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error and progress codes for light client sync (#3490) 

When syncing as a light client, different behaviour is needed to handle
the various ways how errors may occur. The existing logic for blocks can
also be applied to light client objects:
- `Invalid`: Malformed object that is clearly an error by its producer.
- `MissingParent`: More data is needed to decide applicability.
- `UnviableFork`: Object may be valid but will never apply on this fork.
- `Duplicate`: No errors were encountered but the object was not useful.
This commit is contained in:
Etan Kissling 2022-03-14 10:25:54 +01:00 committed by GitHub
parent 276762958e
commit 29e5a4a752
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 109 additions and 63 deletions
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154
beacon_chain/spec/light_client_sync.nim
View File

@ -16,6 +16,8 @@ import
datatypes/altair,
helpers
from ../consensus_object_pools/block_pools_types import BlockError
func period_contains_fork_version(
cfg: RuntimeConfig,
period: SyncCommitteePeriod,
@ -67,9 +69,9 @@ func get_safety_threshold(store: LightClientStore): uint64 =
func initialize_light_client_store*(
trusted_block_root: Eth2Digest,
bootstrap: altair.LightClientBootstrap
): Opt[LightClientStore] =
): Result[LightClientStore, BlockError] =
if hash_tree_root(bootstrap.header) != trusted_block_root:
return err()
return err(BlockError.Invalid)
if not is_valid_merkle_branch(
hash_tree_root(bootstrap.current_sync_committee),
@ -77,7 +79,7 @@ func initialize_light_client_store*(
log2trunc(altair.CURRENT_SYNC_COMMITTEE_INDEX),
get_subtree_index(altair.CURRENT_SYNC_COMMITTEE_INDEX),
bootstrap.header.state_root):
return err()
return err(BlockError.Invalid)
return ok(LightClientStore(
finalized_header: bootstrap.header,
@ -90,37 +92,39 @@ proc validate_light_client_update*(
update: altair.LightClientUpdate,
current_slot: Slot,
cfg: RuntimeConfig,
genesis_validators_root: Eth2Digest): bool =
genesis_validators_root: Eth2Digest): Result[void, BlockError] =
# Verify sync committee has sufficient participants
template sync_aggregate(): auto = update.sync_aggregate
template sync_committee_bits(): auto = sync_aggregate.sync_committee_bits
let num_active_participants = countOnes(sync_committee_bits).uint64
if num_active_participants < MIN_SYNC_COMMITTEE_PARTICIPANTS:
return false
return err(BlockError.Invalid)
# Determine update header
template attested_header(): auto = update.attested_header
if current_slot < attested_header.slot:
return false
return err(BlockError.UnviableFork)
let active_header = get_active_header(update)
if attested_header.slot < active_header.slot:
return false
return err(BlockError.Invalid)
# Verify update is relevant
let is_next_sync_committee_known = not store.next_sync_committee.isZeroMemory
if is_next_sync_committee_known:
if active_header.slot < store.finalized_header.slot:
return false
return err(BlockError.Duplicate)
if active_header.slot == store.finalized_header.slot:
if attested_header.slot <= store.optimistic_header.slot:
return false
return err(BlockError.Duplicate)
# Verify update does not skip a sync committee period
let
finalized_period = store.finalized_header.slot.sync_committee_period
update_period = active_header.slot.sync_committee_period
if update_period notin [finalized_period, finalized_period + 1]:
return false
if update_period < finalized_period:
return err(BlockError.Duplicate)
if update_period > finalized_period + 1:
return err(BlockError.MissingParent)
let
is_signed_by_next_sync_committee =
update.next_sync_committee.isZeroMemory
@ -131,24 +135,24 @@ proc validate_light_client_update*(
update_period
current_period = current_slot.sync_committee_period
if current_period < signature_period:
return false
return err(BlockError.UnviableFork)
if is_next_sync_committee_known:
if signature_period notin [finalized_period, finalized_period + 1]:
return false
return err(BlockError.MissingParent)
else:
if signature_period != finalized_period:
return false
return err(BlockError.MissingParent)
# Verify fork version is acceptable
let fork_version = update.fork_version
if not cfg.period_contains_fork_version(signature_period, fork_version):
return false
return err(BlockError.UnviableFork)
# Verify that the `finalized_header`, if present, actually is the finalized
# header saved in the state of the `attested_header`
if not update.is_finality_update:
if not update.finality_branch.isZeroMemory:
return false
return err(BlockError.Invalid)
else:
if not is_valid_merkle_branch(
hash_tree_root(update.finalized_header),
@ -156,24 +160,24 @@ proc validate_light_client_update*(
log2trunc(altair.FINALIZED_ROOT_INDEX),
get_subtree_index(altair.FINALIZED_ROOT_INDEX),
update.attested_header.state_root):
return false
return err(BlockError.Invalid)
# Verify that the `next_sync_committee`, if present, actually is the
# next sync committee saved in the state of the `active_header`
if is_signed_by_next_sync_committee:
if not update.next_sync_committee_branch.isZeroMemory:
return false
return err(BlockError.Invalid)
else:
if update_period == finalized_period and is_next_sync_committee_known:
if update.next_sync_committee != store.next_sync_committee:
return false
return err(BlockError.UnviableFork)
if not is_valid_merkle_branch(
hash_tree_root(update.next_sync_committee),
update.next_sync_committee_branch,
log2trunc(altair.NEXT_SYNC_COMMITTEE_INDEX),
get_subtree_index(altair.NEXT_SYNC_COMMITTEE_INDEX),
active_header.state_root):
return false
return err(BlockError.Invalid)
# Verify sync committee aggregate signature
let sync_committee =
@ -193,9 +197,9 @@ proc validate_light_client_update*(
if not blsFastAggregateVerify(
participant_pubkeys, signing_root.data,
sync_aggregate.sync_committee_signature):
return false
return err(BlockError.Invalid)
true
ok()
# https://github.com/ethereum/consensus-specs/blob/vFuture/specs/altair/sync-protocol.md#validate_optimistic_light_client_update
proc validate_optimistic_light_client_update*(
@ -203,30 +207,32 @@ proc validate_optimistic_light_client_update*(
optimistic_update: OptimisticLightClientUpdate,
current_slot: Slot,
cfg: RuntimeConfig,
genesis_validators_root: Eth2Digest): bool =
genesis_validators_root: Eth2Digest): Result[void, BlockError] =
# Verify sync committee has sufficient participants
template sync_aggregate(): auto = optimistic_update.sync_aggregate
template sync_committee_bits(): auto = sync_aggregate.sync_committee_bits
let num_active_participants = countOnes(sync_committee_bits).uint64
if num_active_participants < MIN_SYNC_COMMITTEE_PARTICIPANTS:
return false
return err(BlockError.Invalid)
# Determine update header
template attested_header(): auto = optimistic_update.attested_header
if current_slot < attested_header.slot:
return false
return err(BlockError.Invalid)
template active_header(): auto = attested_header
# Verify update is relevant
if attested_header.slot <= store.optimistic_header.slot:
return false
return err(BlockError.Duplicate)
# Verify update does not skip a sync committee period
let
finalized_period = store.finalized_header.slot.sync_committee_period
update_period = active_header.slot.sync_committee_period
if update_period notin [finalized_period, finalized_period + 1]:
return false
if update_period < finalized_period:
return err(BlockError.Duplicate)
if update_period > finalized_period + 1:
return err(BlockError.MissingParent)
let
is_signed_by_next_sync_committee =
optimistic_update.is_signed_by_next_sync_committee
@ -237,19 +243,19 @@ proc validate_optimistic_light_client_update*(
update_period
current_period = current_slot.sync_committee_period
if current_period < signature_period:
return false
return err(BlockError.Invalid)
let is_next_sync_committee_known = not store.next_sync_committee.isZeroMemory
if is_next_sync_committee_known:
if signature_period notin [finalized_period, finalized_period + 1]:
return false
return err(BlockError.MissingParent)
else:
if signature_period != finalized_period:
return false
return err(BlockError.MissingParent)
# Verify fork version is acceptable
let fork_version = optimistic_update.fork_version
if not cfg.period_contains_fork_version(signature_period, fork_version):
return false
return err(BlockError.UnviableFork)
# Verify sync committee aggregate signature
let sync_committee =
@ -269,14 +275,15 @@ proc validate_optimistic_light_client_update*(
if not blsFastAggregateVerify(
participant_pubkeys, signing_root.data,
sync_aggregate.sync_committee_signature):
return false
return err(BlockError.Invalid)
true
ok()
# https://github.com/ethereum/consensus-specs/blob/vFuture/specs/altair/sync-protocol.md#apply_light_client_update
func apply_light_client_update(
store: var LightClientStore,
update: altair.LightClientUpdate) =
update: altair.LightClientUpdate): bool =
var didProgress = false
let
active_header = get_active_header(update)
finalized_period = store.finalized_header.slot.sync_committee_period
@ -284,6 +291,7 @@ func apply_light_client_update(
if store.next_sync_committee.isZeroMemory:
assert update_period == finalized_period
store.next_sync_committee = update.next_sync_committee
didProgress = true
elif update_period == finalized_period + 1:
store.previous_max_active_participants =
store.current_max_active_participants
@ -291,29 +299,52 @@ func apply_light_client_update(
store.current_sync_committee = store.next_sync_committee
store.next_sync_committee = update.next_sync_committee
assert not store.next_sync_committee.isZeroMemory
didProgress = true
if active_header.slot > store.finalized_header.slot:
store.finalized_header = active_header
didProgress = true
didProgress
# https://github.com/ethereum/consensus-specs/blob/vFuture/specs/altair/sync-protocol.md#apply_optimistic_light_client_header
func apply_optimistic_light_client_header(
store: var LightClientStore,
attested_header: BeaconBlockHeader,
num_active_participants: uint64) =
num_active_participants: uint64): bool =
var didProgress = false
if store.current_max_active_participants < num_active_participants:
store.current_max_active_participants = num_active_participants
if num_active_participants > get_safety_threshold(store) and
attested_header.slot > store.optimistic_header.slot:
store.optimistic_header = attested_header
didProgress = true
didProgress
# https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/altair/sync-protocol.md#process_slot_for_light_client_store
type
ProcessSlotForLightClientStoreResult* = enum
NoUpdate,
UpdatedWithoutSupermajority,
UpdatedWithoutFinalityProof
func process_slot_for_light_client_store*(
store: var LightClientStore,
current_slot: Slot) =
current_slot: Slot): ProcessSlotForLightClientStoreResult {.discardable.} =
var res = NoUpdate
if store.best_valid_update.isSome and
current_slot > store.finalized_header.slot + UPDATE_TIMEOUT:
apply_light_client_update(store, store.best_valid_update.get)
template sync_aggregate(): auto = store.best_valid_update.get.sync_aggregate
template sync_committee_bits(): auto = sync_aggregate.sync_committee_bits
let num_active_participants = countOnes(sync_committee_bits).uint64
if apply_light_client_update(store, store.best_valid_update.get):
if num_active_participants * 3 < static(sync_committee_bits.len * 2):
res = UpdatedWithoutSupermajority
else:
res = UpdatedWithoutFinalityProof
store.best_valid_update = none(altair.LightClientUpdate)
res
# https://github.com/ethereum/consensus-specs/blob/vFuture/specs/altair/sync-protocol.md#process_light_client_update
proc process_light_client_update*(
@ -322,18 +353,20 @@ proc process_light_client_update*(
current_slot: Slot,
cfg: RuntimeConfig,
genesis_validators_root: Eth2Digest,
allowForceUpdate = true): bool =
if not validate_light_client_update(
store, update, current_slot, cfg, genesis_validators_root):
return false
allowForceUpdate = true): Result[void, BlockError] =
? validate_light_client_update(
store, update, current_slot, cfg, genesis_validators_root)
var didProgress = false
template sync_aggregate(): auto = update.sync_aggregate
template sync_committee_bits(): auto = sync_aggregate.sync_committee_bits
let num_active_participants = countOnes(sync_committee_bits).uint64
# Update the optimistic header
apply_optimistic_light_client_header(
store, update.attested_header, num_active_participants)
if apply_optimistic_light_client_header(
store, update.attested_header, num_active_participants):
didProgress = true
# Update the best update in case we have to force-update to it
# if the timeout elapses
@ -346,19 +379,27 @@ proc process_light_client_update*(
countOnes(best_sync_aggregate.sync_committee_bits).uint64
if num_active_participants > best_active_participants:
store.best_valid_update = some(update)
didProgress = true
# Update finalized header
if num_active_participants * 3 >= static(sync_committee_bits.len * 2) and
update.is_finality_update:
# Normal update through 2/3 threshold
apply_light_client_update(store, update)
if apply_light_client_update(store, update):
didProgress = true
store.best_valid_update = none(altair.LightClientUpdate)
else:
if allowForceUpdate:
# Force-update to best update if the timeout elapsed
process_slot_for_light_client_store(store, current_slot)
case process_slot_for_light_client_store(store, current_slot)
of UpdatedWithoutSupermajority, UpdatedWithoutFinalityProof:
didProgress = true
of NoUpdate: discard
true
if not didProgress:
err(BlockError.Duplicate)
else:
ok()
# https://github.com/ethereum/consensus-specs/blob/vFuture/specs/altair/sync-protocol.md#process_light_client_update
proc process_optimistic_light_client_update*(
@ -366,17 +407,22 @@ proc process_optimistic_light_client_update*(
optimistic_update: OptimisticLightClientUpdate,
current_slot: Slot,
cfg: RuntimeConfig,
genesis_validators_root: Eth2Digest): bool =
if not validate_optimistic_light_client_update(
store, optimistic_update, current_slot, cfg, genesis_validators_root):
return false
genesis_validators_root: Eth2Digest): Result[void, BlockError] =
? validate_optimistic_light_client_update(
store, optimistic_update, current_slot, cfg, genesis_validators_root)
var didProgress = false
template sync_aggregate(): auto = optimistic_update.sync_aggregate
template sync_committee_bits(): auto = sync_aggregate.sync_committee_bits
let num_active_participants = countOnes(sync_committee_bits).uint64
# Update the optimistic header
apply_optimistic_light_client_header(
store, optimistic_update.attested_header, num_active_participants)
if apply_optimistic_light_client_header(
store, optimistic_update.attested_header, num_active_participants):
didProgress = true
true
if not didProgress:
err(BlockError.Duplicate)
else:
ok()

8
tests/consensus_spec/altair/test_fixture_sync_protocol.nim
View File

@ -151,7 +151,7 @@ suite "EF - Altair - Unittests - Sync protocol" & preset():
store, update, signature_slot, cfg, state.genesis_validators_root)
check:
res
res.isOk
store.current_max_active_participants > 0
store.optimistic_header == update.attested_header
store.finalized_header == pre_store_finalized_header
@ -214,7 +214,7 @@ suite "EF - Altair - Unittests - Sync protocol" & preset():
store, update, signature_slot, cfg, state.genesis_validators_root)
check:
res
res.isOk
store.current_max_active_participants > 0
store.optimistic_header == update.attested_header
store.finalized_header == pre_store_finalized_header
@ -277,7 +277,7 @@ suite "EF - Altair - Unittests - Sync protocol" & preset():
store, update, signature_slot, cfg, state.genesis_validators_root)
check:
res
res.isOk
store.previous_max_active_participants > 0
store.optimistic_header == update.attested_header
store.finalized_header == update.attested_header
@ -370,7 +370,7 @@ suite "EF - Altair - Unittests - Sync protocol" & preset():
store, update, signature_slot, cfg, state.genesis_validators_root)
check:
res
res.isOk
store.current_max_active_participants > 0
store.optimistic_header == update.attested_header
store.finalized_header == update.finalized_header

4
tests/consensus_spec/altair/test_fixture_sync_protocol_light_client_sync.nim
View File

@ -121,12 +121,12 @@ proc runTest(identifier: string) =
let res = process_light_client_update(
store, step.update, step.current_slot,
cfg, genesis_validators_root)
check res
check res.isOk
of TestStepKind.ProcessOptimisticUpdate:
let res = process_optimistic_light_client_update(
store, step.optimistic_update, step.current_slot,
cfg, genesis_validators_root)
check res
check res.isOk
check:
store.finalized_header == expected_finalized_header

6
tests/test_light_client.nim
View File

@ -128,7 +128,7 @@ suite "Light client" & preset():
check bootstrap.isSome
var storeRes = initialize_light_client_store(
trusted_block_root, bootstrap.get)
check storeRes.isSome
check storeRes.isOk
template store(): auto = storeRes.get
# Sync to latest sync committee period
@ -146,7 +146,7 @@ suite "Light client" & preset():
check:
bestUpdate.isSome
bestUpdate.get.finalized_header.slot.sync_committee_period == period
res
res.isOk
store.finalized_header == bestUpdate.get.finalized_header
inc numIterations
if numIterations > 20: doAssert false # Avoid endless loop on test failure
@ -159,7 +159,7 @@ suite "Light client" & preset():
check:
latestUpdate.isSome
latestUpdate.get.attested_header.slot == dag.headState.blck.parent.slot
res
res.isOk
store.finalized_header == latestUpdate.get.finalized_header
store.optimistic_header == latestUpdate.get.attested_header