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Bump is_better_update to match latest spec #6914

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Merged
tersec merged 1 commit into from
Feb 11, 2025
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Bump is_better_update to match latest spec #6914

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24 changes: 14 additions & 10 deletions beacon_chain/spec/helpers.nim
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Original file line number Diff line number Diff line change
Expand Up @@ -279,7 +279,7 @@ func get_safety_threshold*(store: ForkyLightClientStore): uint64 =
store.current_max_active_participants
) div 2

# https://github.com/ethereum/consensus-specs/blob/v1.4.0-beta.5/specs/altair/light-client/sync-protocol.md#is_better_update
# https://github.com/ethereum/consensus-specs/blob/v1.5.0-beta.3/specs/altair/light-client/sync-protocol.md#is_better_update
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@tersec tersec Feb 11, 2025

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doesn't seem to exist?

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@tersec tersec Feb 11, 2025

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or is this coming in next spec release?

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@etan-status etan-status Feb 11, 2025

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the linked PR is not part of b.2, so anticipating b.3

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@etan-status etan-status Feb 11, 2025

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Like, it was merged into dev upstream from which they branch releases.

type LightClientUpdateMetadata* = object
attested_slot*, finalized_slot*, signature_slot*: Slot
has_sync_committee*, has_finality*: bool
Expand Down Expand Up @@ -326,10 +326,10 @@ func is_better_data*(new_meta, old_meta: LightClientUpdateMetadata): bool =
old_has_supermajority =
hasSupermajoritySyncParticipation(old_meta.num_active_participants)
if new_has_supermajority != old_has_supermajority:
return new_has_supermajority > old_has_supermajority
if not new_has_supermajority:
if new_meta.num_active_participants != old_meta.num_active_participants:
return new_meta.num_active_participants > old_meta.num_active_participants
return new_has_supermajority
if not new_has_supermajority and
new_meta.num_active_participants != old_meta.num_active_participants:
return new_meta.num_active_participants > old_meta.num_active_participants

# Compare presence of relevant sync committee
let
Expand All @@ -340,11 +340,11 @@ func is_better_data*(new_meta, old_meta: LightClientUpdateMetadata): bool =
old_meta.attested_slot.sync_committee_period ==
old_meta.signature_slot.sync_committee_period
if new_has_relevant_sync_committee != old_has_relevant_sync_committee:
return new_has_relevant_sync_committee > old_has_relevant_sync_committee
return new_has_relevant_sync_committee

# Compare indication of any finality
if new_meta.has_finality != old_meta.has_finality:
return new_meta.has_finality > old_meta.has_finality
return new_meta.has_finality

# Compare sync committee finality
if new_meta.has_finality:
Expand All @@ -356,14 +356,18 @@ func is_better_data*(new_meta, old_meta: LightClientUpdateMetadata): bool =
old_meta.finalized_slot.sync_committee_period ==
old_meta.attested_slot.sync_committee_period
if new_has_sync_committee_finality != old_has_sync_committee_finality:
return new_has_sync_committee_finality > old_has_sync_committee_finality
return new_has_sync_committee_finality

# Tiebreaker 1: Sync committee participation beyond supermajority
if new_meta.num_active_participants != old_meta.num_active_participants:
return new_meta.num_active_participants > old_meta.num_active_participants

# Tiebreaker 2: Prefer older data (fewer changes to best data)
new_meta.attested_slot < old_meta.attested_slot
# Tiebreaker 2: Prefer older data (fewer changes to best)
if new_meta.attested_slot != old_meta.attested_slot:
return new_meta.attested_slot < old_meta.attested_slot

# Tiebreaker 3: Prefer updates with earlier signature slots
new_meta.signature_slot < old_meta.signature_slot

template is_better_update*[
A, B: SomeForkyLightClientUpdate | ForkedLightClientUpdate](
Expand Down