Persist light client updates (#5545)

* persist light client updates

* update beacon chain to serve light client updates

* resolve todos

* cache best update

* extend cache parts

* is better light client update

* resolve merge conflict

* initial api changes

* add lc update db column

* fmt

* added tests

* add sim

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

* fix some weird issues with the simulator

* tests

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

* test changes

* merge conflict

* testing

* started work on ef tests and some code clean up

* update tests

* linting

* noop pre altair, were still failing on electra though

* allow for zeroed light client header

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

* merge unstable

* remove unwraps

* remove unwraps

* Update light_client_update.rs

* merge unstable

* move functionality to helper methods

* refactor is best update fn

* refactor is best update fn

* improve organization of light client server cache logic

* fork diget calc, and only spawn as many blcoks as we need for the lc update test

* fetch lc update from the cache if it exists

* fmt

* Fix beacon_chain tests

* Add debug code to update ranking_order ef test

* Fix compare code

* merge conflicts

* fix test

* Merge branch 'persist-light-client-updates' of https://github.com/eserilev/lighthouse into persist-light-client-updates

* Use blinded blocks for light client proofs

* fix ef test

* merge conflicts

* fix lc update check

* Lint

* resolve merge conflict

* Merge branch 'persist-light-client-updates' of https://github.com/eserilev/lighthouse into persist-light-client-updates

* revert basic sim

* small fix

* revert sim

* Review PR

* resolve merge conflicts

* Merge branch 'unstable' into persist-light-client-updates

common/eth2/src/lib.rs

@@ -763,6 +763,31 @@ impl BeaconNodeHttpClient {
         self.get_opt(path).await
     }
 
+    /// `GET beacon/light_client/updates`
+    ///
+    /// Returns `Ok(None)` on a 404 error.
+    pub async fn get_beacon_light_client_updates<E: EthSpec>(
+        &self,
+        start_period: u64,
+        count: u64,
+    ) -> Result<Option<Vec<ForkVersionedResponse<LightClientUpdate<E>>>>, Error> {
+        let mut path = self.eth_path(V1)?;
+
+        path.path_segments_mut()
+            .map_err(|()| Error::InvalidUrl(self.server.clone()))?
+            .push("beacon")
+            .push("light_client")
+            .push("updates");
+
+        path.query_pairs_mut()
+            .append_pair("start_period", &start_period.to_string());
+
+        path.query_pairs_mut()
+            .append_pair("count", &count.to_string());
+
+        self.get_opt(path).await
+    }
+
     /// `GET beacon/light_client/bootstrap`
     ///
     /// Returns `Ok(None)` on a 404 error.

common/eth2/src/types.rs

@@ -784,6 +784,24 @@ pub struct ValidatorAggregateAttestationQuery {
     pub committee_index: Option<CommitteeIndex>,
 }
 
+#[derive(Clone, Deserialize)]
+pub struct LightClientUpdatesQuery {
+    pub start_period: u64,
+    pub count: u64,
+}
+
+#[derive(Encode, Decode)]
+pub struct LightClientUpdateSszResponse {
+    pub response_chunk_len: Vec<u8>,
+    pub response_chunk: Vec<u8>,
+}
+
+#[derive(Encode, Decode)]
+pub struct LightClientUpdateResponseChunk {
+    pub context: [u8; 4],
+    pub payload: Vec<u8>,
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, Hash)]
 pub struct BeaconCommitteeSubscription {
     #[serde(with = "serde_utils::quoted_u64")]