461 lines
17 KiB
Nim
461 lines
17 KiB
Nim
# beacon_chain
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# Copyright (c) 2022 Status Research & Development GmbH
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# Licensed and distributed under either of
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# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
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# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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when (NimMajor, NimMinor) < (1, 4):
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{.push raises: [Defect].}
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else:
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{.push raises: [].}
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import
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stew/objects,
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chronos, metrics,
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../spec/datatypes/altair,
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../spec/light_client_sync,
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../consensus_object_pools/block_pools_types,
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".."/[beacon_clock, sszdump],
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"."/[eth2_processor, gossip_validation]
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export sszdump, eth2_processor, gossip_validation
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logScope: topics = "gossip_lc"
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# Light Client Processor
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# ------------------------------------------------------------------------------
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# The light client processor handles received light client objects
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declareHistogram light_client_store_object_duration_seconds,
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"storeObject() duration", buckets = [0.25, 0.5, 1, 2, 4, 8, Inf]
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type
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GetTrustedBlockRootCallback* =
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proc(): Option[Eth2Digest] {.gcsafe, raises: [Defect].}
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VoidCallback* =
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proc() {.gcsafe, raises: [Defect].}
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LightClientFinalizationMode* {.pure.} = enum
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Strict
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## Only finalize light client data that:
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## - has been signed by a supermajority (2/3) of the sync committee
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## - has a valid finality proof
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##
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## Optimizes for security, but may become stuck if there is any of:
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## - non-finality for an entire sync committee period
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## - low sync committee participation for an entire sync committee period
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## Such periods need to be covered by an out-of-band syncing mechanism.
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##
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## Note that a compromised supermajority of the sync committee is able to
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## sign arbitrary light client data, even after being slashed. The light
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## client cannot validate the slashing status of sync committee members.
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## Likewise, voluntarily exited validators may sign bad light client data
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## for the sync committee periods in which they used to be selected.
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Optimistic
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## Attempt to finalize light client data not satisfying strict conditions
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## if there is no progress for an extended period of time and if there are
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## repeated messages indicating that it is the best available data on the
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## network for the affected time period.
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##
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## Optimizes for availability of recent data, but may end up on incorrect
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## forks if run in a hostile network environment (no honest peers), or if
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## the low sync committee participation is being exploited by bad actors.
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LightClientProcessor* = object
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## This manages the processing of received light client objects
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##
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## from:
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## - Gossip:
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## - `LightClientFinalityUpdate`
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## - `LightClientOptimisticUpdate`
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## - `LightClientManager`:
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## - `GetLightClientBootstrap`
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## - `LightClientUpdatesByRange`
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## - `GetLightClientFinalityUpdate`
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## - `GetLightClientOptimisticUpdate`
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##
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## are then verified and added to:
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## - `LightClientStore`
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# Config
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# ----------------------------------------------------------------
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dumpEnabled: bool
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dumpDirInvalid: string
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dumpDirIncoming: string
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# Consumer
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# ----------------------------------------------------------------
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store: ref Option[LightClientStore]
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getBeaconTime: GetBeaconTimeFn
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getTrustedBlockRoot: GetTrustedBlockRootCallback
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onStoreInitialized, onFinalizedHeader, onOptimisticHeader: VoidCallback
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cfg: RuntimeConfig
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genesis_validators_root: Eth2Digest
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case finalizationMode: LightClientFinalizationMode
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of LightClientFinalizationMode.Strict:
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discard
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of LightClientFinalizationMode.Optimistic:
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lastProgressTick: BeaconTime # Moment when last update made progress
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lastDuplicateTick: BeaconTime # Moment when last duplicate update received
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numDuplicatesSinceProgress: int # Number of duplicates since last progress
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latestFinalityUpdate: altair.LightClientOptimisticUpdate
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const
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# These constants have been chosen empirically and are not backed by spec
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duplicateRateLimit = chronos.seconds(5) # Rate limit for counting duplicates
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duplicateCountDelay = chronos.minutes(15) # Delay to start counting duplicates
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minForceUpdateDelay = chronos.minutes(30) # Minimum delay until forced-update
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minForceUpdateDuplicates = 100 # Minimum duplicates until forced-update
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# Initialization
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# ------------------------------------------------------------------------------
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proc new*(
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T: type LightClientProcessor,
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dumpEnabled: bool,
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dumpDirInvalid, dumpDirIncoming: string,
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cfg: RuntimeConfig,
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genesis_validators_root: Eth2Digest,
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finalizationMode: LightClientFinalizationMode,
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store: ref Option[LightClientStore],
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getBeaconTime: GetBeaconTimeFn,
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getTrustedBlockRoot: GetTrustedBlockRootCallback,
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onStoreInitialized: VoidCallback = nil,
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onFinalizedHeader: VoidCallback = nil,
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onOptimisticHeader: VoidCallback = nil
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): ref LightClientProcessor =
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(ref LightClientProcessor)(
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dumpEnabled: dumpEnabled,
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dumpDirInvalid: dumpDirInvalid,
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dumpDirIncoming: dumpDirIncoming,
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store: store,
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getBeaconTime: getBeaconTime,
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getTrustedBlockRoot: getTrustedBlockRoot,
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onStoreInitialized: onStoreInitialized,
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onFinalizedHeader: onFinalizedHeader,
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onOptimisticHeader: onOptimisticHeader,
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cfg: cfg,
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genesis_validators_root: genesis_validators_root,
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finalizationMode: finalizationMode)
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# Storage
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# ------------------------------------------------------------------------------
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proc dumpInvalidObject(
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self: LightClientProcessor,
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obj: SomeLightClientObject) =
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if self.dumpEnabled:
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dump(self.dumpDirInvalid, obj)
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proc dumpObject[T](
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self: LightClientProcessor,
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obj: SomeLightClientObject,
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res: Result[T, BlockError]) =
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if self.dumpEnabled and res.isErr:
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case res.error
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of BlockError.Invalid:
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self.dumpInvalidObject(obj)
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of BlockError.MissingParent:
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dump(self.dumpDirIncoming, obj)
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else:
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discard
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proc tryForceUpdate(
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self: var LightClientProcessor,
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wallTime: BeaconTime) =
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## Try to force-update to the next sync committee period.
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let
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wallSlot = wallTime.slotOrZero()
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store = self.store
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if store[].isSome:
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doAssert self.finalizationMode == LightClientFinalizationMode.Optimistic
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case store[].get.process_light_client_store_force_update(wallSlot)
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of NoUpdate:
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discard
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of DidUpdateWithoutSupermajority:
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warn "Light client force-updated without supermajority",
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finalizedSlot = store[].get.finalized_header.slot,
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optimisticSlot = store[].get.optimistic_header.slot
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of DidUpdateWithoutFinality:
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warn "Light client force-updated without finality proof",
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finalizedSlot = store[].get.finalized_header.slot,
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optimisticSlot = store[].get.optimistic_header.slot
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proc processObject(
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self: var LightClientProcessor,
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obj: SomeLightClientObject,
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wallTime: BeaconTime): Result[void, BlockError] =
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let
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wallSlot = wallTime.slotOrZero()
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store = self.store
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res =
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when obj is altair.LightClientBootstrap:
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if store[].isSome:
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err(BlockError.Duplicate)
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else:
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let trustedBlockRoot = self.getTrustedBlockRoot()
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if trustedBlockRoot.isNone:
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err(BlockError.MissingParent)
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else:
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let initRes =
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initialize_light_client_store(trustedBlockRoot.get, obj)
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if initRes.isErr:
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err(initRes.error)
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else:
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store[] = some(initRes.get)
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ok()
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elif obj is SomeLightClientUpdate:
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if store[].isNone:
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err(BlockError.MissingParent)
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else:
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store[].get.process_light_client_update(
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obj, wallSlot, self.cfg, self.genesis_validators_root)
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self.dumpObject(obj, res)
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if res.isErr:
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when obj is altair.LightClientUpdate:
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if self.finalizationMode == LightClientFinalizationMode.Optimistic and
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store[].isSome and store[].get.best_valid_update.isSome:
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# `best_valid_update` gets set when no supermajority / finality proof
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# is available. In that case, we will wait for a better update.
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# If none is made available within reasonable time, the light client
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# is force-updated using the best known data to ensure sync progress.
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case res.error
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of BlockError.Duplicate:
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if wallTime >= self.lastDuplicateTick + duplicateRateLimit:
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if self.numDuplicatesSinceProgress < minForceUpdateDuplicates:
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if obj.matches(store[].get.best_valid_update.get):
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self.lastDuplicateTick = wallTime
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inc self.numDuplicatesSinceProgress
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if self.numDuplicatesSinceProgress >= minForceUpdateDuplicates and
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wallTime >= self.lastProgressTick + minForceUpdateDelay:
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self.tryForceUpdate(wallTime)
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self.lastProgressTick = wallTime
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self.lastDuplicateTick = wallTime + duplicateCountDelay
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self.numDuplicatesSinceProgress = 0
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else: discard
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return res
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when obj is altair.LightClientBootstrap | altair.LightClientUpdate:
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if self.finalizationMode == LightClientFinalizationMode.Optimistic:
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self.lastProgressTick = wallTime
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self.lastDuplicateTick = wallTime + duplicateCountDelay
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self.numDuplicatesSinceProgress = 0
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res
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template withReportedProgress(expectFinalityUpdate: bool, body: untyped): bool =
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block:
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let
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previousWasInitialized = store[].isSome
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previousFinalized =
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if store[].isSome:
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store[].get.finalized_header
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else:
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BeaconBlockHeader()
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previousOptimistic =
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if store[].isSome:
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store[].get.optimistic_header
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else:
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BeaconBlockHeader()
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body
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var didProgress = false
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if store[].isSome != previousWasInitialized:
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didProgress = true
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if self.onStoreInitialized != nil:
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self.onStoreInitialized()
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self.onStoreInitialized = nil
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if store[].get.optimistic_header != previousOptimistic:
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when not expectFinalityUpdate:
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didProgress = true
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if self.onOptimisticHeader != nil:
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self.onOptimisticHeader()
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if store[].get.finalized_header != previousFinalized:
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didProgress = true
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if self.onFinalizedHeader != nil:
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self.onFinalizedHeader()
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didProgress
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template withReportedProgress(body: untyped): bool =
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withReportedProgress(false, body)
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proc storeObject*(
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self: var LightClientProcessor,
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src: MsgSource, wallTime: BeaconTime,
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obj: SomeLightClientObject): Result[bool, BlockError] =
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## storeObject is the main entry point for unvalidated light client objects -
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## all untrusted objects pass through here. When storing an object, we will
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## update the `LightClientStore` accordingly
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let
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startTick = Moment.now()
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store = self.store
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didProgress =
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withReportedProgress(obj is SomeLightClientUpdateWithFinality):
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? self.processObject(obj, wallTime)
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let
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storeObjectTick = Moment.now()
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storeObjectDur = storeObjectTick - startTick
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light_client_store_object_duration_seconds.observe(
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storeObjectDur.toFloatSeconds())
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let objSlot =
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when obj is altair.LightClientBootstrap:
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obj.header.slot
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elif obj is SomeLightClientUpdateWithFinality:
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obj.finalized_header.slot
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else:
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obj.attested_header.slot
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debug "LC object processed",
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finalizedSlot = store[].get.finalized_header.slot,
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optimisticSlot = store[].get.optimistic_header.slot,
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kind = typeof(obj).name,
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objectSlot = objSlot,
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storeObjectDur
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ok didProgress
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proc resetToFinalizedHeader*(
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self: var LightClientProcessor,
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header: BeaconBlockHeader,
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current_sync_committee: SyncCommittee) =
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let store = self.store
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discard withReportedProgress:
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store[] = some LightClientStore(
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finalized_header: header,
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current_sync_committee: current_sync_committee,
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optimistic_header: header)
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debug "LC reset to finalized header",
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finalizedSlot = store[].get.finalized_header.slot,
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optimisticSlot = store[].get.optimistic_header.slot
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# Enqueue
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# ------------------------------------------------------------------------------
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proc addObject*(
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self: var LightClientProcessor,
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src: MsgSource,
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obj: SomeLightClientObject,
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resfut: Future[Result[void, BlockError]] = nil) =
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## Enqueue a Gossip-validated light client object for verification
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# Backpressure:
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# Only one object is validated at any time -
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# Light client objects are always "fast" to process
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# Producers:
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# - Gossip:
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# - `LightClientFinalityUpdate`
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# - `LightClientOptimisticUpdate`
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# - `LightClientManager`:
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# - `GetLightClientBootstrap`
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# - `LightClientUpdatesByRange`
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# - `GetLightClientFinalityUpdate`
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# - `GetLightClientOptimisticUpdate`
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let
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wallTime = self.getBeaconTime()
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(afterGenesis, wallSlot) = wallTime.toSlot()
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if not afterGenesis:
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error "Processing LC object before genesis, clock turned back?"
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quit 1
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let res = self.storeObject(src, wallTime, obj)
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if resfut != nil:
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if res.isOk:
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resfut.complete(Result[void, BlockError].ok())
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else:
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resfut.complete(Result[void, BlockError].err(res.error))
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# Message validators
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# ------------------------------------------------------------------------------
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func toValidationError(
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self: var LightClientProcessor,
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r: Result[bool, BlockError],
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wallTime: BeaconTime,
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obj: SomeLightClientObject): Result[void, ValidationError] =
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if r.isOk:
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let didProgress = r.get
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if didProgress:
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let
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signature_slot = obj.signature_slot
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currentTime = wallTime + MAXIMUM_GOSSIP_CLOCK_DISPARITY
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forwardTime = signature_slot.light_client_finality_update_time
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if currentTime < forwardTime:
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# [IGNORE] The `finality_update` is received after the block
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# at `signature_slot` was given enough time to propagate through
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# the network.
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# [IGNORE] The `optimistic_update` is received after the block
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# at `signature_slot` was given enough time to propagate through
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# the network.
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return errIgnore(typeof(obj).name & ": received too early")
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ok()
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else:
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when obj is altair.LightClientOptimisticUpdate:
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# [IGNORE] The `optimistic_update` either matches corresponding fields
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# of the most recently forwarded `LightClientFinalityUpdate` (if any),
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# or it advances the `optimistic_header` of the local `LightClientStore`
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if obj == self.latestFinalityUpdate:
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return ok()
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# [IGNORE] The `finality_update` advances the `finalized_header` of the
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# local `LightClientStore`.
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errIgnore(typeof(obj).name & ": no significant progress")
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else:
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case r.error
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of BlockError.Invalid:
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# [REJECT] The `finality_update` is valid.
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# [REJECT] The `optimistic_update` is valid.
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errReject($r.error)
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of BlockError.MissingParent, BlockError.UnviableFork, BlockError.Duplicate:
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# [IGNORE] No other `finality_update` with a lower or equal
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# `finalized_header.slot` was already forwarded on the network.
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# [IGNORE] No other `optimistic_update` with a lower or equal
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# `attested_header.slot` was already forwarded on the network.
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errIgnore($r.error)
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# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/altair/light-client/sync-protocol.md#process_light_client_finality_update
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proc processLightClientFinalityUpdate*(
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self: var LightClientProcessor, src: MsgSource,
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finality_update: altair.LightClientFinalityUpdate
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): Result[void, ValidationError] =
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let
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wallTime = self.getBeaconTime()
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r = self.storeObject(src, wallTime, finality_update)
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v = self.toValidationError(r, wallTime, finality_update)
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if v.isOk:
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self.latestFinalityUpdate = finality_update.toOptimistic
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v
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# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/altair/light-client/sync-protocol.md#process_light_client_finality_update
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proc processLightClientOptimisticUpdate*(
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self: var LightClientProcessor, src: MsgSource,
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optimistic_update: altair.LightClientOptimisticUpdate
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): Result[void, ValidationError] =
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let
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wallTime = self.getBeaconTime()
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r = self.storeObject(src, wallTime, optimistic_update)
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v = self.toValidationError(r, wallTime, optimistic_update)
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if v.isOk:
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let latestFinalitySlot = self.latestFinalityUpdate.attested_header.slot
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if optimistic_update.attested_header.slot >= latestFinalitySlot:
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self.latestFinalityUpdate.reset() # Only forward once
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v
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