nimbus-eth2/beacon_chain/gossip_processing/optimistic_processor.nim

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# beacon_chain
# Copyright (c) 2019-2023 Status Research & Development GmbH
# Licensed and distributed under either of
# * MIT license (license terms in the root directory or at http://opensource.org/licenses/MIT).
# * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.
{.push raises: [].}
import
chronicles, chronos,
../spec/forks,
../beacon_clock,
./gossip_validation
from ./eth2_processor import ValidationRes
export gossip_validation
logScope:
topics = "gossip_opt"
const
# Maximum `blocks` to cache (not validated; deleted on new optimistic header)
maxBlocks = 16 # <= `GOSSIP_MAX_SIZE_BELLATRIX` (10 MB) each
# Minimum interval at which spam is logged
minLogInterval = chronos.seconds(5)
type
MsgTrustedBlockProcessor* =
proc(signedBlock: ForkedMsgTrustedSignedBeaconBlock): Future[void] {.
gcsafe, raises: [Defect].}
OptimisticProcessor* = ref object
getBeaconTime: GetBeaconTimeFn
optimisticVerifier: MsgTrustedBlockProcessor
blocks: Table[Eth2Digest, ref ForkedSignedBeaconBlock]
latestOptimisticSlot: Slot
processFut: Future[void]
logMoment: Moment
proc initOptimisticProcessor*(
getBeaconTime: GetBeaconTimeFn,
optimisticVerifier: MsgTrustedBlockProcessor): OptimisticProcessor =
OptimisticProcessor(
getBeaconTime: getBeaconTime,
optimisticVerifier: optimisticVerifier)
proc validateBeaconBlock(
self: OptimisticProcessor,
signed_beacon_block: ForkySignedBeaconBlock,
wallTime: BeaconTime): Result[void, ValidationError] =
## Minimally validate a block for potential relevance.
if not (signed_beacon_block.message.slot <=
(wallTime + MAXIMUM_GOSSIP_CLOCK_DISPARITY).slotOrZero):
return errIgnore("BeaconBlock: slot too high")
if signed_beacon_block.message.slot <= self.latestOptimisticSlot:
return errIgnore("BeaconBlock: no significant progress")
if not signed_beacon_block.message.is_execution_block():
return errIgnore("BeaconBlock: no execution block")
ok()
proc processSignedBeaconBlock*(
self: OptimisticProcessor,
signedBlock: ForkySignedBeaconBlock): ValidationRes =
let
wallTime = self.getBeaconTime()
(afterGenesis, wallSlot) = wallTime.toSlot()
logScope:
blockRoot = shortLog(signedBlock.root)
blck = shortLog(signedBlock.message)
signature = shortLog(signedBlock.signature)
wallSlot
if not afterGenesis:
notice "Optimistic block before genesis"
return errIgnore("Block before genesis")
# Potential under/overflows are fine; would just create odd metrics and logs
let delay = wallTime - signedBlock.message.slot.start_beacon_time
# Start of block processing - in reality, we have already gone through SSZ
# decoding at this stage, which may be significant
debug "Optimistic block received", delay
let v = self.validateBeaconBlock(signedBlock, wallTime)
if v.isErr:
debug "Dropping optimistic block", error = v.error
return err(v.error)
# Note that validation of blocks is delayed by ~4/3 slots because we have to
# wait for the sync committee to sign the correct block and for that signature
# to be included in the next block. Therefore, we skip block validation here
# and cache the block in memory. Because there is no validation, we have to
# mitigate against bogus blocks, mostly by bounding the caches. Assuming that
# any denial-of-service attacks eventually subside, care is taken to recover.
template logWithSpamProtection(body: untyped): untyped =
block:
let now = Moment.now()
if self.logMoment + minLogInterval <= now:
logScope: minLogInterval
body
self.logMoment = now
# Store block for later verification
if not self.blocks.hasKey(signedBlock.root):
# If `blocks` is full, we got spammed with multiple blocks for a slot,
# of the optimistic header advancements have been all withheld from us.
# Whenever the optimistic header advances, old blocks are cleared,
# so we can simply ignore additional spam blocks until that happens.
if self.blocks.len >= maxBlocks:
logWithSpamProtection:
error "`blocks` full - ignoring", maxBlocks
else:
self.blocks[signedBlock.root] =
newClone(ForkedSignedBeaconBlock.init(signedBlock))
# Block validation is delegated to the sync committee and is done with delay.
# If we forward invalid spam blocks, we may be disconnected + IP banned,
# so we avoid accepting any blocks. Since we don't meaningfully contribute
# to the blocks gossip, we may also accummulate negative peer score over time.
# However, we are actively contributing to other topics, so some of the
# negative peer score may be offset through those different topics.
# The practical impact depends on the actually deployed scoring heuristics.
trace "Optimistic block cached"
return errIgnore("Validation delegated to sync committee")
proc setOptimisticHeader*(
self: OptimisticProcessor, optimisticHeader: BeaconBlockHeader) =
# If irrelevant, skip processing
if optimisticHeader.slot <= self.latestOptimisticSlot:
return
self.latestOptimisticSlot = optimisticHeader.slot
# Delete blocks that are no longer of interest
let blockRoot = optimisticHeader.hash_tree_root()
var
rootsToDelete: seq[Eth2Digest]
signedBlock: ref ForkedMsgTrustedSignedBeaconBlock
for root, blck in self.blocks:
if root == blockRoot:
signedBlock = blck.asMsgTrusted()
if blck[].slot <= optimisticHeader.slot:
rootsToDelete.add root
for root in rootsToDelete:
self.blocks.del root
# Block must be known
if signedBlock == nil:
return
# If a block is already being processed, skip (backpressure)
if self.processFut != nil:
return
self.processFut = self.optimisticVerifier(signedBlock[])
proc handleFinishedProcess(future: pointer) =
self.processFut = nil
self.processFut.addCallback(handleFinishedProcess)