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reintroduce finalization verification to beacon node, because otherwise the consensus layer can get detached without noticing it (#1013)

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tersec 2020-05-13 08:36:33 +00:00 committed by GitHub
parent da0b1a4993
commit 9ad05d44e4
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1 changed files with 25 additions and 2 deletions
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27
beacon_chain/beacon_node.nim
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@ -315,6 +315,25 @@ proc onBeaconBlock(node: BeaconNode, signedBlock: SignedBeaconBlock) =
# don't know if it's part of the chain we're currently building. # don't know if it's part of the chain we're currently building.
discard node.storeBlock(signedBlock) discard node.storeBlock(signedBlock)
func verifyFinalization(node: BeaconNode, slot: Slot) =
# Epoch must be >= 4 to check finalization
const SETTLING_TIME_OFFSET = 1'u64
let epoch = slot.compute_epoch_at_slot()
# Don't static-assert this -- if this isn't called, don't require it
doAssert SLOTS_PER_EPOCH > SETTLING_TIME_OFFSET
# Intentionally, loudly assert. Point is to fail visibly and unignorably
# during testing.
if epoch >= 4 and slot mod SLOTS_PER_EPOCH > SETTLING_TIME_OFFSET:
let finalizedEpoch =
node.blockPool.finalizedHead.blck.slot.compute_epoch_at_slot()
# Finalization rule 234, that has the most lag slots among the cases, sets
# state.finalized_checkpoint = old_previous_justified_checkpoint.epoch + 3
# and then state.slot gets incremented, to increase the maximum offset, if
# finalization occurs every slot, to 4 slots vs scheduledSlot.
doAssert finalizedEpoch + 4 >= epoch
proc onSlotStart(node: BeaconNode, lastSlot, scheduledSlot: Slot) {.gcsafe, async.} = proc onSlotStart(node: BeaconNode, lastSlot, scheduledSlot: Slot) {.gcsafe, async.} =
## Called at the beginning of a slot - usually every slot, but sometimes might ## Called at the beginning of a slot - usually every slot, but sometimes might
## skip a few in case we're running late. ## skip a few in case we're running late.
@ -343,8 +362,9 @@ proc onSlotStart(node: BeaconNode, lastSlot, scheduledSlot: Slot) {.gcsafe, asyn
cat = "scheduling" cat = "scheduling"
# Check before any re-scheduling of onSlotStart() # Check before any re-scheduling of onSlotStart()
if node.config.stopAtEpoch > 0'u64 and # Offset backwards slightly to allow this epoch's finalization check to occur
scheduledSlot.compute_epoch_at_slot() >= node.config.stopAtEpoch: if scheduledSlot > 3 and node.config.stopAtEpoch > 0'u64 and
(scheduledSlot - 3).compute_epoch_at_slot() >= node.config.stopAtEpoch:
info "Stopping at pre-chosen epoch", info "Stopping at pre-chosen epoch",
chosenEpoch = node.config.stopAtEpoch, chosenEpoch = node.config.stopAtEpoch,
epoch = scheduledSlot.compute_epoch_at_slot(), epoch = scheduledSlot.compute_epoch_at_slot(),
@ -381,6 +401,9 @@ proc onSlotStart(node: BeaconNode, lastSlot, scheduledSlot: Slot) {.gcsafe, asyn
beacon_slot.set slot.int64 beacon_slot.set slot.int64
if node.config.verifyFinalization:
verifyFinalization(node, scheduledSlot)
if slot > lastSlot + SLOTS_PER_EPOCH: if slot > lastSlot + SLOTS_PER_EPOCH:
# We've fallen behind more than an epoch - there's nothing clever we can # We've fallen behind more than an epoch - there's nothing clever we can
# do here really, except skip all the work and try again later. # do here really, except skip all the work and try again later.