add LightClientStore and keep it in sync

The `LightClientStore` represents client data when syncing using the
light client protocol. So far, Nimbus supported serving light client
data to other nodes but did not incorporate client functionality.
A new startup option is introduced, `light-client-trusted-block-root`,
to configure a block root from which light client sync can be started.
The `LightClientStore` is updated with new data from the network but is
not yet used for other purposes. Log messages are produced to reflect
applied updates ("Light client object processed").

beacon_chain/beacon_node.nim

@@ -15,14 +15,15 @@ import
 
   # Local modules
   "."/[beacon_clock, beacon_chain_db, conf],
-  ./gossip_processing/[eth2_processor, block_processor, consensus_manager],
+  ./gossip_processing/[
+    eth2_processor, block_processor, consensus_manager, light_client_processor],
   ./networking/eth2_network,
   ./eth1/eth1_monitor,
   ./consensus_object_pools/[
     blockchain_dag, block_quarantine, exit_pool, attestation_pool,
     sync_committee_msg_pool],
   ./spec/datatypes/base,
-  ./sync/[sync_manager, request_manager],
+  ./sync/[light_client_manager, sync_manager, request_manager],
   ./validators/[action_tracker, validator_monitor, validator_pool],
   ./rpc/state_ttl_cache
 
@@ -38,6 +39,12 @@ type
 
   GossipState* = set[BeaconStateFork]
 
+  LightClient* = object
+    trustedBlockRoot*: Option[Eth2Digest]
+    store*: ref Option[LightClientStore]
+    processor*: ref LightClientProcessor
+    manager*: LightClientManager
+
   BeaconNode* = ref object
     nickname*: string
     graffitiBytes*: GraffitiBytes
@@ -46,6 +53,7 @@ type
     db*: BeaconChainDB
     config*: BeaconNodeConf
     attachedValidators*: ref ValidatorPool
+    lightClient*: LightClient
     dag*: ChainDAGRef
     quarantine*: ref Quarantine
     attestationPool*: ref AttestationPool
@@ -87,3 +95,6 @@ template findIt*(s: openArray, predicate: untyped): int =
 
 proc currentSlot*(node: BeaconNode): Slot =
   node.beaconClock.now.slotOrZero
+
+import beacon_node_light_client
+export beacon_node_light_client

beacon_chain/beacon_node_light_client.nim

@@ -0,0 +1,87 @@
+# beacon_chain
+# Copyright (c) 2022 Status Research & Development GmbH
+# Licensed and distributed under either of
+#   * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
+#   * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
+# at your option. This file may not be copied, modified, or distributed except according to those terms.
+
+{.push raises: [Defect].}
+
+# This implements the pre-release proposal of the libp2p based light client sync
+# protocol. See https://github.com/ethereum/consensus-specs/pull/2802
+
+import
+  "."/beacon_node,
+  ./gossip_processing/light_client_processor,
+  ./spec/datatypes/altair,
+  ./sync/light_client_manager
+
+logScope: topics = "beacnde"
+
+proc initLightClient*(
+    node: BeaconNode,
+    cfg: RuntimeConfig,
+    rng: ref BrHmacDrbgContext,
+    genesis_validators_root: Eth2Digest,
+    getBeaconTime: GetBeaconTimeFn) =
+  template config(): auto = node.config
+
+  let store = (ref Option[LightClientStore])()
+
+  func getTrustedBlockRoot(): Option[Eth2Digest] =
+    node.lightClient.trustedBlockRoot
+
+  proc getLocalWallPeriod(): SyncCommitteePeriod =
+    node.beaconClock.now.slotOrZero.sync_committee_period
+
+  func getFinalizedPeriod(): SyncCommitteePeriod =
+    if store[].isSome:
+      store[].get.finalized_header.slot.sync_committee_period
+    else:
+      GENESIS_SLOT.sync_committee_period
+
+  func isLightClientStoreInitialized(): bool =
+    store[].isSome
+
+  func isNextSyncCommitteeKnown(): bool =
+    if store[].isSome:
+      not store[].get.next_sync_committee.isZeroMemory
+    else:
+      false
+
+  let lightClientProcessor = LightClientProcessor.new(
+    config.dumpEnabled, config.dumpDirInvalid, config.dumpDirIncoming,
+    cfg, genesis_validators_root, store, getBeaconTime, getTrustedBlockRoot)
+
+  proc lightClientVerifier(obj: SomeLightClientObject):
+      Future[Result[void, BlockError]] =
+    let resfut = newFuture[Result[void, BlockError]]("lightClientVerifier")
+    lightClientProcessor[].addObject(MsgSource.gossip, obj, resfut)
+    resfut
+  let
+    bootstrapVerifier = proc(obj: altair.LightClientBootstrap):
+        Future[Result[void, BlockError]] =
+      lightClientVerifier(obj)
+    updateVerifier = proc(obj: altair.LightClientUpdate):
+        Future[Result[void, BlockError]] =
+      lightClientVerifier(obj)
+    optimisticUpdateVerifier = proc(obj: OptimisticLightClientUpdate):
+        Future[Result[void, BlockError]] =
+      lightClientVerifier(obj)
+
+  node.lightClient.trustedBlockRoot = config.lightClientTrustedBlockRoot
+  node.lightClient.store = store
+  node.lightClient.processor = lightClientProcessor
+  node.lightClient.manager = LightClientManager.init(
+    node.network, rng, getTrustedBlockRoot,
+    bootstrapVerifier, updateVerifier, optimisticUpdateVerifier,
+    getLocalWallPeriod, getFinalizedPeriod,
+    isLightClientStoreInitialized, isNextSyncCommitteeKnown)
+
+proc startLightClient*(node: BeaconNode) =
+  if node.lightClient.trustedBlockRoot.isNone:
+    return
+
+  notice "Starting light client",
+    trusted_block_root = node.lightClient.trustedBlockRoot.get
+  node.lightClient.manager.start()

beacon_chain/conf.nim

@@ -273,6 +273,11 @@ type
         desc: "Weak subjectivity checkpoint in the format block_root:epoch_number"
         name: "weak-subjectivity-checkpoint" }: Option[Checkpoint]
 
+      lightClientTrustedBlockRoot* {.
+        hidden
+        desc: "BETA: Recent trusted finalized block root for accelerating sync using the light client protocol."
+        name: "light-client-trusted-block-root" }: Option[Eth2Digest]
+
       finalizedCheckpointState* {.
         desc: "SSZ file specifying a recent finalized state"
         name: "finalized-checkpoint-state" }: Option[InputFile]
@@ -909,6 +914,13 @@ proc createDumpDirs*(config: BeaconNodeConf) =
       warn "Could not create dump directory",
         path = config.dumpDirOutgoing, err = ioErrorMsg(res.error)
 
+func parseCmdArg*(T: type Eth2Digest, input: string): T
+                 {.raises: [ValueError, Defect].} =
+  Eth2Digest.fromHex(input)
+
+func completeCmdArg*(T: type Eth2Digest, input: string): seq[string] =
+  return @[]
+
 func parseCmdArg*(T: type GraffitiBytes, input: string): T
                  {.raises: [ValueError, Defect].} =
   GraffitiBytes.init(input)

beacon_chain/gossip_processing/light_client_processor.nim

@@ -26,6 +26,8 @@ declareHistogram light_client_store_object_duration_seconds,
   "storeObject() duration", buckets = [0.25, 0.5, 1, 2, 4, 8, Inf]
 
 type
+  GetTrustedBlockRootCallback* =
+    proc(): Option[Eth2Digest] {.gcsafe, raises: [Defect].}
   DidInitializeStoreCallback* =
     proc() {.gcsafe, raises: [Defect].}
 
@@ -57,12 +59,12 @@ type
     # Consumer
     # ----------------------------------------------------------------
     store: ref Option[LightClientStore]
-    getBeaconTime*: GetBeaconTimeFn
+    getBeaconTime: GetBeaconTimeFn
+    getTrustedBlockRoot: GetTrustedBlockRootCallback
     didInitializeStoreCallback: DidInitializeStoreCallback
 
     cfg: RuntimeConfig
     genesis_validators_root: Eth2Digest
-    trustedBlockRoot: Eth2Digest
 
     lastProgressTick: BeaconTime # Moment when last update made progress
     lastDuplicateTick: BeaconTime # Moment when last duplicate update received
@@ -83,9 +85,10 @@ proc new*(
     dumpEnabled: bool,
     dumpDirInvalid, dumpDirIncoming: string,
     cfg: RuntimeConfig,
-    genesis_validators_root, trustedBlockRoot: Eth2Digest,
+    genesis_validators_root: Eth2Digest,
     store: ref Option[LightClientStore],
     getBeaconTime: GetBeaconTimeFn,
+    getTrustedBlockRoot: GetTrustedBlockRootCallback,
     didInitializeStoreCallback: DidInitializeStoreCallback = nil
 ): ref LightClientProcessor =
   (ref LightClientProcessor)(
@@ -94,12 +97,18 @@ proc new*(
     dumpDirIncoming: dumpDirIncoming,
     store: store,
     getBeaconTime: getBeaconTime,
+    getTrustedBlockRoot: getTrustedBlockRoot,
     didInitializeStoreCallback: didInitializeStoreCallback,
     cfg: cfg,
-    genesis_validators_root: genesis_validators_root,
-    trustedBlockRoot: trustedBlockRoot
+    genesis_validators_root: genesis_validators_root
   )
 
+func resetStore*(self: var LightClientProcessor) =
+  self.store[].reset()
+  self.lastProgressTick.reset()
+  self.lastDuplicateTick.reset()
+  self.numDuplicatesSinceProgress.reset()
+
 # Storage
 # ------------------------------------------------------------------------------
 
@@ -160,21 +169,25 @@ proc storeObject*(
         if store[].isSome:
           err(BlockError.Duplicate)
         else:
-          let initRes = initialize_light_client_store(
-            self.trustedBlockRoot, obj)
-          if initRes.isErr:
-            err(initRes.error)
+          let trustedBlockRoot = self.getTrustedBlockRoot()
+          if trustedBlockRoot.isNone:
+            err(BlockError.MissingParent)
           else:
-            store[] = some(initRes.get)
-            ok()
+            let initRes =
+              initialize_light_client_store(trustedBlockRoot.get, obj)
+            if initRes.isErr:
+              err(initRes.error)
+            else:
+              store[] = some(initRes.get)
+              ok()
       elif obj is altair.LightClientUpdate:
         if store[].isNone:
           err(BlockError.MissingParent)
         else:
           store[].get.process_light_client_update(
             obj, wallSlot, self.cfg, self.genesis_validators_root,
             allowForceUpdate = false)
-      elif obj is altair.OptimisticLightClientUpdate:
+      elif obj is OptimisticLightClientUpdate:
         if store[].isNone:
           err(BlockError.MissingParent)
         else:

beacon_chain/nimbus_beacon_node.nim

@@ -656,7 +656,7 @@ proc init*(T: type BeaconNode,
       else:
         nil
 
-  var node = BeaconNode(
+  let node = BeaconNode(
     nickname: nickname,
     graffitiBytes: if config.graffiti.isSome: config.graffiti.get
                    else: defaultGraffitiBytes(),
@@ -677,10 +677,8 @@ proc init*(T: type BeaconNode,
     validatorMonitor: validatorMonitor,
     stateTtlCache: stateTtlCache
   )
-
-  node.initFullNode(
-    rng, dag, taskpool, getBeaconTime)
-
+  node.initLightClient(cfg, rng, dag.genesis_validators_root, getBeaconTime)
+  node.initFullNode(rng, dag, taskpool, getBeaconTime)
   node
 
 func verifyFinalization(node: BeaconNode, slot: Slot) =
@@ -1458,6 +1456,7 @@ proc run(node: BeaconNode) {.raises: [Defect, CatchableError].} =
     wallTime = node.beaconClock.now()
     wallSlot = wallTime.slotOrZero()
 
+  node.startLightClient()
   node.requestManager.start()
   node.syncManager.start()