nimbus-eth2/beacon_chain/attestation_pool.nim

348 lines
13 KiB
Nim

import
deques, options, sequtils, tables,
chronicles,
./spec/[beaconstate, bitfield, datatypes, crypto, digest, helpers, validator],
./extras, ./beacon_chain_db, ./ssz, ./block_pool,
beacon_node_types
proc init*(T: type AttestationPool, blockPool: BlockPool): T =
T(
slots: initDeque[SlotData](),
blockPool: blockPool,
unresolved: initTable[Eth2Digest, UnresolvedAttestation](),
latestAttestations: initTable[ValidatorPubKey, BlockRef]()
)
proc combine*(tgt: var Attestation, src: Attestation, flags: UpdateFlags) =
## Combine the signature and participation bitfield, with the assumption that
## the same data is being signed - if the signatures overlap, they are not
## combined.
doAssert tgt.data == src.data
# In a BLS aggregate signature, one needs to count how many times a
# particular public key has been added - since we use a single bit per key, we
# can only it once, thus we can never combine signatures that overlap already!
if not tgt.aggregation_bits.overlaps(src.aggregation_bits):
tgt.aggregation_bits.combine(src.aggregation_bits)
if skipValidation notin flags:
tgt.signature.combine(src.signature)
proc validate(
state: BeaconState, attestation: Attestation, flags: UpdateFlags): bool =
# TODO these validations should probably be done elsewhere, and really bad
# attestations should probably cause some sort of feedback to the network
# layer so they don't spread further.. is there a sliding scale here of
# badness?
# TODO half of this stuff is from beaconstate.validateAttestation - merge?
let attestationSlot = get_attestation_data_slot(state, attestation.data)
if attestationSlot < state.finalized_epoch.compute_start_slot_of_epoch():
debug "Old attestation",
attestationSlot = humaneSlotNum(attestationSlot),
attestationEpoch = humaneEpochNum(attestationSlot.compute_epoch_of_slot),
stateSlot = humaneSlotNum(state.slot),
finalizedEpoch = humaneEpochNum(state.finalized_epoch)
return
# TODO what makes sense here? If an attestation is from the future with
# regards to the state, something is wrong - it's a bad attestation, we're
# desperatly behind or someone is sending bogus attestations...
if attestationSlot > state.slot + 64:
debug "Future attestation",
attestationSlot = humaneSlotNum(attestationSlot),
attestationEpoch = humaneEpochNum(attestationSlot.compute_epoch_of_slot),
stateSlot = humaneSlotNum(state.slot),
finalizedEpoch = humaneEpochNum(state.finalized_epoch)
return
if not allIt(attestation.custody_bits.bits, it == 0):
notice "Invalid custody bitfield for phase 0"
return false
if not anyIt(attestation.aggregation_bits.bits, it != 0):
notice "Empty aggregation bitfield"
return false
## the rest; turns into expensive NOP until then.
if skipValidation notin flags:
let
participants = get_attesting_indices_seq(
state, attestation.data, attestation.aggregation_bits)
## TODO when the custody_bits assertion-to-emptiness disappears do this
## and fix the custody_bit_0_participants check to depend on it.
# custody_bit_1_participants = {nothing, always, because assertion above}
custody_bit_1_participants: seq[ValidatorIndex] = @[]
custody_bit_0_participants = participants
group_public_key = bls_aggregate_pubkeys(
participants.mapIt(state.validators[it].pubkey))
# Verify that aggregate_signature verifies using the group pubkey.
if not bls_verify_multiple(
@[
bls_aggregate_pubkeys(mapIt(custody_bit_0_participants,
state.validators[it].pubkey)),
bls_aggregate_pubkeys(mapIt(custody_bit_1_participants,
state.validators[it].pubkey)),
],
@[
hash_tree_root(AttestationDataAndCustodyBit(
data: attestation.data, custody_bit: false)),
hash_tree_root(AttestationDataAndCustodyBit(
data: attestation.data, custody_bit: true)),
],
attestation.signature,
get_domain(state, DOMAIN_ATTESTATION,
compute_epoch_of_slot(get_attestation_data_slot(state, attestation.data))),
):
notice "Invalid signature", participants
return false
true
proc slotIndex(
pool: var AttestationPool, state: BeaconState, attestationSlot: Slot): int =
## Grow and garbage collect pool, returning the deque index of the slot
# We keep a sliding window of attestations, roughly from the last finalized
# epoch to now, because these are the attestations that may affect the voting
# outcome. Some of these attestations will already have been added to blocks,
# while others are fresh off the network.
# TODO only the latest vote of each validator counts. Can we use that somehow?
doAssert attestationSlot >= pool.startingSlot,
"""
We should have checked in validate that attestation is newer than
finalized_slot and we never prune things before that, per below condition!
""" &
", attestationSlot: " & $humaneSlotNum(attestationSlot) &
", startingSlot: " & $humaneSlotNum(pool.startingSlot)
if pool.slots.len == 0:
# Because the first attestations may arrive in any order, we'll make sure
# to start counting at the last finalized epoch start slot - anything
# earlier than that is thrown out by the above check
info "First attestation!",
attestationSlot = $humaneSlotNum(attestationSlot)
pool.startingSlot = state.finalized_epoch.compute_start_slot_of_epoch()
if pool.startingSlot + pool.slots.len.uint64 <= attestationSlot:
debug "Growing attestation pool",
attestationSlot = $humaneSlotNum(attestationSlot),
startingSlot = $humaneSlotNum(pool.startingSlot)
# Make sure there's a pool entry for every slot, even when there's a gap
while pool.startingSlot + pool.slots.len.uint64 <= attestationSlot:
pool.slots.addLast(SlotData())
if pool.startingSlot < state.finalized_epoch.compute_start_slot_of_epoch():
debug "Pruning attestation pool",
startingSlot = $humaneSlotNum(pool.startingSlot),
finalizedSlot =
$humaneSlotNum(state.finalized_epoch.compute_start_slot_of_epoch())
# TODO there should be a better way to remove a whole epoch of stuff..
while pool.startingSlot < state.finalized_epoch.compute_start_slot_of_epoch():
pool.slots.popFirst()
pool.startingSlot += 1
int(attestationSlot - pool.startingSlot)
proc updateLatestVotes(
pool: var AttestationPool, state: BeaconState, attestationSlot: Slot,
participants: seq[ValidatorIndex], blck: BlockRef) =
for validator in participants:
let
pubKey = state.validators[validator].pubkey
current = pool.latestAttestations.getOrDefault(pubKey)
if current.isNil or current.slot < attestationSlot:
pool.latestAttestations[pubKey] = blck
proc add*(pool: var AttestationPool,
state: BeaconState,
attestation: Attestation) =
# TODO should validate against the state of the block being attested to?
if not validate(state, attestation, {skipValidation}):
return
# TODO inefficient data structures..
let
attestationSlot = get_attestation_data_slot(state, attestation.data)
idx = pool.slotIndex(state, attestationSlot)
slotData = addr pool.slots[idx]
validation = Validation(
aggregation_bits: attestation.aggregation_bits,
custody_bits: attestation.custody_bits,
aggregate_signature: attestation.signature)
participants = get_attesting_indices_seq(
state, attestation.data, validation.aggregation_bits)
var found = false
for a in slotData.attestations.mitems():
if a.data == attestation.data:
for v in a.validations:
if validation.aggregation_bits.isSubsetOf(v.aggregation_bits):
# The validations in the new attestation are a subset of one of the
# attestations that we already have on file - no need to add this
# attestation to the database
# TODO what if the new attestation is useful for creating bigger
# sets by virtue of not overlapping with some other attestation
# and therefore being useful after all?
debug "Ignoring subset attestation",
existingParticipants = get_attesting_indices_seq(
state, a.data, v.aggregation_bits),
newParticipants = participants
found = true
break
if not found:
# Attestations in the pool that are a subset of the new attestation
# can now be removed per same logic as above
a.validations.keepItIf(
if it.aggregation_bits.isSubsetOf(
validation.aggregation_bits):
debug "Removing subset attestation",
existingParticipants = get_attesting_indices_seq(
state, a.data, it.aggregation_bits),
newParticipants = participants
false
else:
true)
a.validations.add(validation)
pool.updateLatestVotes(state, attestationSlot, participants, a.blck)
info "Attestation resolved",
attestationData = shortLog(attestation.data),
validations = a.validations.len()
found = true
break
if not found:
if (let blck = pool.blockPool.getOrResolve(
attestation.data.beacon_block_root); blck != nil):
slotData.attestations.add(AttestationEntry(
data: attestation.data,
blck: blck,
validations: @[validation]
))
pool.updateLatestVotes(state, attestationSlot, participants, blck)
info "Attestation resolved",
attestationData = shortLog(attestation.data),
validations = 1
else:
pool.unresolved[attestation.data.beacon_block_root] =
UnresolvedAttestation(
attestation: attestation,
)
proc getAttestationsForBlock*(
pool: AttestationPool, state: BeaconState,
newBlockSlot: Slot): seq[Attestation] =
if newBlockSlot - GENESIS_SLOT < MIN_ATTESTATION_INCLUSION_DELAY:
debug "Too early for attestations",
newBlockSlot = humaneSlotNum(newBlockSlot)
return
if pool.slots.len == 0: # startingSlot not set yet!
info "No attestations found (pool empty)",
newBlockSlot = humaneSlotNum(newBlockSlot)
return
var cache = get_empty_per_epoch_cache()
let
# TODO in theory we could include attestations from other slots also, but
# we're currently not tracking which attestations have already been included
# in blocks on the fork we're aiming for.. this is a conservative approach
# that's guaranteed to not include any duplicates, because it's the first
# time the attestations are up for inclusion!
attestationSlot = newBlockSlot - MIN_ATTESTATION_INCLUSION_DELAY
if attestationSlot < pool.startingSlot or
attestationSlot >= pool.startingSlot + pool.slots.len.uint64:
info "No attestations",
attestationSlot = humaneSlotNum(attestationSlot),
startingSlot = humaneSlotNum(pool.startingSlot),
endingSlot = humaneSlotNum(pool.startingSlot + pool.slots.len.uint64)
return
let
slotDequeIdx = int(attestationSlot - pool.startingSlot)
slotData = pool.slots[slotDequeIdx]
for a in slotData.attestations:
var
attestation = Attestation(
aggregation_bits: a.validations[0].aggregation_bits,
data: a.data,
custody_bits: a.validations[0].custody_bits,
signature: a.validations[0].aggregate_signature
)
# TODO what's going on here is that when producing a block, we need to
# include only such attestations that will not cause block validation
# to fail. How this interacts with voting and the acceptance of
# attestations into the pool in general is an open question that needs
# revisiting - for example, when attestations are added, against which
# state should they be validated, if at all?
if not process_attestation(
state, attestation, {skipValidation, nextSlot}, cache):
continue
for v in a.validations[1..^1]:
# TODO We need to select a set of attestations that maximise profit by
# adding the largest combined attestation set that we can find - this
# unfortunately looks an awful lot like
# https://en.wikipedia.org/wiki/Set_packing - here we just iterate
# and naively add as much as possible in one go, by we could also
# add the same attestation data twice, as long as there's at least
# one new attestation in there
if not attestation.aggregation_bits.overlaps(
v.aggregation_bits):
attestation.aggregation_bits.combine(
v.aggregation_bits)
attestation.custody_bits.combine(v.custody_bits)
attestation.signature.combine(v.aggregate_signature)
result.add(attestation)
if result.len >= MAX_ATTESTATIONS:
return
proc resolve*(pool: var AttestationPool, state: BeaconState) =
var done: seq[Eth2Digest]
var resolved: seq[Attestation]
for k, v in pool.unresolved.mpairs():
let attestation_slot = get_attestation_data_slot(state, v.attestation.data)
if v.tries > 8 or attestation_slot < pool.startingSlot:
done.add(k)
else:
if pool.blockPool.get(k).isSome():
resolved.add(v.attestation)
done.add(k)
else:
inc v.tries
for k in done:
pool.unresolved.del(k)
for a in resolved:
pool.add(state, a)
proc latestAttestation*(
pool: AttestationPool, pubKey: ValidatorPubKey): BlockRef =
pool.latestAttestations.getOrDefault(pubKey)