use v1.1.7 test vectors

ConsensusSpecPreset-mainnet.md

@@ -739,7 +739,6 @@ OK: 1/1 Fail: 0/1 Skip: 0/1
 +   Testing    ForkData                                                                      OK
 +   Testing    HistoricalBatch                                                               OK
 +   Testing    IndexedAttestation                                                            OK
-+   Testing    LightClientSnapshot                                                           OK
 +   Testing    LightClientUpdate                                                             OK
 +   Testing    PendingAttestation                                                            OK
 +   Testing    ProposerSlashing                                                              OK
@@ -757,12 +756,12 @@ OK: 1/1 Fail: 0/1 Skip: 0/1
 +   Testing    Validator                                                                     OK
 +   Testing    VoluntaryExit                                                                 OK
 ```
-OK: 36/36 Fail: 0/36 Skip: 0/36
+OK: 35/35 Fail: 0/35 Skip: 0/35
 ## Ethereum Foundation - Altair - Unittests - Sync protocol [Preset: mainnet]
 ```diff
 + process_light_client_update_finality_updated                                               OK
-+ process_light_client_update_not_updated                                                    OK
 + process_light_client_update_timeout                                                        OK
++ test_process_light_client_update_not_timeout                                               OK
 ```
 OK: 3/3 Fail: 0/3 Skip: 0/3
 ## Ethereum Foundation - ForkChoice [Preset: mainnet]
@@ -902,7 +901,6 @@ OK: 1/1 Fail: 0/1 Skip: 0/1
 +   Testing    ForkData                                                                      OK
 +   Testing    HistoricalBatch                                                               OK
 +   Testing    IndexedAttestation                                                            OK
-+   Testing    LightClientSnapshot                                                           OK
 +   Testing    LightClientUpdate                                                             OK
 +   Testing    PendingAttestation                                                            OK
 +   Testing    PowBlock                                                                      OK
@@ -921,7 +919,7 @@ OK: 1/1 Fail: 0/1 Skip: 0/1
 +   Testing    Validator                                                                     OK
 +   Testing    VoluntaryExit                                                                 OK
 ```
-OK: 39/39 Fail: 0/39 Skip: 0/39
+OK: 38/38 Fail: 0/38 Skip: 0/38
 ## Ethereum Foundation - Phase 0 - Epoch Processing - Effective balance updates [Preset: mainnet]
 ```diff
 + Effective balance updates - effective_balance_hysteresis [Preset: mainnet]                 OK
@@ -1167,4 +1165,4 @@ OK: 44/44 Fail: 0/44 Skip: 0/44
 OK: 27/27 Fail: 0/27 Skip: 0/27
 
 ---TOTAL---
-OK: 991/993 Fail: 0/993 Skip: 2/993
+OK: 989/991 Fail: 0/991 Skip: 2/991

ConsensusSpecPreset-minimal.md

@@ -775,7 +775,6 @@ OK: 5/5 Fail: 0/5 Skip: 0/5
 +   Testing    ForkData                                                                      OK
 +   Testing    HistoricalBatch                                                               OK
 +   Testing    IndexedAttestation                                                            OK
-+   Testing    LightClientSnapshot                                                           OK
 +   Testing    LightClientUpdate                                                             OK
 +   Testing    PendingAttestation                                                            OK
 +   Testing    ProposerSlashing                                                              OK
@@ -793,12 +792,12 @@ OK: 5/5 Fail: 0/5 Skip: 0/5
 +   Testing    Validator                                                                     OK
 +   Testing    VoluntaryExit                                                                 OK
 ```
-OK: 36/36 Fail: 0/36 Skip: 0/36
+OK: 35/35 Fail: 0/35 Skip: 0/35
 ## Ethereum Foundation - Altair - Unittests - Sync protocol [Preset: minimal]
 ```diff
 + process_light_client_update_finality_updated                                               OK
-+ process_light_client_update_not_updated                                                    OK
 + process_light_client_update_timeout                                                        OK
++ test_process_light_client_update_not_timeout                                               OK
 ```
 OK: 3/3 Fail: 0/3 Skip: 0/3
 ## Ethereum Foundation - ForkChoice [Preset: minimal]
@@ -963,7 +962,6 @@ OK: 5/5 Fail: 0/5 Skip: 0/5
 +   Testing    ForkData                                                                      OK
 +   Testing    HistoricalBatch                                                               OK
 +   Testing    IndexedAttestation                                                            OK
-+   Testing    LightClientSnapshot                                                           OK
 +   Testing    LightClientUpdate                                                             OK
 +   Testing    PendingAttestation                                                            OK
 +   Testing    PowBlock                                                                      OK
@@ -982,7 +980,7 @@ OK: 5/5 Fail: 0/5 Skip: 0/5
 +   Testing    Validator                                                                     OK
 +   Testing    VoluntaryExit                                                                 OK
 ```
-OK: 39/39 Fail: 0/39 Skip: 0/39
+OK: 38/38 Fail: 0/38 Skip: 0/38
 ## Ethereum Foundation - Phase 0 - Epoch Processing - Effective balance updates [Preset: minimal]
 ```diff
 + Effective balance updates - effective_balance_hysteresis [Preset: minimal]                 OK
@@ -1239,4 +1237,4 @@ OK: 48/48 Fail: 0/48 Skip: 0/48
 OK: 30/30 Fail: 0/30 Skip: 0/30
 
 ---TOTAL---
-OK: 1037/1057 Fail: 0/1057 Skip: 20/1057
+OK: 1035/1055 Fail: 0/1055 Skip: 20/1055

beacon_chain/spec/datatypes/altair.nim

@@ -65,6 +65,10 @@ const
   INACTIVITY_SCORE_BIAS* = 4
   INACTIVITY_SCORE_RECOVERY_RATE* = 16
 
+  # https://github.com/ethereum/consensus-specs/blob/v1.1.7/specs/altair/sync-protocol.md#misc
+  # MIN_SYNC_COMMITTEE_PARTICIPANTS defined in presets
+  UPDATE_TIMEOUT* = SLOTS_PER_EPOCH * EPOCHS_PER_SYNC_COMMITTEE_PERIOD
+
   SYNC_SUBCOMMITTEE_SIZE* = SYNC_COMMITTEE_SIZE div SYNC_COMMITTEE_SUBNET_COUNT
 
 # "Note: The sum of the weights equal WEIGHT_DENOMINATOR."
@@ -146,41 +150,45 @@ type
 
   ### Modified/overloaded
 
-  # https://github.com/ethereum/consensus-specs/blob/v1.1.6/specs/altair/sync-protocol.md#lightclientsnapshot
-  LightClientSnapshot* = object
-    header*: BeaconBlockHeader ##\
-    ## Beacon block header
-
-    current_sync_committee*: SyncCommittee ##\
-    ## Sync committees corresponding to the header
-
-    next_sync_committee*: SyncCommittee
-
-  # https://github.com/ethereum/consensus-specs/blob/v1.1.6/specs/altair/sync-protocol.md#lightclientupdate
+  # https://github.com/ethereum/consensus-specs/blob/v1.1.7/specs/altair/sync-protocol.md#lightclientupdate
   LightClientUpdate* = object
-    header*: BeaconBlockHeader  ##\
-    ## Update beacon block header
+    attested_header*: BeaconBlockHeader ##\
+    ## The beacon block header that is attested to by the sync committee
 
-    # Next sync committee corresponding to the header
+    # Next sync committee corresponding to the active header
     next_sync_committee*: SyncCommittee
-    next_sync_committee_branch*: array[log2trunc(NEXT_SYNC_COMMITTEE_INDEX), Eth2Digest]
+    next_sync_committee_branch*:
+      array[log2trunc(NEXT_SYNC_COMMITTEE_INDEX), Eth2Digest]
 
-    # Finality proof for the update header
-    finality_header*: BeaconBlockHeader
+    # The finalized beacon block header attested to by Merkle branch
+    finalized_header*: BeaconBlockHeader
     finality_branch*: array[log2trunc(FINALIZED_ROOT_INDEX), Eth2Digest]
 
     # Sync committee aggregate signature
-    sync_committee_bits*: BitArray[SYNC_COMMITTEE_SIZE]
-    sync_committee_signature*: ValidatorSig
+    sync_committee_aggregate*: SyncAggregate
 
     fork_version*: Version ##\
     ## Fork version for the aggregate signature
 
-  # https://github.com/ethereum/consensus-specs/blob/v1.1.6/specs/altair/sync-protocol.md#lightclientstore
+  # https://github.com/ethereum/consensus-specs/blob/v1.1.7/specs/altair/sync-protocol.md#lightclientstore
   LightClientStore* = object
-    snapshot*: LightClientSnapshot
-    valid_updates*: HashSet[LightClientUpdate]
-      ## TODO: This will benefit from being an ordered set
+    finalized_header*: BeaconBlockHeader ##\
+    ## Beacon block header that is finalized
+
+    # Sync committees corresponding to the header
+    current_sync_committee*: SyncCommittee
+    next_sync_committee*: SyncCommittee
+
+    best_valid_update*: Option[LightClientUpdate] ##\
+    ## Best available header to switch finalized head to if we see nothing else
+
+    optimistic_header*: BeaconBlockHeader ##\
+    ## Most recent available reasonably-safe header
+
+    # Max number of active participants in a sync committee (used to calculate
+    # safety threshold)
+    previous_max_active_participants*: uint64
+    current_max_active_participants*: uint64
 
   # https://github.com/ethereum/consensus-specs/blob/v1.1.6/specs/altair/beacon-chain.md#beaconstate
   BeaconState* = object

beacon_chain/spec/datatypes/base.nim

@@ -57,7 +57,7 @@ export
 # Eventually, we could also differentiate between user/tainted data and
 # internal state that's gone through sanity checks already.
 
-const SPEC_VERSION* = "1.1.6"
+const SPEC_VERSION* = "1.1.7"
 ## Spec version we're aiming to be compatible with, right now
 
 const

beacon_chain/spec/light_client_sync.nim

@@ -4,112 +4,147 @@ import
   datatypes/altair,
   helpers
 
-# https://github.com/ethereum/consensus-specs/blob/v1.1.0/specs/altair/sync-protocol.md#validate_light_client_update
-proc validate_light_client_update*(snapshot: LightClientSnapshot,
+# https://github.com/ethereum/consensus-specs/blob/v1.1.7/specs/altair/sync-protocol.md#get_active_header
+func get_active_header(update: LightClientUpdate): BeaconBlockHeader =
+  # The "active header" is the header that the update is trying to convince
+  # us to accept. If a finalized header is present, it's the finalized
+  # header, otherwise it's the attested header
+  if update.finalized_header != BeaconBlockHeader():
+    update.finalized_header
+  else:
+    update.attested_header
+
+# https://github.com/ethereum/consensus-specs/blob/v1.1.7/specs/altair/sync-protocol.md#validate_light_client_update
+proc validate_light_client_update*(store: LightClientStore,
                                    update: LightClientUpdate,
+                                   current_slot: Slot,
                                    genesis_validators_root: Eth2Digest): bool =
-  # Verify update slot is larger than snapshot slot
-  if update.header.slot <= snapshot.header.slot:
+  # Verify update slot is larger than slot of current best finalized header
+  let active_header = get_active_header(update)
+  if not (current_slot >= active_header.slot and
+          active_header.slot > store.finalized_header.slot):
     return false
 
   # Verify update does not skip a sync committee period
   let
-    snapshot_period = sync_committee_period(snapshot.header.slot)
-    update_period = sync_committee_period(update.header.slot)
-  if update_period notin [snapshot_period, snapshot_period + 1]:
+    finalized_period =
+      compute_epoch_at_slot(store.finalized_header.slot) div
+        EPOCHS_PER_SYNC_COMMITTEE_PERIOD
+    update_period =
+      compute_epoch_at_slot(active_header.slot) div
+        EPOCHS_PER_SYNC_COMMITTEE_PERIOD
+
+  if update_period notin [finalized_period, finalized_period + 1]:
     return false
 
-  # Verify update header root is the finalized root of the finality header, if specified
-  # TODO: Use a view type instead of `unsafeAddr`
-  let signed_header = if update.finality_header.isZeroMemory:
+  # Verify that the `finalized_header`, if present, actually is the finalized
+  # header saved in the state of the `attested header`
+  if update.finalized_header.isZeroMemory:
     if not update.finality_branch.isZeroMemory:
       return false
-    unsafeAddr update.header
   else:
-    if not is_valid_merkle_branch(hash_tree_root(update.header),
+    if not is_valid_merkle_branch(hash_tree_root(update.finalized_header),
                                   update.finality_branch,
                                   log2trunc(FINALIZED_ROOT_INDEX),
                                   get_subtree_index(FINALIZED_ROOT_INDEX),
-                                  update.finality_header.state_root):
+                                  update.attested_header.state_root):
       return false
-    unsafeAddr update.finality_header
 
   # Verify update next sync committee if the update period incremented
   # TODO: Use a view type instead of `unsafeAddr`
-  let sync_committee = if update_period == snapshot_period:
+  let sync_committee = if update_period == finalized_period:
     if not update.next_sync_committee_branch.isZeroMemory:
       return false
-    unsafeAddr snapshot.current_sync_committee
+    unsafeAddr store.current_sync_committee
   else:
     if not is_valid_merkle_branch(hash_tree_root(update.next_sync_committee),
                                   update.next_sync_committee_branch,
                                   log2trunc(NEXT_SYNC_COMMITTEE_INDEX),
                                   get_subtree_index(NEXT_SYNC_COMMITTEE_INDEX),
-                                  update.header.state_root):
+                                  active_header.state_root):
       return false
-    unsafeAddr snapshot.next_sync_committee
+    unsafeAddr store.next_sync_committee
+
+  template sync_aggregate(): auto = update.sync_committee_aggregate
+  let sync_committee_participants_count = countOnes(sync_aggregate.sync_committee_bits)
 
-  let sync_committee_participants_count = countOnes(update.sync_committee_bits)
   # Verify sync committee has sufficient participants
   if sync_committee_participants_count < MIN_SYNC_COMMITTEE_PARTICIPANTS:
     return false
 
   # Verify sync committee aggregate signature
-  # participant_pubkeys = [pubkey for (bit, pubkey) in zip(update.sync_committee_bits, sync_committee.pubkeys) if bit]
+  # participant_pubkeys = [pubkey for (bit, pubkey) in zip(sync_aggregate.sync_committee_bits, sync_committee.pubkeys) if bit]
   var participant_pubkeys = newSeqOfCap[ValidatorPubKey](sync_committee_participants_count)
-  for idx, bit in update.sync_committee_bits:
+  for idx, bit in sync_aggregate.sync_committee_bits:
     if bit:
       participant_pubkeys.add(sync_committee.pubkeys[idx])
 
-  let domain = compute_domain(DOMAIN_SYNC_COMMITTEE, update.fork_version, genesis_validators_root)
-  let signing_root = compute_signing_root(signed_header[], domain)
+  let domain = compute_domain(
+    DOMAIN_SYNC_COMMITTEE, update.fork_version, genesis_validators_root)
+  let signing_root = compute_signing_root(update.attested_header, domain)
 
-  blsFastAggregateVerify(participant_pubkeys, signing_root.data, update.sync_committee_signature)
+  blsFastAggregateVerify(
+    participant_pubkeys, signing_root.data, sync_aggregate.sync_committee_signature)
 
-# https://github.com/ethereum/consensus-specs/blob/v1.1.6/specs/altair/sync-protocol.md#apply_light_client_update
-proc apply_light_client_update(snapshot: var LightClientSnapshot, update: LightClientUpdate) =
+# https://github.com/ethereum/consensus-specs/blob/v1.1.7/specs/altair/sync-protocol.md#apply_light_client_update
+func apply_light_client_update(
+    store: var LightClientStore, update: LightClientUpdate) =
   let
-    snapshot_period = sync_committee_period(snapshot.header.slot)
-    update_period = sync_committee_period(update.header.slot)
-  if update_period == snapshot_period + 1:
-    snapshot.current_sync_committee = snapshot.next_sync_committee
-    snapshot.next_sync_committee = update.next_sync_committee
-  snapshot.header = update.header
-
-# https://github.com/ethereum/consensus-specs/blob/v1.1.6/specs/altair/sync-protocol.md#process_light_client_update
+    active_header = get_active_header(update)
+    finalized_period =
+      compute_epoch_at_slot(store.finalized_header.slot) div
+        EPOCHS_PER_SYNC_COMMITTEE_PERIOD
+    update_period =
+      compute_epoch_at_slot(active_header.slot) div
+        EPOCHS_PER_SYNC_COMMITTEE_PERIOD
+  if update_period == finalized_period + 1:
+    store.current_sync_committee = store.next_sync_committee
+    store.next_sync_committee = update.next_sync_committee
+  store.finalized_header = active_header
+
+# https://github.com/ethereum/consensus-specs/blob/v1.1.7/specs/altair/sync-protocol.md#get_safety_threshold
+func get_safety_threshold(store: LightClientStore): uint64 =
+  max(
+    store.previous_max_active_participants,
+    store.current_max_active_participants
+  ) div 2
+
+# https://github.com/ethereum/consensus-specs/blob/v1.1.7/specs/altair/sync-protocol.md#process_light_client_update
 proc process_light_client_update*(store: var LightClientStore,
                                   update: LightClientUpdate,
                                   current_slot: Slot,
                                   genesis_validators_root: Eth2Digest): bool =
-  if not validate_light_client_update(store.snapshot, update, genesis_validators_root):
+  if not validate_light_client_update(
+      store, update, current_slot, genesis_validators_root):
     return false
-  store.valid_updates.incl(update)
-
-  var update_timeout = SLOTS_PER_EPOCH * EPOCHS_PER_SYNC_COMMITTEE_PERIOD
-  let sync_committee_participants_count = countOnes(update.sync_committee_bits)
-  if sync_committee_participants_count * 3 >= update.sync_committee_bits.len * 2 and
-     not update.finality_header.isZeroMemory:
-    # Apply update if (1) 2/3 quorum is reached and (2) we have a finality proof.
-    # Note that (2) means that the current light client design needs finality.
-    # It may be changed to re-organizable light client design. See the on-going issue consensus-specs#2182.
-    apply_light_client_update(store.snapshot, update)
-    store.valid_updates.clear()
-  elif current_slot > store.snapshot.header.slot + update_timeout:
-    var best_update_participants = 0
-    # TODO:
-    #  Use a view type to avoid the copying when a new best update
-    #  is discovered.
-    #  Alterantively, we could have a `set.max` operation returning
-    #  the best item as a `lent` value. We would need an `OrderedSet`
-    #  type with support for a custom comparison operation.
-    var best_update: LightClientUpdate
-    for update in store.valid_updates:
-      let update_participants = countOnes(update.sync_committee_bits)
-      if update_participants > best_update_participants:
-        best_update = update
-        best_update_participants = update_participants
-
-    # Forced best update when the update timeout has elapsed
-    apply_light_client_update(store.snapshot, best_update)
-    store.valid_updates.clear()
+
+  let
+    sync_committee_bits = update.sync_committee_aggregate.sync_committee_bits
+    sum_sync_committee_bits = countOnes(sync_committee_bits)
+
+  # Update the best update in case we have to force-update to it if the
+  # timeout elapses
+  if  store.best_valid_update.isNone or
+      sum_sync_committee_bits > countOnes(
+        store.best_valid_update.get.sync_committee_aggregate.sync_committee_bits):
+    store.best_valid_update = some(update)
+
+  # Track the maximum number of active participants in the committee signatures
+  store.current_max_active_participants = max(
+    store.current_max_active_participants,
+    sum_sync_committee_bits.uint64,
+  )
+
+  # Update the optimistic header
+  if  sum_sync_committee_bits.uint64 > get_safety_threshold(store) and
+      update.attested_header.slot > store.optimistic_header.slot:
+    store.optimistic_header = update.attested_header
+
+  # Update finalized header
+  if  sum_sync_committee_bits * 3 >= len(sync_committee_bits) * 2 and
+      update.finalized_header != default(BeaconBlockHeader):
+    # Normal update through 2/3 threshold
+    apply_light_client_update(store, update)
+    store.best_valid_update = none(LightClientUpdate)
+
   true