# beacon_chain # Copyright (c) 2018-2021 Status Research & Development GmbH # Licensed and distributed under either of # * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT). # * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0). # at your option. This file may not be copied, modified, or distributed except according to those terms. import # Standard library std/[os, osproc, random, sequtils, streams, tables], # Nimble packages stew/[assign2, objects, shims/macros], chronos, metrics, json_rpc/[rpcserver, jsonmarshal], chronicles, json_serialization/std/[options, sets, net], serialization/errors, eth/db/kvstore, eth/[keys, async_utils], eth/p2p/discoveryv5/[protocol, enr], # Local modules ./spec/[ datatypes, digest, crypto, helpers, network, signatures, state_transition, validator], ./conf, ./time, ./validator_pool, ./attestation_pool, ./exit_pool, ./block_pools/[spec_cache, chain_dag, clearance], ./eth2_network, ./keystore_management, ./beacon_node_common, ./beacon_node_types, ./nimbus_binary_common, ./eth1_monitor, ./version, ./ssz/merkleization, ./attestation_aggregation, ./sync_manager, ./sszdump, ./validator_slashing_protection # Metrics for tracking attestation and beacon block loss const delayBuckets = [-Inf, -4.0, -2.0, -1.0, -0.5, -0.1, -0.05, 0.05, 0.1, 0.5, 1.0, 2.0, 4.0, 8.0, Inf] declareCounter beacon_attestations_sent, "Number of beacon chain attestations sent by this peer" declareHistogram beacon_attestation_sent_delay, "Time(s) between slot start and attestation sent moment", buckets = delayBuckets declareCounter beacon_blocks_proposed, "Number of beacon chain blocks sent by this peer" declareGauge(attached_validator_balance, "Validator balance at slot end of the first 64 validators, in Gwei", labels = ["pubkey"]) declarePublicGauge(attached_validator_balance_total, "Validator balance of all attached validators, in Gwei") logScope: topics = "beacval" proc findValidator(state: BeaconState, pubKey: ValidatorPubKey): Option[ValidatorIndex] = let idx = state.validators.asSeq.findIt(it.pubKey == pubKey) if idx == -1: # We allow adding a validator even if its key is not in the state registry: # it might be that the deposit for this validator has not yet been processed notice "Validator deposit not yet processed, monitoring", pubKey none(ValidatorIndex) else: some(idx.ValidatorIndex) proc addLocalValidator*(node: BeaconNode, state: BeaconState, privKey: ValidatorPrivKey) = let pubKey = privKey.toPubKey() node.attachedValidators.addLocalValidator( pubKey, privKey, findValidator(state, pubKey)) proc addLocalValidators*(node: BeaconNode) = for validatorKey in node.config.validatorKeys: node.addLocalValidator node.chainDag.headState.data.data, validatorKey proc addRemoteValidators*(node: BeaconNode) = # load all the validators from the child process - loop until `end` var line = newStringOfCap(120).TaintedString while line != "end" and running(node.vcProcess): if node.vcProcess.outputStream.readLine(line) and line != "end": let key = ValidatorPubKey.fromHex(line).get() index = findValidator(node.chainDag.headState.data.data, key) let v = AttachedValidator(pubKey: key, index: index, kind: ValidatorKind.remote, connection: ValidatorConnection( inStream: node.vcProcess.inputStream, outStream: node.vcProcess.outputStream, pubKeyStr: $key)) node.attachedValidators.addRemoteValidator(key, v) proc getAttachedValidator*(node: BeaconNode, pubkey: ValidatorPubKey): AttachedValidator = node.attachedValidators.getValidator(pubkey) proc getAttachedValidator*(node: BeaconNode, state: BeaconState, idx: ValidatorIndex): AttachedValidator = if idx < state.validators.len.ValidatorIndex: let validator = node.getAttachedValidator(state.validators[idx].pubkey) if validator != nil and validator.index != some(idx.ValidatorIndex): # Update index, in case the validator was activated! notice "Validator activated", pubkey = validator.pubkey, index = idx validator.index = some(idx.ValidatorIndex) validator else: warn "Validator index out of bounds", idx, stateSlot = state.slot, validators = state.validators.len nil proc getAttachedValidator*(node: BeaconNode, epochRef: EpochRef, idx: ValidatorIndex): AttachedValidator = if idx < epochRef.validator_keys.len.ValidatorIndex: let validator = node.getAttachedValidator(epochRef.validator_keys[idx]) if validator != nil and validator.index != some(idx.ValidatorIndex): # Update index, in case the validator was activated! notice "Validator activated", pubkey = validator.pubkey, index = idx validator.index = some(idx.ValidatorIndex) validator else: warn "Validator index out of bounds", idx, epoch = epochRef.epoch, validators = epochRef.validator_keys.len nil proc isSynced*(node: BeaconNode, head: BlockRef): bool = ## TODO This function is here as a placeholder for some better heurestics to ## determine if we're in sync and should be producing blocks and ## attestations. Generally, the problem is that slot time keeps advancing ## even when there are no blocks being produced, so there's no way to ## distinguish validators geniunely going missing from the node not being ## well connected (during a network split or an internet outage for ## example). It would generally be correct to simply keep running as if ## we were the only legit node left alive, but then we run into issues: ## with enough many empty slots, the validator pool is emptied leading ## to empty committees and lots of empty slot processing that will be ## thrown away as soon as we're synced again. let # The slot we should be at, according to the clock beaconTime = node.beaconClock.now() wallSlot = beaconTime.toSlot() # TODO: MaxEmptySlotCount should likely involve the weak subjectivity period. # TODO if everyone follows this logic, the network will not recover from a # halt: nobody will be producing blocks because everone expects someone # else to do it if wallSlot.afterGenesis and head.slot + MaxEmptySlotCount < wallSlot.slot: false else: true proc sendAttestation*( node: BeaconNode, attestation: Attestation, num_active_validators: uint64) = let subnet_index = compute_subnet_for_attestation( get_committee_count_per_slot(num_active_validators), attestation.data.slot, attestation.data.index.CommitteeIndex) node.network.broadcast( getAttestationTopic(node.forkDigest, subnet_index), attestation) # Ensure node's own broadcast attestations end up in its attestation pool discard node.processor[].attestationValidator( attestation, subnet_index, false) beacon_attestations_sent.inc() proc sendVoluntaryExit*(node: BeaconNode, exit: SignedVoluntaryExit) = node.network.broadcast(getVoluntaryExitsTopic(node.forkDigest), exit) proc sendAttesterSlashing*(node: BeaconNode, slashing: AttesterSlashing) = node.network.broadcast(getAttesterSlashingsTopic(node.forkDigest), slashing) proc sendProposerSlashing*(node: BeaconNode, slashing: ProposerSlashing) = node.network.broadcast(getProposerSlashingsTopic(node.forkDigest), slashing) proc sendAttestation*(node: BeaconNode, attestation: Attestation) = # For the validator API, which doesn't supply num_active_validators. let attestationBlck = node.chainDag.getRef(attestation.data.beacon_block_root) if attestationBlck.isNil: debug "Attempt to send attestation without corresponding block" return node.sendAttestation( attestation, count_active_validators( node.chainDag.getEpochRef(attestationBlck, attestation.data.target.epoch))) proc createAndSendAttestation(node: BeaconNode, fork: Fork, genesis_validators_root: Eth2Digest, validator: AttachedValidator, attestationData: AttestationData, committeeLen: int, indexInCommittee: int, num_active_validators: uint64) {.async.} = var attestation = await validator.produceAndSignAttestation( attestationData, committeeLen, indexInCommittee, fork, genesis_validators_root) node.sendAttestation(attestation, num_active_validators) if node.config.dumpEnabled: dump(node.config.dumpDirOutgoing, attestation.data, validator.pubKey) let wallTime = node.beaconClock.now() let deadline = attestationData.slot.toBeaconTime() + seconds(int(SECONDS_PER_SLOT div 3)) let (delayStr, delayMillis) = if wallTime < deadline: ("-" & $(deadline - wallTime), -toFloatSeconds(deadline - wallTime)) else: ($(wallTime - deadline), toFloatSeconds(wallTime - deadline)) notice "Attestation sent", attestation = shortLog(attestation), validator = shortLog(validator), delay = delayStr, indexInCommittee = indexInCommittee beacon_attestation_sent_delay.observe(delayMillis) proc getBlockProposalEth1Data*(node: BeaconNode, state: BeaconState): BlockProposalEth1Data = if node.eth1Monitor.isNil: var pendingDepositsCount = state.eth1_data.deposit_count - state.eth1_deposit_index if pendingDepositsCount > 0: result.hasMissingDeposits = true else: result.vote = state.eth1_data else: let finalizedEpochRef = node.chainDag.getFinalizedEpochRef() result = node.eth1Monitor.getBlockProposalData( state, finalizedEpochRef.eth1_data, finalizedEpochRef.eth1_deposit_index) proc makeBeaconBlockForHeadAndSlot*(node: BeaconNode, randao_reveal: ValidatorSig, validator_index: ValidatorIndex, graffiti: GraffitiBytes, head: BlockRef, slot: Slot): Option[BeaconBlock] = # Advance state to the slot that we're proposing for node.chainDag.withState(node.chainDag.tmpState, head.atSlot(slot)): let eth1Proposal = node.getBlockProposalEth1Data(state) poolPtr = unsafeAddr node.chainDag # safe because restore is short-lived if eth1Proposal.hasMissingDeposits: error "Eth1 deposits not available. Skipping block proposal", slot return none(BeaconBlock) func restore(v: var HashedBeaconState) = # TODO address this ugly workaround - there should probably be a # `state_transition` that takes a `StateData` instead and updates # the block as well doAssert v.addr == addr poolPtr.tmpState.data assign(poolPtr.tmpState, poolPtr.headState) makeBeaconBlock( node.runtimePreset, hashedState, validator_index, head.root, randao_reveal, eth1Proposal.vote, graffiti, node.attestationPool[].getAttestationsForBlock(state, cache), eth1Proposal.deposits, node.exitPool[].getProposerSlashingsForBlock(), node.exitPool[].getAttesterSlashingsForBlock(), node.exitPool[].getVoluntaryExitsForBlock(), restore, cache) proc proposeSignedBlock*(node: BeaconNode, head: BlockRef, validator: AttachedValidator, newBlock: SignedBeaconBlock): BlockRef = let newBlockRef = node.chainDag.addRawBlock(node.quarantine, newBlock) do ( blckRef: BlockRef, trustedBlock: TrustedSignedBeaconBlock, epochRef: EpochRef, state: HashedBeaconState): # Callback add to fork choice if signed block valid (and becomes trusted) node.attestationPool[].addForkChoice( epochRef, blckRef, trustedBlock.message, node.beaconClock.now().slotOrZero()) if newBlockRef.isErr: warn "Unable to add proposed block to block pool", newBlock = shortLog(newBlock.message), blockRoot = shortLog(newBlock.root) return head notice "Block proposed", blck = shortLog(newBlock.message), blockRoot = shortLog(newBlockRef[].root), validator = shortLog(validator) if node.config.dumpEnabled: dump(node.config.dumpDirOutgoing, newBlock) node.network.broadcast(node.topicBeaconBlocks, newBlock) beacon_blocks_proposed.inc() return newBlockRef[] proc proposeBlock(node: BeaconNode, validator: AttachedValidator, validator_index: ValidatorIndex, head: BlockRef, slot: Slot): Future[BlockRef] {.async.} = if head.slot >= slot: # We should normally not have a head newer than the slot we're proposing for # but this can happen if block proposal is delayed warn "Skipping proposal, have newer head already", headSlot = shortLog(head.slot), headBlockRoot = shortLog(head.root), slot = shortLog(slot) return head let notSlashable = node.attachedValidators .slashingProtection .checkSlashableBlockProposal(validator.pubkey, slot) if notSlashable.isErr: warn "Slashing protection activated", validator = validator.pubkey, slot = slot, existingProposal = notSlashable.error return head let fork = node.chainDag.headState.data.data.fork genesis_validators_root = node.chainDag.headState.data.data.genesis_validators_root let randao = await validator.genRandaoReveal( fork, genesis_validators_root, slot) message = makeBeaconBlockForHeadAndSlot( node, randao, validator_index, node.graffitiBytes, head, slot) if not message.isSome(): return head # already logged elsewhere! var newBlock = SignedBeaconBlock( message: message.get() ) newBlock.root = hash_tree_root(newBlock.message) # TODO: recomputed in block proposal let signing_root = compute_block_root( fork, genesis_validators_root, slot, newBlock.root) node.attachedValidators .slashingProtection .registerBlock(validator.pubkey, slot, signing_root) newBlock.signature = await validator.signBlockProposal( fork, genesis_validators_root, slot, newBlock.root) return node.proposeSignedBlock(head, validator, newBlock) proc handleAttestations(node: BeaconNode, head: BlockRef, slot: Slot) = ## Perform all attestations that the validators attached to this node should ## perform during the given slot if slot + SLOTS_PER_EPOCH < head.slot: # The latest block we know about is a lot newer than the slot we're being # asked to attest to - this makes it unlikely that it will be included # at all. # TODO the oldest attestations allowed are those that are older than the # finalized epoch.. also, it seems that posting very old attestations # is risky from a slashing perspective. More work is needed here. warn "Skipping attestation, head is too recent", headSlot = shortLog(head.slot), slot = shortLog(slot) return let attestationHead = head.atSlot(slot) if head != attestationHead.blck: # In rare cases, such as when we're busy syncing or just slow, we'll be # attesting to a past state - we must then recreate the world as it looked # like back then notice "Attesting to a state in the past, falling behind?", headSlot = shortLog(head.slot), attestationHeadSlot = shortLog(attestationHead.slot), attestationSlot = shortLog(slot) trace "Checking attestations", attestationHeadRoot = shortLog(attestationHead.blck.root), attestationSlot = shortLog(slot) # Collect data to send before node.stateCache grows stale var attestations: seq[tuple[ data: AttestationData, committeeLen, indexInCommittee: int, validator: AttachedValidator]] # We need to run attestations exactly for the slot that we're attesting to. # In case blocks went missing, this means advancing past the latest block # using empty slots as fillers. # https://github.com/ethereum/eth2.0-specs/blob/v1.0.0/specs/phase0/validator.md#validator-assignments let epochRef = node.chainDag.getEpochRef( attestationHead.blck, slot.compute_epoch_at_slot()) committees_per_slot = get_committee_count_per_slot(epochRef) num_active_validators = count_active_validators(epochRef) fork = node.chainDag.headState.data.data.fork genesis_validators_root = node.chainDag.headState.data.data.genesis_validators_root for committee_index in 0'u64.. # SECONDS_PER_SLOT / ATTESTATION_ENTROPY_DIVISOR, which will # enure that the second condition can't go negative. static: doAssert ATTESTATION_ENTROPY_DIVISOR > ATTESTATION_PRODUCTION_DIVISOR # For each `slot`, a validator must generate a uniform random variable # `slot_timing_entropy` between `(-SECONDS_PER_SLOT / # ATTESTATION_ENTROPY_DIVISOR, SECONDS_PER_SLOT / # ATTESTATION_ENTROPY_DIVISOR)` with millisecond resolution and using local # entropy. # # Per issue discussion "validators served by the same beacon node can have # the same attestation production time, i.e., they can share the source of # the entropy and the actual slot_timing_entropy value." const slot_timing_entropy_upper_bound = SECONDS_PER_SLOT.int64 * 1000 div ATTESTATION_ENTROPY_DIVISOR slot_timing_entropy_lower_bound = 0-slot_timing_entropy_upper_bound rand(range[(slot_timing_entropy_lower_bound + 1) .. (slot_timing_entropy_upper_bound - 1)]) proc updateValidatorMetrics*(node: BeaconNode) = when defined(metrics): # Technically, this only needs to be done on epoch transitions and if there's # a reorg that spans an epoch transition, but it's easier to implement this # way for now.. # We'll limit labelled metrics to the first 64, so that we don't overload # prom template state: untyped = node.chainDag.headState.data.data var total: Gwei var i = 0 for _, v in node.attachedValidators.validators: let balance = if v.index.isNone(): 0.Gwei elif v.index.get().uint64 >= state.balances.lenu64: debug "Cannot get validator balance, index out of bounds", pubkey = shortLog(v.pubkey), index = v.index.get(), balances = state.balances.len, stateRoot = node.chainDag.headState.data.root 0.Gwei else: state.balances[v.index.get()] if i < 64: attached_validator_balance.set( min(balance, int64.high.uint64).int64, labelValues = [shortLog(v.pubkey)]) else: inc i total += balance node.attachedValidatorBalanceTotal = total attached_validator_balance_total.set(min(total, int64.high.uint64).int64) else: discard proc handleValidatorDuties*(node: BeaconNode, lastSlot, slot: Slot) {.async.} = ## Perform validator duties - create blocks, vote and aggregate existing votes if node.attachedValidators.count == 0: # Nothing to do because we have no validator attached return # The chainDag head might be updated by sync while we're working due to the # await calls, thus we use a local variable to keep the logic straight here var head = node.chainDag.head if not node.isSynced(head): notice "Syncing in progress; skipping validator duties for now", slot, headSlot = head.slot # Rewards will be growing though, as we sync.. updateValidatorMetrics(node) return var curSlot = lastSlot + 1 # If broadcastStartEpoch is 0, it hasn't had time to initialize yet, which # means that it'd be okay not to continue, but it won't gossip regardless. if curSlot.epoch < node.processor[].doppelgangerDetection.broadcastStartEpoch and node.config.doppelgangerDetection: debug "Waiting to gossip out to detect potential duplicate validators", broadcastStartEpoch = node.processor[].doppelgangerDetection.broadcastStartEpoch return # Start by checking if there's work we should have done in the past that we # can still meaningfully do while curSlot < slot: notice "Catching up on validator duties", curSlot = shortLog(curSlot), lastSlot = shortLog(lastSlot), slot = shortLog(slot) # For every slot we're catching up, we'll propose then send # attestations - head should normally be advancing along the same branch # in this case head = await handleProposal(node, head, curSlot) # For each slot we missed, we need to send out attestations - if we were # proposing during this time, we'll use the newly proposed head, else just # keep reusing the same - the attestation that goes out will actually # rewind the state to what it looked like at the time of that slot handleAttestations(node, head, curSlot) curSlot += 1 head = await handleProposal(node, head, slot) # Fix timing attack: https://github.com/ethereum/eth2.0-specs/pull/2101 # A validator must create and broadcast the `attestation` to the associated # attestation subnet when the earlier one of the following two events occurs: # # - The validator has received a valid block from the expected block # proposer for the assigned `slot`. In this case, the validator must set a # timer for `abs(slot_timing_entropy)`. The end of this timer will be the # trigger for attestation production. # # - `SECONDS_PER_SLOT / ATTESTATION_PRODUCTION_DIVISOR + # slot_timing_entropy` seconds have elapsed since the start of the `slot` # (using the `slot_timing_entropy` generated for this slot) # We've been doing lots of work up until now which took time. Normally, we # send out attestations at the slot thirds-point, so we go back to the clock # to see how much time we need to wait. # TODO the beacon clock might jump here also. It's probably easier to complete # the work for the whole slot using a monotonic clock instead, then deal # with any clock discrepancies once only, at the start of slot timer # processing.. let slotTimingEntropy = getSlotTimingEntropy() template sleepToSlotOffsetWithHeadUpdate(extra: chronos.Duration, msg: static string) = let waitTime = node.beaconClock.fromNow(slot.toBeaconTime(extra)) if waitTime.inFuture: discard await withTimeout( node.processor[].blockReceivedDuringSlot, waitTime.offset) # Might have gotten a valid beacon block this slot, which triggers the # first case, in which we wait for another abs(slotTimingEntropy). if node.processor[].blockReceivedDuringSlot.finished: await sleepAsync( milliseconds(max(slotTimingEntropy, 0 - slotTimingEntropy))) # Time passed - we might need to select a new head in that case node.processor[].updateHead(slot) head = node.chainDag.head sleepToSlotOffsetWithHeadUpdate( milliseconds(SECONDS_PER_SLOT.int64 * 1000 div ATTESTATION_PRODUCTION_DIVISOR + slotTimingEntropy), "Waiting to send attestations") handleAttestations(node, head, slot) updateValidatorMetrics(node) # the important stuff is done, update the vanity numbers # https://github.com/ethereum/eth2.0-specs/blob/v1.0.0/specs/phase0/validator.md#broadcast-aggregate # If the validator is selected to aggregate (is_aggregator), then they # broadcast their best aggregate as a SignedAggregateAndProof to the global # aggregate channel (beacon_aggregate_and_proof) two-thirds of the way # through the slot-that is, SECONDS_PER_SLOT * 2 / 3 seconds after the start # of slot. if slot > 2: discard await node.beaconClock.sleepToSlotOffset( seconds(int64(SECONDS_PER_SLOT * 2) div 3), slot, "Waiting to aggregate attestations") await broadcastAggregatedAttestations(node, head, slot) if node.eth1Monitor != nil and (slot mod SLOTS_PER_EPOCH) == 0: let finalizedEpochRef = node.chainDag.getFinalizedEpochRef() discard node.eth1Monitor.trackFinalizedState( finalizedEpochRef.eth1_data, finalizedEpochRef.eth1_deposit_index)