API for LightClientBootstrap, LightClientFinalityUpdate, LightClientOptimisticUpdate and light client events (#3954)

* rebase and add comment

* conditional test

* test

* optimistic chould be working now

* finality should be working now

* try again

* try again

* clippy fix

* add lc bootstrap beacon api

* add lc optimistic/finality update to events

* fmt

* That error isn't occuring on my computer but I think this should fix it

* Add missing test file

* Update light client types to comply with Altair light client spec.

* Fix test compilation

* Support deserializing light client structures for the Bellatrix fork

* Move `get_light_client_bootstrap` logic to `BeaconChain`. `LightClientBootstrap` API to return `ForkVersionedResponse`.

* Misc fixes.
- log cleanup
- move http_api config mutation to `config::get_config` for consistency
- fix light client API responses

* Add light client bootstrap API test and fix existing ones.

* Fix test for `light-client-server` http api config.

* Appease clippy

* Efficiency improvement when retrieving beacon state.

---------

Co-authored-by: Jimmy Chen <jchen.tc@gmail.com>

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -6446,6 +6446,39 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
     pub fn data_availability_boundary(&self) -> Option<Epoch> {
         self.data_availability_checker.data_availability_boundary()
     }
+
+    /// Gets the `LightClientBootstrap` object for a requested block root.
+    ///
+    /// Returns `None` when the state or block is not found in the database.
+    #[allow(clippy::type_complexity)]
+    pub fn get_light_client_bootstrap(
+        &self,
+        block_root: &Hash256,
+    ) -> Result<Option<(LightClientBootstrap<T::EthSpec>, ForkName)>, Error> {
+        let Some((state_root, slot)) = self
+            .get_blinded_block(block_root)?
+            .map(|block| (block.state_root(), block.slot()))
+        else {
+            return Ok(None);
+        };
+
+        let Some(mut state) = self.get_state(&state_root, Some(slot))? else {
+            return Ok(None);
+        };
+
+        let fork_name = state
+            .fork_name(&self.spec)
+            .map_err(Error::InconsistentFork)?;
+
+        match fork_name {
+            ForkName::Altair | ForkName::Merge => {
+                LightClientBootstrap::from_beacon_state(&mut state)
+                    .map(|bootstrap| Some((bootstrap, fork_name)))
+                    .map_err(Error::LightClientError)
+            }
+            ForkName::Base | ForkName::Capella | ForkName::Deneb => Err(Error::UnsupportedFork),
+        }
+    }
 }
 
 impl<T: BeaconChainTypes> Drop for BeaconChain<T> {

beacon_node/beacon_chain/src/errors.rs

@@ -221,6 +221,8 @@ pub enum BeaconChainError {
     ProposerHeadForkChoiceError(fork_choice::Error<proto_array::Error>),
     UnableToPublish,
     AvailabilityCheckError(AvailabilityCheckError),
+    LightClientError(LightClientError),
+    UnsupportedFork,
 }
 
 easy_from_to!(SlotProcessingError, BeaconChainError);

beacon_node/beacon_chain/src/events.rs

@@ -17,6 +17,8 @@ pub struct ServerSentEventHandler<T: EthSpec> {
     contribution_tx: Sender<EventKind<T>>,
     payload_attributes_tx: Sender<EventKind<T>>,
     late_head: Sender<EventKind<T>>,
+    light_client_finality_update_tx: Sender<EventKind<T>>,
+    light_client_optimistic_update_tx: Sender<EventKind<T>>,
     block_reward_tx: Sender<EventKind<T>>,
     log: Logger,
 }
@@ -40,6 +42,8 @@ impl<T: EthSpec> ServerSentEventHandler<T> {
         let (contribution_tx, _) = broadcast::channel(capacity);
         let (payload_attributes_tx, _) = broadcast::channel(capacity);
         let (late_head, _) = broadcast::channel(capacity);
+        let (light_client_finality_update_tx, _) = broadcast::channel(capacity);
+        let (light_client_optimistic_update_tx, _) = broadcast::channel(capacity);
         let (block_reward_tx, _) = broadcast::channel(capacity);
 
         Self {
@@ -53,6 +57,8 @@ impl<T: EthSpec> ServerSentEventHandler<T> {
             contribution_tx,
             payload_attributes_tx,
             late_head,
+            light_client_finality_update_tx,
+            light_client_optimistic_update_tx,
             block_reward_tx,
             log,
         }
@@ -108,6 +114,14 @@ impl<T: EthSpec> ServerSentEventHandler<T> {
                 .late_head
                 .send(kind)
                 .map(|count| log_count("late head", count)),
+            EventKind::LightClientFinalityUpdate(_) => self
+                .light_client_finality_update_tx
+                .send(kind)
+                .map(|count| log_count("light client finality update", count)),
+            EventKind::LightClientOptimisticUpdate(_) => self
+                .light_client_optimistic_update_tx
+                .send(kind)
+                .map(|count| log_count("light client optimistic update", count)),
             EventKind::BlockReward(_) => self
                 .block_reward_tx
                 .send(kind)
@@ -158,6 +172,14 @@ impl<T: EthSpec> ServerSentEventHandler<T> {
         self.late_head.subscribe()
     }
 
+    pub fn subscribe_light_client_finality_update(&self) -> Receiver<EventKind<T>> {
+        self.light_client_finality_update_tx.subscribe()
+    }
+
+    pub fn subscribe_light_client_optimistic_update(&self) -> Receiver<EventKind<T>> {
+        self.light_client_optimistic_update_tx.subscribe()
+    }
+
     pub fn subscribe_block_reward(&self) -> Receiver<EventKind<T>> {
         self.block_reward_tx.subscribe()
     }

beacon_node/beacon_chain/src/light_client_finality_update_verification.rs

@@ -67,7 +67,7 @@ impl<T: BeaconChainTypes> VerifiedLightClientFinalityUpdate<T> {
         chain: &BeaconChain<T>,
         seen_timestamp: Duration,
     ) -> Result<Self, Error> {
-        let gossiped_finality_slot = light_client_finality_update.finalized_header.slot;
+        let gossiped_finality_slot = light_client_finality_update.finalized_header.beacon.slot;
         let one_third_slot_duration = Duration::new(chain.spec.seconds_per_slot / 3, 0);
         let signature_slot = light_client_finality_update.signature_slot;
         let start_time = chain.slot_clock.start_of(signature_slot);
@@ -88,7 +88,7 @@ impl<T: BeaconChainTypes> VerifiedLightClientFinalityUpdate<T> {
             .get_blinded_block(&finalized_block_root)?
             .ok_or(Error::FailedConstructingUpdate)?;
         let latest_seen_finality_update_slot = match latest_seen_finality_update.as_ref() {
-            Some(update) => update.finalized_header.slot,
+            Some(update) => update.finalized_header.beacon.slot,
             None => Slot::new(0),
         };
 

beacon_node/beacon_chain/src/light_client_optimistic_update_verification.rs

@@ -71,7 +71,7 @@ impl<T: BeaconChainTypes> VerifiedLightClientOptimisticUpdate<T> {
         chain: &BeaconChain<T>,
         seen_timestamp: Duration,
     ) -> Result<Self, Error> {
-        let gossiped_optimistic_slot = light_client_optimistic_update.attested_header.slot;
+        let gossiped_optimistic_slot = light_client_optimistic_update.attested_header.beacon.slot;
         let one_third_slot_duration = Duration::new(chain.spec.seconds_per_slot / 3, 0);
         let signature_slot = light_client_optimistic_update.signature_slot;
         let start_time = chain.slot_clock.start_of(signature_slot);
@@ -88,7 +88,7 @@ impl<T: BeaconChainTypes> VerifiedLightClientOptimisticUpdate<T> {
             .get_state(&attested_block.state_root(), Some(attested_block.slot()))?
             .ok_or(Error::FailedConstructingUpdate)?;
         let latest_seen_optimistic_update_slot = match latest_seen_optimistic_update.as_ref() {
-            Some(update) => update.attested_header.slot,
+            Some(update) => update.attested_header.beacon.slot,
             None => Slot::new(0),
         };
 
@@ -114,6 +114,7 @@ impl<T: BeaconChainTypes> VerifiedLightClientOptimisticUpdate<T> {
         // otherwise queue
         let canonical_root = light_client_optimistic_update
             .attested_header
+            .beacon
             .canonical_root();
 
         if canonical_root != head_block.message().parent_root() {