Light client updates by range RPC (#6383)

* enable lc update over rpc

* resolve TODOs

* resolve merge conflicts

* move max light client updates to eth spec

* Merge branch 'unstable' of https://github.com/sigp/lighthouse into light-client-updates-by-range-rpc

* remove ethspec dependency

* Update beacon_node/network/src/network_beacon_processor/rpc_methods.rs

Co-authored-by: Michael Sproul <micsproul@gmail.com>

* Update beacon_node/lighthouse_network/src/rpc/methods.rs

Co-authored-by: Michael Sproul <micsproul@gmail.com>

beacon_node/lighthouse_network/src/rpc/methods.rs

@@ -13,10 +13,11 @@ use std::sync::Arc;
 use strum::IntoStaticStr;
 use superstruct::superstruct;
 use types::blob_sidecar::BlobIdentifier;
+use types::light_client_update::MAX_REQUEST_LIGHT_CLIENT_UPDATES;
 use types::{
     blob_sidecar::BlobSidecar, ChainSpec, ColumnIndex, DataColumnIdentifier, DataColumnSidecar,
     Epoch, EthSpec, Hash256, LightClientBootstrap, LightClientFinalityUpdate,
-    LightClientOptimisticUpdate, RuntimeVariableList, SignedBeaconBlock, Slot,
+    LightClientOptimisticUpdate, LightClientUpdate, RuntimeVariableList, SignedBeaconBlock, Slot,
 };
 
 /// Maximum length of error message.
@@ -471,6 +472,34 @@ impl DataColumnsByRootRequest {
     }
 }
 
+/// Request a number of beacon data columns from a peer.
+#[derive(Encode, Decode, Clone, Debug, PartialEq)]
+pub struct LightClientUpdatesByRangeRequest {
+    /// The starting period to request light client updates.
+    pub start_period: u64,
+    /// The number of periods from `start_period`.
+    pub count: u64,
+}
+
+impl LightClientUpdatesByRangeRequest {
+    pub fn max_requested(&self) -> u64 {
+        MAX_REQUEST_LIGHT_CLIENT_UPDATES
+    }
+
+    pub fn ssz_min_len() -> usize {
+        LightClientUpdatesByRangeRequest {
+            start_period: 0,
+            count: 0,
+        }
+        .as_ssz_bytes()
+        .len()
+    }
+
+    pub fn ssz_max_len() -> usize {
+        Self::ssz_min_len()
+    }
+}
+
 /* RPC Handling and Grouping */
 // Collection of enums and structs used by the Codecs to encode/decode RPC messages
 
@@ -498,6 +527,9 @@ pub enum RpcSuccessResponse<E: EthSpec> {
     /// A response to a get LIGHT_CLIENT_FINALITY_UPDATE request.
     LightClientFinalityUpdate(Arc<LightClientFinalityUpdate<E>>),
 
+    /// A response to a get LIGHT_CLIENT_UPDATES_BY_RANGE request.
+    LightClientUpdatesByRange(Arc<LightClientUpdate<E>>),
+
     /// A response to a get BLOBS_BY_ROOT request.
     BlobsByRoot(Arc<BlobSidecar<E>>),
 
@@ -534,6 +566,9 @@ pub enum ResponseTermination {
 
     /// Data column sidecars by range stream termination.
     DataColumnsByRange,
+
+    /// Light client updates by range stream termination.
+    LightClientUpdatesByRange,
 }
 
 /// The structured response containing a result/code indicating success or failure
@@ -633,6 +668,7 @@ impl<E: EthSpec> RpcSuccessResponse<E> {
                 Protocol::LightClientOptimisticUpdate
             }
             RpcSuccessResponse::LightClientFinalityUpdate(_) => Protocol::LightClientFinalityUpdate,
+            RpcSuccessResponse::LightClientUpdatesByRange(_) => Protocol::LightClientUpdatesByRange,
         }
     }
 }
@@ -704,6 +740,13 @@ impl<E: EthSpec> std::fmt::Display for RpcSuccessResponse<E> {
                     update.signature_slot()
                 )
             }
+            RpcSuccessResponse::LightClientUpdatesByRange(update) => {
+                write!(
+                    f,
+                    "LightClientUpdatesByRange Slot: {}",
+                    update.signature_slot(),
+                )
+            }
         }
     }
 }