+    type InfoIter = Vec<Self::Info>;
 
     fn protocol_info(&self) -> Self::InfoIter {
-        vec![b"/eth/serenity/rpc/hello/1/ssz", 
+        vec![
+            b"/eth/serenity/rpc/hello/1/ssz",
             b"/eth/serenity/rpc/goodbye/1/ssz",
             b"/eth/serenity/rpc/beacon_block_roots/1/ssz",
             b"/eth/serenity/rpc/beacon_block_headers/1/ssz",
             b"/eth/serenity/rpc/beacon_block_bodies/1/ssz",
-            b"/eth/serenity/rpc/beacon_chain_state/1/ssz"].into_iter()
+            b"/eth/serenity/rpc/beacon_chain_state/1/ssz",
+        ]
     }
 }
 
 /// The outbound RPC type as well as the return type used in the behaviour.
 #[derive(Debug, Clone)]
 pub enum RPCEvent {
-    Request ( RPCRequest ),
-    Response ( RPCResponse ), 
-}
-
-// outbound protocol supports the same as the inbound.
-impl UpgradeInfo for RPCEvent {
-    type Info = &'static [u8];
-    type InfoIter = iter::Iter<Self::Info>;
-
-    fn protocol_info(&self) -> Self::InfoIter {
-        vec![b"/eth/serenity/rpc/hello/1/ssz", 
-            b"/eth/serenity/rpc/goodbye/1/ssz", 
-            b"/eth/serenity/rpc/beacon_block_roots/1/ssz", 
-            b"/eth/serenity/rpc/beacon_block_headers/1/ssz", 
-            b"/eth/serenity/rpc/beacon_block_bodies/1/ssz", 
-            b"/eth/serenity/rpc/beacon_chain_state/1/ssz"].into_iter()
-    }
+    Request(RPCRequest),
+    Response(RPCResponse),
 }
 
 /* Inbound upgrade */
@@ -55,26 +43,169 @@ impl UpgradeInfo for RPCEvent {
 // The inbound protocol reads the request, decodes it and returns the stream to the protocol
 // handler to respond to once ready.
 
-type FnDecodeRPCEvent = fn(upgrade::Negotiated<TSocket>, Vec<u8>, ()) -> Result<(upgrade::Negotiated<TSocket>,RPCEvent), DecodeError>;
+type FnDecodeRPCEvent<TSocket> = fn(
+    upgrade::Negotiated<TSocket>,
+    Vec<u8>,
+    (),
+) -> Result<(upgrade::Negotiated<TSocket>, RPCEvent), RPCError>;
 
 impl<TSocket> InboundUpgrade<TSocket> for RPCProtocol
 where
     TSocket: AsyncRead + AsyncWrite,
 {
-    type Socket = upgrade::Negotiated<TSocket>,
-    type Output = (Self::Socket, RPCEvent),
-    type Error = DecodeError;
-    type Future = upgrade::ReadRespond<Self::Socket, (), FnDecodeRPCEvent>;
+    type Output = (upgrade::Negotiated<TSocket>, RPCEvent);
+    type Error = RPCError;
+    type Future = upgrade::ReadRespond<upgrade::Negotiated<TSocket>, (), FnDecodeRPCEvent<TSocket>>;
 
-    fn upgrade_inbound(self, socket: upgrade::Negotiated<TSocket>, protocol: Self::Info) -> Self::Future {
-        upgrade::read_respond(socket, MAX_READ_SIZE, (), |socket, packet, ()| Ok((socket, decode_request(packet, protocol)?)))
+    fn upgrade_inbound(
+        self,
+        socket: upgrade::Negotiated<TSocket>,
+        protocol: Self::Info,
+    ) -> Self::Future {
+        upgrade::read_respond(socket, MAX_RPC_SIZE, (), |socket, packet, ()| {
+            Ok((socket, decode_request(packet, protocol)?))
+        })
     }
 }
 
+/* Outbound request */
 
-/* Outbound upgrade */
+// Combines all the RPC requests into a single enum to implement `UpgradeInfo` and
+// `OutboundUpgrade`
 
-impl<TSocket> OutboundUpgrade<TSocket> for RPCEvent
+/// The raw protocol id sent over the wire.
+type RawProtocolId = Vec<u8>;
+
+/// Tracks the types in a protocol id.
+pub struct ProtocolId {
+    /// The rpc message type/name.
+    pub message_name: String,
+
+    /// The version of the RPC.
+    pub version: usize,
+
+    /// The encoding of the RPC.
+    pub encoding: String,
+}
+
+/// An RPC protocol ID.
+impl ProtocolId {
+    pub fn new(message_name: String, version: usize, encoding: String) -> Self {
+        ProtocolId {
+            message_name,
+            version,
+            encoding,
+        }
+    }
+
+    /// Converts a raw RPC protocol id string into an `RPCProtocolId`
+    pub fn from_bytes(bytes: Vec<u8>) -> Result<Self, RPCError> {
+        let protocol_string = String::from_utf8(bytes.as_vec())
+            .map_err(|_| RPCError::InvalidProtocol("Invalid protocol Id"))?;
+        let protocol_string = protocol_string.as_str().split('/');
+
+        Ok(ProtocolId {
+            message_name: protocol_string[3],
+            version: protocol_string[4],
+            encoding: protocol_string[5],
+        })
+    }
+}
+
+impl Into<RawProtocolId> for ProtocolId {
+    fn into(&self) -> [u8] {
+        &format!(
+            "{}/{}/{}/{}",
+            PROTOCOL_PREFIX, self.message_name, self.version, self.encoding
+        )
+        .as_bytes()
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum RPCRequest {
+    Hello(HelloMessage),
+    Goodbye(Goodbye),
+    BeaconBlockRoots(BeaconBlockRootsRequest),
+    BeaconBlockHeaders(BeaconBlockHeadersRequest),
+    BeaconBlockBodies(BeaconBlockBodiesRequest),
+    BeaconChainState(BeaconChainStateRequest),
+}
+
+impl UpgradeInfo for RPCRequest {
+    type Info = RawProtocolId;
+    type InfoIter = Vec<Self::Info>;
+
+    // add further protocols as we support more encodings/versions
+    fn protocol_info(&self) -> Self::InfoIter {
+        self.supported_protocols()
+    }
+}
+
+//  GOODBYE RPC has it's own upgrade as it doesn't expect a response
+impl UpgradeInfo for Goodbye {
+    type Info = RawProtocolId;
+    type InfoIter = iter::Once<Self::Info>;
+
+    // add further protocols as we support more encodings/versions
+    fn protocol_info(&self) -> Self::InfoIter {
+        iter::once(ProtocolId::new("goodbye", 1, "ssz").into())
+    }
+}
+
+/// Implements the encoding per supported protocol for RPCRequest.
+impl RPCRequest {
+    pub fn supported_protocols(&self) -> Vec<RawProtocolId> {
+        match self {
+            // add more protocols when versions/encodings are supported
+            RPCRequest::Hello(_) => vec![ProtocolId::new("hello", 1, "ssz").into()],
+            RPCRequest::Goodbye(_) => vec![ProtocolId::new("goodbye", 1, "ssz").into()],
+            RPCRequest::BeaconBlockRoots(_) => {
+                vec![ProtocolId::new("beacon_block_roots", 1, "ssz").into()]
+            }
+            RPCRequest::BeaconBlockHeaders(_) => {
+                vec![ProtocolId::new("beacon_block_headers", 1, "ssz").into()]
+            }
+            RPCRequest::BeaconBlockBodies(_) => {
+                vec![ProtocolId::new("beacon_block_bodies", 1, "ssz").into()]
+            }
+            RPCRequest::BeaconBlockState(_) => {
+                vec![ProtocolId::new("beacon_block_state", 1, "ssz").into()]
+            }
+        }
+    }
+
+    /// Encodes the Request object based on the negotiated protocol.
+    pub fn encode(&self, protocol: RawProtocolId) -> Result<Vec<u8>, io::Error> {
+        // Assume select has given a supported protocol.
+        let protocol = ProtocolId::from_bytes(protocol)?;
+        // Match on the encoding and in the future, the version
+        match protocol.encoding {
+            "ssz" => Ok(self.ssz_encode()),
+            _ => {
+                return Err(RPCError::Custom(format!(
+                    "Unknown Encoding: {}",
+                    protocol.encoding
+                )))
+            }
+        }
+    }
+
+    fn ssz_encode(&self) {
+        match self {
+            RPCRequest::Hello(req) => req.as_ssz_bytes(),
+            RPCRequest::Goodbye(req) => req.as_ssz_bytes(),
+            RPCRequest::BeaconBlockRoots(req) => req.as_ssz_bytes(),
+            RPCRequest::BeaconBlockHeaders(req) => req.as_ssz_bytes(),
+            RPCRequest::BeaconBlockBodies(req) => req.as_ssz_bytes(),
+            RPCRequest::BeaconChainState(req) => req.as_ssz_bytes(),
+        }
+    }
+}
+
+/* Outbound upgrades */
+
+impl<TSocket> OutboundUpgrade<TSocket> for RPCRequest
 where
     TSocket: AsyncWrite,
 {
@@ -82,177 +213,202 @@ where
     type Error = io::Error;
     type Future = upgrade::WriteOne<upgrade::Negotiated<TSocket>>;
 
-    #[inline]
-    fn upgrade_outbound(self, socket: upgrade::Negotiated<TSocket>, protocol: Self::Info) -> Self::Future {
-        let bytes = ssz_encode(&self);
-        upgrade::request_response(socket, 
+    fn upgrade_outbound(
+        self,
+        socket: upgrade::Negotiated<TSocket>,
+        protocol: Self::Info,
+    ) -> Self::Future {
+        let bytes = self.encode(protocol);
+        upgrade::request_response(socket, bytes, MAX_RPC_SIZE, protocol, |packet, protocol| {
+            Ok(decode_response(packet, protocol)?)
+        })
+    }
+}
+
+impl<TSocket> OutboundUpgrade<TSocket> for Goodbye
+where
+    TSocket: AsyncWrite,
+{
+    type Output = ();
+    type Error = io::Error;
+    type Future = upgrade::WriteOne<upgrade::Negotiated<TSocket>>;
+
+    fn upgrade_outbound(
+        self,
+        socket: upgrade::Negotiated<TSocket>,
+        protocol: Self::Info,
+    ) -> Self::Future {
+        let bytes = self.as_ssz_bytes();
         upgrade::write_one(socket, bytes)
     }
 }
 
+/* Decoding for Requests/Responses */
+
 // This function can be extended to provide further logic for supporting various protocol versions/encoding
-fn decode_request(packet: Vec<u8>, protocol: &'static[u8]) {
-    match protocol {
-        b"/eth/serenity/rpc/hello/1/ssz" => { }
-        b"/eth/serenity/rpc/goodbye/1/ssz", 
-        b"/eth/serenity/rpc/beacon_block_roots/1/ssz", 
-        b"/eth/serenity/rpc/beacon_block_headers/1/ssz", 
-        b"/eth/serenity/rpc/beacon_block_bodies/1/ssz", 
-        b"/eth/serenity/rpc/beacon_chain_state/1/ssz",
-        _=> { // Other protocols are not supported. 
-            return Err(DecodeError::UnknownProtocol); 
-        }
+fn decode_request(packet: Vec<u8>, protocol: ProtocolId) -> Result<RPCRequest, io::Error> {
+    let protocol_id = ProtocolId::from_bytes(protocol);
+
+    match protocol_id.message_name {
+        "hello" => match protocol_id.version {
+            "1" => match protocol_id.encoding {
+                "ssz" => Ok(RPCRequest::Hello(HelloMessage::from_ssz_bytes(&packet)?)),
+                _ => Err(RPCError::InvalidProtocol("Unknown HELLO encoding")),
+            },
+            _ => Err(RPCError::InvalidProtocol("Unknown HELLO version")),
+        },
+        "goodbye" => match protocol_id.version {
+            "1" => match protocol_id.encoding {
+                "ssz" => Ok(RPCRequest::Goodbye(Goodbye::from_ssz_bytes(&packet)?)),
+                _ => Err(RPCError::InvalidProtocol("Unknown GOODBYE encoding")),
+            },
+            _ => Err(RPCError::InvalidProtocol("Unknown GOODBYE version")),
+        },
+        "beacon_block_roots" => match protocol_id.version {
+            "1" => match protocol_id.encoding {
+                "ssz" => Ok(RPCRequest::BeaconBlockRooots(
+                    BeaconBlockRootsRequest::from_ssz_bytes(&packet)?,
+                )),
+                _ => Err(RPCError::InvalidProtocol(
+                    "Unknown BEACON_BLOCK_ROOTS encoding",
+                )),
+            },
+            _ => Err(RPCError::InvalidProtocol(
+                "Unknown BEACON_BLOCK_ROOTS version",
+            )),
+        },
+        "beacon_block_headers" => match protocol_id.version {
+            "1" => match protocol_id.encoding {
+                "ssz" => Ok(RPCRequest::BeaconBlockHeaders(
+                    BeaconBlockHeadersRequest::from_ssz_bytes(&packet),
+                )),
+                _ => Err(RPCError::InvalidProtocol(
+                    "Unknown BEACON_BLOCK_HEADERS encoding",
+                )),
+            },
+            _ => Err(RPCError::InvalidProtocol(
+                "Unknown BEACON_BLOCK_HEADERS version",
+            )),
+        },
+        "beacon_block_bodies" => match protocol_id.version {
+            "1" => match protocol_id.encoding {
+                "ssz" => Ok(RPCRequest::BeaconBlockBodies(
+                    BeaconBlockBodiesRequest::from_ssz_bytes(&packet)?,
+                )),
+                _ => Err(RPCError::InvalidProtocol(
+                    "Unknown BEACON_BLOCK_BODIES encoding",
+                )),
+            },
+            _ => Err(RPCError::InvalidProtocol(
+                "Unknown BEACON_BLOCK_BODIES version",
+            )),
+        },
+        "beacon_chain_state" => match protocol_id.version {
+            "1" => match protocol_id.encoding {
+                "ssz" => Ok(RPCRequest::BeaconChainState(
+                    BeaconChainStateRequest::from_ssz_bytes(&packet)?,
+                )),
+                _ => Err(RPCError::InvalidProtocol(
+                    "Unknown BEACON_CHAIN_STATE encoding",
+                )),
+            },
+            _ => Err(RPCError::InvalidProtocol(
+                "Unknown BEACON_CHAIN_STATE version",
+            )),
+        },
     }
 }
 
+/// Decodes a response that was received on the same stream as a request. The response type should
+/// therefore match the request protocol type.
+fn decode_response(packet: Vec<u8>, protocol: RawProtocolId) -> Result<RPCResponse, RPCError> {
+    let protocol_id = ProtocolId::from_bytes(protocol)?;
 
-
-
-
-
-
-
-
-
-
-
-
-
-/// A helper struct used to obtain SSZ serialization for RPC messages.
-#[derive(Encode, Decode, Default)]
-struct SszContainer {
-    /// Note: the `is_request` field is not included in the spec.
-    ///
-    /// We are unable to determine a request from a response unless we add some flag to the
-    /// packet. Here we have added a bool (encoded as 1 byte) which is set to `1` if the
-    /// message is a request.
-    is_request: bool,
-    id: u64,
-    other: u16,
-    bytes: Vec<u8>,
-}
-
-fn decode(packet: Vec<u8>) -> Result<RPCEvent, DecodeError> {
-    let msg = SszContainer::from_ssz_bytes(&packet)?;
-
-    if msg.is_request {
-        let body = match RPCMethod::from(msg.other) {
-            RPCMethod::Hello => RPCRequest::Hello(HelloMessage::from_ssz_bytes(&msg.bytes)?),
-            RPCMethod::Goodbye => RPCRequest::Goodbye(GoodbyeReason::from_ssz_bytes(&msg.bytes)?),
-            RPCMethod::BeaconBlockRoots => {
-                RPCRequest::BeaconBlockRoots(BeaconBlockRootsRequest::from_ssz_bytes(&msg.bytes)?)
-            }
-            RPCMethod::BeaconBlockHeaders => RPCRequest::BeaconBlockHeaders(
-                BeaconBlockHeadersRequest::from_ssz_bytes(&msg.bytes)?,
-            ),
-            RPCMethod::BeaconBlockBodies => {
-                RPCRequest::BeaconBlockBodies(BeaconBlockBodiesRequest::from_ssz_bytes(&msg.bytes)?)
-            }
-            RPCMethod::BeaconChainState => {
-                RPCRequest::BeaconChainState(BeaconChainStateRequest::from_ssz_bytes(&msg.bytes)?)
-            }
-            RPCMethod::Unknown => return Err(DecodeError::UnknownRPCMethod),
-        };
-
-        Ok(RPCEvent::Request {
-            id: RequestId::from(msg.id),
-            method_id: msg.other,
-            body,
-        })
-    }
-    // we have received a response
-    else {
-        let result = match RPCMethod::from(msg.other) {
-            RPCMethod::Hello => RPCResponse::Hello(HelloMessage::from_ssz_bytes(&msg.bytes)?),
-            RPCMethod::BeaconBlockRoots => {
-                RPCResponse::BeaconBlockRoots(BeaconBlockRootsResponse::from_ssz_bytes(&msg.bytes)?)
-            }
-            RPCMethod::BeaconBlockHeaders => RPCResponse::BeaconBlockHeaders(
-                BeaconBlockHeadersResponse::from_ssz_bytes(&msg.bytes)?,
-            ),
-            RPCMethod::BeaconBlockBodies => RPCResponse::BeaconBlockBodies(
-                BeaconBlockBodiesResponse::from_ssz_bytes(&msg.bytes)?,
-            ),
-            RPCMethod::BeaconChainState => {
-                RPCResponse::BeaconChainState(BeaconChainStateResponse::from_ssz_bytes(&msg.bytes)?)
-            }
-            // We should never receive a goodbye response; it is invalid.
-            RPCMethod::Goodbye => return Err(DecodeError::UnknownRPCMethod),
-            RPCMethod::Unknown => return Err(DecodeError::UnknownRPCMethod),
-        };
-
-        Ok(RPCEvent::Response {
-            id: RequestId::from(msg.id),
-            method_id: msg.other,
-            result,
-        })
-    }
-}
-
-
-impl Encode for RPCEvent {
-    fn is_ssz_fixed_len() -> bool {
-        false
-    }
-
-    fn ssz_append(&self, buf: &mut Vec<u8>) {
-        let container = match self {
-            RPCEvent::Request {
-                id,
-                method_id,
-                body,
-            } => SszContainer {
-                is_request: true,
-                id: (*id).into(),
-                other: *method_id,
-                bytes: match body {
-                    RPCRequest::Hello(body) => body.as_ssz_bytes(),
-                    RPCRequest::Goodbye(body) => body.as_ssz_bytes(),
-                    RPCRequest::BeaconBlockRoots(body) => body.as_ssz_bytes(),
-                    RPCRequest::BeaconBlockHeaders(body) => body.as_ssz_bytes(),
-                    RPCRequest::BeaconBlockBodies(body) => body.as_ssz_bytes(),
-                    RPCRequest::BeaconChainState(body) => body.as_ssz_bytes(),
-                },
-            },
-            RPCEvent::Response {
-                id,
-                method_id,
-                result,
-            } => SszContainer {
-                is_request: false,
-                id: (*id).into(),
-                other: *method_id,
-                bytes: match result {
-                    RPCResponse::Hello(response) => response.as_ssz_bytes(),
-                    RPCResponse::BeaconBlockRoots(response) => response.as_ssz_bytes(),
-                    RPCResponse::BeaconBlockHeaders(response) => response.as_ssz_bytes(),
-                    RPCResponse::BeaconBlockBodies(response) => response.as_ssz_bytes(),
-                    RPCResponse::BeaconChainState(response) => response.as_ssz_bytes(),
-                },
-            },
-        };
-
-        container.ssz_append(buf)
+    match protocol_id.message_name {
+        "hello" => match protocol_id.version {
+            "1" => match protocol_id.encoding {
+                "ssz" => Ok(RPCResponse::Hello(HelloMessage::from_ssz_bytes(&packet)?)),
+                _ => Err(RPCError::InvalidProtocol("Unknown HELLO encoding")),
+            },
+            _ => Err(RPCError::InvalidProtocol("Unknown HELLO version")),
+        },
+        "goodbye" => Err(RPCError::Custom("GOODBYE should not have a response")),
+        "beacon_block_roots" => match protocol_id.version {
+            "1" => match protocol_id.encoding {
+                "ssz" => Ok(RPCResponse::BeaconBlockRoots(
+                    BeaconBlockRootsResponse::from_ssz_bytes(&packet)?,
+                )),
+                _ => Err(RPCError::InvalidProtocol(
+                    "Unknown BEACON_BLOCK_ROOTS encoding",
+                )),
+            },
+            _ => Err(RPCError::InvalidProtocol(
+                "Unknown BEACON_BLOCK_ROOTS version",
+            )),
+        },
+        "beacon_block_headers" => match protocol_id.version {
+            "1" => match protocol_id.encoding {
+                "ssz" => Ok(RPCResponse::BeaconBlockHeaders(
+                    BeaconBlockHeadersResponse { headers: packet },
+                )),
+                _ => Err(RPCError::InvalidProtocol(
+                    "Unknown BEACON_BLOCK_HEADERS encoding",
+                )),
+            },
+            _ => Err(RPCError::InvalidProtocol(
+                "Unknown BEACON_BLOCK_HEADERS version",
+            )),
+        },
+        "beacon_block_bodies" => match protocol_id.version {
+            "1" => match protocol_id.encoding {
+                "ssz" => Ok(RPCResponse::BeaconBlockBodies(BeaconBlockBodiesResponse {
+                    block_bodies: packet,
+                })),
+                _ => Err(RPCError::InvalidProtocol(
+                    "Unknown BEACON_BLOCK_BODIES encoding",
+                )),
+            },
+            _ => Err(RPCError::InvalidProtocol(
+                "Unknown BEACON_BLOCK_BODIES version",
+            )),
+        },
+        "beacon_chain_state" => match protocol_id.version {
+            "1" => match protocol_id.encoding {
+                "ssz" => Ok(BeaconChainStateRequest::from_ssz_bytes(&packet)?),
+                _ => Err(RPCError::InvalidProtocol(
+                    "Unknown BEACON_CHAIN_STATE encoding",
+                )),
+            },
+            _ => Err(RPCError::InvalidProtocol(
+                "Unknown BEACON_CHAIN_STATE version",
+            )),
+        },
     }
 }
 
+/// Error in RPC Encoding/Decoding.
 #[derive(Debug)]
-pub enum DecodeError {
+pub enum RPCError {
+    /// Error when reading the packet from the socket.
     ReadError(upgrade::ReadOneError),
+    /// Error when decoding the raw buffer from ssz.
     SSZDecodeError(ssz::DecodeError),
-    UnknownRPCMethod,
+    /// Invalid Protocol ID
+    InvalidProtocol(&'static str),
+    /// Custom message.
+    Custom(String),
 }
 
-impl From<upgrade::ReadOneError> for DecodeError {
+impl From<upgrade::ReadOneError> for RPCError {
     #[inline]
     fn from(err: upgrade::ReadOneError) -> Self {
-        DecodeError::ReadError(err)
+        RPCError::ReadError(err)
     }
 }
 
-impl From<ssz::DecodeError> for DecodeError {
+impl From<ssz::DecodeError> for RPCError {
     #[inline]
     fn from(err: ssz::DecodeError) -> Self {
-        DecodeError::SSZDecodeError(err)
+        RPCError::SSZDecodeError(err)
     }
 }