Sync committee related REST API implementation. (#2856)

beacon_chain/consensus_object_pools/blockchain_dag.nim

@@ -9,7 +9,7 @@
 
 import
   std/[options, sequtils, tables, sets],
-  stew/[assign2, byteutils],
+  stew/[assign2, byteutils, results],
   metrics, snappy, chronicles,
   ../spec/[
     beaconstate, eth2_merkleization, eth2_ssz_serialization, forks, helpers,
@@ -18,7 +18,7 @@ import
   ".."/beacon_chain_db,
   "."/[block_pools_types, block_quarantine, forkedbeaconstate_dbhelpers]
 
-export block_pools_types
+export block_pools_types, results
 
 # https://github.com/ethereum/eth2.0-metrics/blob/master/metrics.md#interop-metrics
 declareGauge beacon_head_root, "Root of the head block of the beacon chain"

beacon_chain/rpc/rest_beacon_api.nim

@@ -97,6 +97,24 @@ proc toString*(kind: ValidatorFilterKind): string =
   of ValidatorFilterKind.WithdrawalDone:
     "withdrawal_done"
 
+func syncCommitteeParticipants*(forkedState: ForkedHashedBeaconState,
+  epoch: Epoch): Result[seq[ValidatorPubKey], cstring] =
+  case forkedState.beaconStateFork
+  of BeaconStateFork.forkPhase0:
+    err("State's fork do not support sync committees")
+  of BeaconStateFork.forkAltair:
+    let
+      headSlot = forkedState.hbsAltair.data.slot
+      epochPeriod = syncCommitteePeriod(epoch.compute_start_slot_at_epoch())
+      currentPeriod = syncCommitteePeriod(headSlot)
+      nextPeriod = currentPeriod + 1'u64
+    if epochPeriod == currentPeriod:
+      ok(@(forkedState.hbsAltair.data.current_sync_committee.pubkeys.data))
+    elif epochPeriod == nextPeriod:
+      ok(@(forkedState.hbsAltair.data.next_sync_committee.pubkeys.data))
+    else:
+      err("Epoch is outside the sync committee period of the state")
+
 proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
   # https://ethereum.github.io/beacon-APIs/#/Beacon/getGenesis
   router.api(MethodGet, "/api/eth/v1/beacon/genesis") do () -> RestApiResponse:
@@ -468,7 +486,7 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
         none[Slot]()
     node.withStateForBlockSlot(bslot):
       proc getCommittee(slot: Slot,
-                       index: CommitteeIndex): RestBeaconStatesCommittees =
+                        index: CommitteeIndex): RestBeaconStatesCommittees =
         let validators = get_beacon_committee(stateData.data, slot, index,
                                               cache).mapIt(it)
         RestBeaconStatesCommittees(index: index, slot: slot,
@@ -504,6 +522,85 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
 
     return RestApiResponse.jsonError(Http500, InternalServerError)
 
+  # https://ethereum.github.io/beacon-APIs/#/Beacon/getEpochSyncCommittees
+  router.api(MethodGet,
+             "/api/eth/v1/beacon/states/{state_id}/sync_committees") do (
+    state_id: StateIdent, epoch: Option[Epoch]) -> RestApiResponse:
+    let bslot =
+      block:
+        if state_id.isErr():
+          return RestApiResponse.jsonError(Http400, InvalidStateIdValueError,
+                                           $state_id.error())
+        let bres = node.getBlockSlot(state_id.get())
+        if bres.isErr():
+          return RestApiResponse.jsonError(Http404, StateNotFoundError,
+                                           $bres.error())
+        bres.get()
+
+    let qepoch =
+      if epoch.isSome():
+        let repoch = epoch.get()
+        if repoch.isErr():
+          return RestApiResponse.jsonError(Http400, InvalidEpochValueError,
+                                           $repoch.error())
+        let res = repoch.get()
+        if res > MaxEpoch:
+          return RestApiResponse.jsonError(Http400, EpochOverflowValueError)
+        if res < node.dag.cfg.ALTAIR_FORK_EPOCH:
+          return RestApiResponse.jsonError(Http400,
+                                           EpochFromTheIncorrectForkError)
+        res
+      else:
+        # If ``epoch`` not present then the sync committees for the epoch of
+        # the state will be obtained.
+        bslot.slot.epoch()
+
+    node.withStateForBlockSlot(bslot):
+      let keys =
+        block:
+          let res = syncCommitteeParticipants(stateData().data, qepoch)
+          if res.isErr():
+            return RestApiResponse.jsonError(Http400,
+                                             $res.error())
+          let kres = res.get()
+          if len(kres) == 0:
+            return RestApiResponse.jsonError(Http500, InternalServerError,
+                                 "List of sync committee participants is empty")
+          kres
+
+      let indices =
+        block:
+          var res: seq[ValidatorIndex]
+          let keyset = keys.toHashSet()
+          for index, validator in getStateField(stateData.data,
+                                                validators).pairs():
+            if validator.pubkey in keyset:
+              res.add(ValidatorIndex(uint64(index)))
+          res
+
+      if len(indices) != len(keys):
+        return RestApiResponse.jsonError(Http500, InternalServerError,
+                                         "Could not get validator indices")
+      let aggregates =
+        block:
+          var
+            res: seq[seq[ValidatorIndex]]
+            offset = 0
+          while true:
+            let length = min(SYNC_SUBCOMMITTEE_SIZE, len(indices) - offset)
+            if length == 0:
+              break
+            res.add(@(indices.toOpenArray(offset, offset + length - 1)))
+            offset.inc(length)
+          res
+
+      return RestApiResponse.jsonResponse(GetEpochSyncCommitteesResponse(
+        data: RestEpochSyncCommittee(validators: indices,
+                                     validator_aggregates: aggregates)
+      ))
+
+    return RestApiResponse.jsonError(Http400, "Could not get requested state")
+
   # https://ethereum.github.io/beacon-APIs/#/Beacon/getBlockHeaders
   router.api(MethodGet, "/api/eth/v1/beacon/headers") do (
     slot: Option[Slot], parent_root: Option[Eth2Digest]) -> RestApiResponse:
@@ -893,6 +990,37 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
                                        $res.error())
     return RestApiResponse.jsonMsgResponse(ProposerSlashingValidationSuccess)
 
+  # https://ethereum.github.io/beacon-APIs/#/Beacon/submitPoolSyncCommitteeSignatures
+  router.api(MethodPost, "/api/eth/v1/beacon/pool/sync_committees") do (
+    contentBody: Option[ContentBody]) -> RestApiResponse:
+    let messages =
+      block:
+        if contentBody.isNone():
+          return RestApiResponse.jsonError(Http400, EmptyRequestBodyError)
+        let dres = decodeBody(seq[SyncCommitteeMessage], contentBody.get())
+        if dres.isErr():
+          return RestApiResponse.jsonError(Http400,
+                                      InvalidSyncCommitteeSignatureMessageError)
+        dres.get()
+
+    let results = await node.sendSyncCommitteeMessages(messages)
+
+    let failures =
+      block:
+        var res: seq[RestAttestationsFailure]
+        for index, item in results.pairs():
+          if item.isErr():
+            res.add(RestAttestationsFailure(index: uint64(index),
+                                            message: $item.error()))
+        res
+    if len(failures) > 0:
+      return RestApiResponse.jsonErrorList(Http400,
+                                           SyncCommitteeMessageValidationError,
+                                           failures)
+    else:
+      return RestApiResponse.jsonMsgResponse(
+        SyncCommitteeMessageValidationSuccess)
+
   # https://ethereum.github.io/beacon-APIs/#/Beacon/getPoolVoluntaryExits
   router.api(MethodGet, "/api/eth/v1/beacon/pool/voluntary_exits") do (
     ) -> RestApiResponse:
@@ -965,6 +1093,11 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
     "/eth/v1/beacon/states/{state_id}/committees",
     "/api/eth/v1/beacon/states/{state_id}/committees"
   )
+  router.redirect(
+    MethodGet,
+    "/eth/v1/beacon/states/{state_id}/sync_committees",
+    "/api/eth/v1/beacon/states/{state_id}/sync_committees"
+  )
   router.redirect(
     MethodGet,
     "/eth/v1/beacon/headers",
@@ -1030,6 +1163,11 @@ proc installBeaconApiHandlers*(router: var RestRouter, node: BeaconNode) =
     "/eth/v1/beacon/pool/proposer_slashings",
     "/api/eth/v1/beacon/pool/proposer_slashings"
   )
+  router.redirect(
+    MethodPost,
+    "/eth/v1/beacon/pool/sync_committees",
+    "/api/eth/v1/beacon/pool/sync_committees"
+  )
   router.redirect(
     MethodPost,
     "/eth/v1/beacon/pool/voluntary_exits",

beacon_chain/rpc/rest_utils.nim

@@ -58,7 +58,9 @@ const
   AggregateAndProofValidationSuccess* =
     "Aggregate and proof object(s) was broadcasted"
   BeaconCommitteeSubscriptionSuccess* =
-    "Beacon node processed committee subscription request"
+    "Beacon node processed committee subscription request(s)"
+  SyncCommitteeSubscriptionSuccess* =
+    "Beacon node processed sync committee subscription request(s)"
   InvalidParentRootValueError* =
     "Invalid parent root value"
   MissingSlotValueError* =
@@ -119,6 +121,10 @@ const
     "Requested slot not in next wall-slot epoch"
   SlotFromThePastError* =
     "Requested slot from the past"
+  SlotFromTheIncorrectForkError* =
+    "Requested slot is from incorrect fork"
+  EpochFromTheIncorrectForkError* =
+    "Requested epoch is from incorrect fork"
   ProposerNotFoundError* =
     "Could not find proposer for the head and slot"
   NoHeadForSlotError* =
@@ -139,6 +145,32 @@ const
     "Could not find out accepted content type"
   InvalidAcceptError* =
     "Incorrect accept response type"
+  MissingSubCommitteeIndexValueError* =
+    "Missing `subcommittee_index` value"
+  InvalidSubCommitteeIndexValueError* =
+    "Invalid `subcommittee_index` value"
+  MissingBeaconBlockRootValueError* =
+    "Missing `beacon_block_root` value"
+  InvalidBeaconBlockRootValueError* =
+    "Invalid `beacon_block_root` value"
+  EpochOutsideSyncCommitteePeriodError* =
+    "Epoch is outside the sync committee period of the state"
+  InvalidSyncCommitteeSignatureMessageError* =
+    "Unable to decode sync committee message(s)"
+  InvalidSyncCommitteeSubscriptionRequestError* =
+    "Unable to decode sync committee subscription request(s)"
+  InvalidContributionAndProofMessageError* =
+    "Unable to decode contribute and proof message(s)"
+  SyncCommitteeMessageValidationError* =
+    "Some errors happened while validating sync committee message(s)"
+  SyncCommitteeMessageValidationSuccess* =
+    "Sync committee message(s) was broadcasted"
+  ContributionAndProofValidationError* =
+    "Some errors happened while validating contribution and proof(s)"
+  ContributionAndProofValidationSuccess* =
+    "Contribution and proof(s) was broadcasted"
+  ProduceContributionError* =
+    "Unable to produce contribution using the passed parameters"
   InternalServerError* =
     "Internal server error"
   NoImplementationError* =

beacon_chain/rpc/rest_validator_api.nim

@@ -3,19 +3,18 @@
 #   * 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
-  std/[typetraits, strutils],
-  stew/[results, base10],
-  chronicles,
-  json_serialization, json_serialization/std/[options, net],
-  nimcrypto/utils as ncrutils,
-  ".."/[beacon_chain_db, beacon_node_common],
-  ../networking/eth2_network,
-  ../consensus_object_pools/[blockchain_dag, spec_cache, attestation_pool],
-  ../validators/validator_duties,
-  ../spec/[forks, network],
-  ../spec/datatypes/[phase0, altair],
-  ./rest_utils
+import std/[typetraits, strutils]
+import stew/[results, base10], chronicles, json_serialization,
+       json_serialization/std/[options, net],
+       nimcrypto/utils as ncrutils
+import ".."/[beacon_chain_db, beacon_node_common],
+       ".."/networking/eth2_network,
+       ".."/consensus_object_pools/[blockchain_dag, spec_cache,
+                                    attestation_pool, sync_committee_msg_pool],
+       ".."/validators/validator_duties,
+       ".."/spec/[forks, network],
+       ".."/spec/datatypes/[phase0, altair],
+       "."/rest_utils
 
 logScope: topics = "rest_validatorapi"
 
@@ -383,7 +382,7 @@ proc installValidatorApiHandlers*(router: var RestRouter, node: BeaconNode) =
         block:
           let idx = request.validator_index
           if uint64(idx) >=
-                           lenu64(getStateField(node.dag.headState.data, validators)):
+                     lenu64(getStateField(node.dag.headState.data, validators)):
             return RestApiResponse.jsonError(Http400,
                                              InvalidValidatorIndexValueError)
           getStateField(node.dag.headState.data, validators)[idx].pubkey
@@ -410,6 +409,146 @@ proc installValidatorApiHandlers*(router: var RestRouter, node: BeaconNode) =
     warn "Beacon committee subscription request served, but not implemented"
     return RestApiResponse.jsonMsgResponse(BeaconCommitteeSubscriptionSuccess)
 
+  # https://ethereum.github.io/beacon-APIs/#/Validator/prepareSyncCommitteeSubnets
+  router.api(MethodPost,
+             "/api/eth/v1/validator/sync_committee_subscriptions") do (
+    contentBody: Option[ContentBody]) -> RestApiResponse:
+    let subscriptions =
+      block:
+        if contentBody.isNone():
+          return RestApiResponse.jsonError(Http400, EmptyRequestBodyError)
+        let dres = decodeBody(seq[RestSyncCommitteeSubscription],
+                              contentBody.get())
+        if dres.isErr():
+          return RestApiResponse.jsonError(Http400,
+                                   InvalidSyncCommitteeSubscriptionRequestError)
+        let subs = dres.get()
+        for item in subs:
+          if item.until_epoch > MaxEpoch:
+            return RestApiResponse.jsonError(Http400, EpochOverflowValueError)
+          if item.until_epoch < node.dag.cfg.ALTAIR_FORK_EPOCH:
+            return RestApiResponse.jsonError(Http400,
+                                             EpochFromTheIncorrectForkError)
+          if uint64(item.validator_index) >=
+             lenu64(getStateField(node.dag.headState.data, validators)):
+            return RestApiResponse.jsonError(Http400,
+                                             InvalidValidatorIndexValueError)
+        subs
+
+    warn "Sync committee subscription request served, but not implemented"
+    return RestApiResponse.jsonMsgResponse(SyncCommitteeSubscriptionSuccess)
+
+  # https://ethereum.github.io/beacon-APIs/#/Validator/produceSyncCommitteeContribution
+  router.api(MethodGet,
+             "/api/eth/v1/validator/sync_committee_contribution") do (
+    slot: Option[Slot], subcommittee_index: Option[uint64],
+    beacon_block_root: Option[Eth2Digest]) -> RestApiResponse:
+    # We doing this check to avoid any confusion in future.
+    static: doAssert(SYNC_COMMITTEE_SUBNET_COUNT <= high(uint8))
+    let qslot =
+      if slot.isNone():
+        return RestApiResponse.jsonError(Http400, MissingSlotValueError)
+      else:
+        let res = slot.get()
+        if res.isErr():
+          return RestApiResponse.jsonError(Http400, InvalidSlotValueError,
+                                           $res.error())
+        let rslot = res.get()
+        if epoch(rslot) < node.dag.cfg.ALTAIR_FORK_EPOCH:
+          return RestApiResponse.jsonError(Http400,
+                                           SlotFromTheIncorrectForkError)
+        rslot
+    let qindex =
+      if subcommittee_index.isNone():
+        return RestApiResponse.jsonError(Http400,
+                                         MissingSubCommitteeIndexValueError)
+      else:
+        let res = subcommittee_index.get()
+        if res.isErr():
+          return RestApiResponse.jsonError(Http400,
+                                           InvalidSubCommitteeIndexValueError,
+                                           $res.error())
+        let value = res.get()
+        if value >= SYNC_COMMITTEE_SUBNET_COUNT:
+          return RestApiResponse.jsonError(Http400,
+                                           InvalidSubCommitteeIndexValueError,
+                                           "subcommittee_index exceeds " &
+                                           "maximum allowed value")
+        value
+    let qroot =
+      if beacon_block_root.isNone():
+        return RestApiResponse.jsonError(Http400,
+                                         MissingBeaconBlockRootValueError)
+      else:
+        let res = beacon_block_root.get()
+        if res.isErr():
+          return RestApiResponse.jsonError(Http400,
+                                           InvalidBeaconBlockRootValueError,
+                                           $res.error())
+        res.get()
+
+    # Check if node is fully synced.
+    let sres = node.getCurrentHead(qslot)
+    if sres.isErr():
+      return RestApiResponse.jsonError(Http503, BeaconNodeInSyncError)
+
+    var contribution = SyncCommitteeContribution()
+    let res = node.syncCommitteeMsgPool[].produceContribution(
+      qslot, qroot, SyncCommitteeIndex(qindex), contribution)
+    if not(res):
+      return RestApiResponse.jsonError(Http400, ProduceContributionError)
+    return RestApiResponse.jsonResponse(contribution)
+
+  # https://ethereum.github.io/beacon-APIs/#/Validator/publishContributionAndProofs
+  router.api(MethodPost,
+             "/api/eth/v1/validator/contribution_and_proofs") do (
+    contentBody: Option[ContentBody]) -> RestApiResponse:
+    let proofs =
+      block:
+        if contentBody.isNone():
+          return RestApiResponse.jsonError(Http400, EmptyRequestBodyError)
+        let dres = decodeBody(seq[SignedContributionAndProof],
+                              contentBody.get())
+        if dres.isErr():
+          return RestApiResponse.jsonError(Http400,
+                                        InvalidContributionAndProofMessageError)
+        dres.get()
+
+    let pending =
+      block:
+        var res: seq[Future[SendResult]]
+        for proof in proofs:
+          res.add(node.sendSyncCommitteeContribution(proof, true))
+        res
+
+    let failures =
+      block:
+        var res: seq[RestAttestationsFailure]
+        await allFutures(pending)
+        for index, future in pending.pairs():
+          if future.done():
+            let fres = future.read()
+            if fres.isErr():
+              let failure = RestAttestationsFailure(index: uint64(index),
+                                                    message: $fres.error())
+              res.add(failure)
+          elif future.failed() or future.cancelled():
+            # This is unexpected failure, so we log the error message.
+            let exc = future.readError()
+            let failure = RestAttestationsFailure(index: uint64(index),
+                                                  message: $exc.msg)
+            res.add(failure)
+        res
+
+    if len(failures) > 0:
+      return RestApiResponse.jsonErrorList(Http400,
+                                           ContributionAndProofValidationError,
+                                           failures)
+    else:
+      return RestApiResponse.jsonMsgResponse(
+        ContributionAndProofValidationSuccess
+      )
+
   router.redirect(
     MethodPost,
     "/eth/v1/validator/duties/attester/{epoch}",
@@ -450,3 +589,18 @@ proc installValidatorApiHandlers*(router: var RestRouter, node: BeaconNode) =
     "/eth/v1/validator/beacon_committee_subscriptions",
     "/api/eth/v1/validator/beacon_committee_subscriptions"
   )
+  router.redirect(
+    MethodPost,
+    "/eth/v1/validator/sync_committee_subscriptions",
+    "/api/eth/v1/validator/sync_committee_subscriptions"
+  )
+  router.redirect(
+    MethodGet,
+    "/eth/v1/validator/sync_committee_contribution",
+    "/api/eth/v1/validator/sync_committee_contribution"
+  )
+  router.redirect(
+    MethodPost,
+    "/eth/v1/validator/contribution_and_proofs",
+    "/api/eth/v1/validator/contribution_and_proofs"
+  )

beacon_chain/spec/eth2_apis/eth2_rest_serialization.nim

@@ -803,6 +803,22 @@ template toSszType*(v: BeaconStateFork): auto =
   of BeaconStateFork.forkPhase0: Phase0Version
   of BeaconStateFork.forkAltair: AltairVersion
 
+# SyncCommitteeIndex
+proc writeValue*(writer: var JsonWriter[RestJson],
+                 value: SyncCommitteeIndex) {.
+     raises: [IOError, Defect].} =
+  writeValue(writer, Base10.toString(uint8(value)))
+
+proc readValue*(reader: var JsonReader[RestJson],
+                value: var SyncCommitteeIndex) {.
+     raises: [IOError, SerializationError, Defect].} =
+  let res = Base10.decode(uint8, reader.readValue(string))
+  if res.isOk():
+    # TODO (cheatfate): Here should be present check for maximum value.
+    value = SyncCommitteeIndex(res.get())
+  else:
+    reader.raiseUnexpectedValue($res.error())
+
 proc parseRoot(value: string): Result[Eth2Digest, cstring] =
   try:
     ok(Eth2Digest(data: hexToByteArray[32](value)))
@@ -1030,6 +1046,10 @@ proc decodeString*(t: typedesc[Epoch], value: string): Result[Epoch, cstring] =
   let res = ? Base10.decode(uint64, value)
   ok(Epoch(res))
 
+proc decodeString*(t: typedesc[uint64],
+                   value: string): Result[uint64, cstring] =
+  Base10.decode(uint64, value)
+
 proc decodeString*(t: typedesc[StateIdent],
                    value: string): Result[StateIdent, cstring] =
   if len(value) > 2:

beacon_chain/spec/eth2_apis/rest_types.nim

@@ -108,6 +108,11 @@ type
     slot*: Slot
     is_aggregator*: bool
 
+  RestSyncCommitteeSubscription* = object
+    validator_index*: ValidatorIndex
+    sync_committee_indices*: seq[SyncCommitteeIndex]
+    until_epoch*: Epoch
+
   RestBeaconStatesFinalityCheckpoints* = object
     previous_justified*: Checkpoint
     current_justified*: Checkpoint
@@ -261,6 +266,10 @@ type
     slot*: Slot
     blck* {.serializedFieldName: "block".}: Eth2Digest
     
+  RestEpochSyncCommittee* = object
+    validators*: seq[ValidatorIndex]
+    validator_aggregates*: seq[seq[ValidatorIndex]]
+
   DataEnclosedObject*[T] = object
     data*: T
 
@@ -305,6 +314,7 @@ type
   GetStateValidatorsResponse* = DataEnclosedObject[seq[RestValidator]]
   GetSyncingStatusResponse* = DataEnclosedObject[RestSyncInfo]
   GetVersionResponse* = DataEnclosedObject[RestNodeVersion]
+  GetEpochSyncCommitteesResponse* = DataEnclosedObject[RestEpochSyncCommittee]
   ProduceAttestationDataResponse* = DataEnclosedObject[AttestationData]
   ProduceBlockResponse* = DataEnclosedObject[phase0.BeaconBlock]
   ProduceBlockResponseV2* = ForkedBeaconBlock

beacon_chain/validators/validator_duties.nim

@@ -200,28 +200,118 @@ proc sendAttestation*(
 
 proc sendSyncCommitteeMessage*(
     node: BeaconNode, msg: SyncCommitteeMessage,
-    committeeIdx: SyncCommitteeIndex, checkSignature: bool): Future[bool] {.async.} =
+    committeeIdx: SyncCommitteeIndex,
+    checkSignature: bool): Future[SendResult] {.async.} =
   # Validate sync committee message before sending it via gossip
   # validation will also register the message with the sync committee
   # message pool. Notably, although libp2p calls the data handler for
   # any subscription on the subnet topic, it does not perform validation.
-  let ok = node.processor.syncCommitteeMsgValidator(
-    msg, committeeIdx, checkSignature)
-
-  return case ok
+  let res = node.processor.syncCommitteeMsgValidator(msg, committeeIdx,
+                                                     checkSignature)
+  return
+    case res
     of ValidationResult.Accept:
       node.network.broadcastSyncCommitteeMessage(msg, committeeIdx)
       beacon_sync_committee_messages_sent.inc()
-      true
+      SendResult.ok()
     else:
-      notice "Produced sync committee message failed validation",
-              msg, result = $ok
-      false
+      notice "Sync committee message failed validation",
+             msg, result = $res
+      SendResult.err("Sync committee message failed validation")
+
+proc sendSyncCommitteeMessages*(node: BeaconNode,
+                                msgs: seq[SyncCommitteeMessage]
+                               ): Future[seq[SendResult]] {.async.} =
+  let validators = getStateField(node.dag.headState.data, validators)
+  var statuses = newSeq[Option[SendResult]](len(msgs))
+
+  let ranges =
+    block:
+      let
+        headSlot = getStateField(node.dag.headState.data, slot)
+        headCommitteePeriod = syncCommitteePeriod(headSlot)
+        currentStart = syncCommitteePeriodStartSlot(headCommitteePeriod)
+        currentFinish = currentStart + SLOTS_PER_SYNC_COMMITTEE_PERIOD
+        nextStart = currentFinish
+        nextFinish = nextStart + SLOTS_PER_SYNC_COMMITTEE_PERIOD
+      (curStart: Slot(currentStart), curFinish: Slot(currentFinish),
+        nxtStart: Slot(nextStart), nxtFinish: Slot(nextFinish))
+
+  let (keysCur, keysNxt) =
+    block:
+      var resCur: Table[ValidatorPubKey, int]
+      var resNxt: Table[ValidatorPubKey, int]
+      for index, msg in msgs.pairs():
+        if msg.validator_index < lenu64(validators):
+          if (msg.slot >= ranges.curStart) and (msg.slot < ranges.curFinish):
+            resCur[validators[msg.validator_index].pubkey] = index
+          elif (msg.slot >= ranges.nxtStart) and (msg.slot < ranges.nxtFinish):
+            resNxt[validators[msg.validator_index].pubkey] = index
+          else:
+            statuses[index] =
+              some(SendResult.err("Message's slot out of state's head range"))
+        else:
+          statuses[index] = some(SendResult.err("Incorrect validator's index"))
+      if (len(resCur) == 0) and (len(resNxt) == 0):
+        return statuses.mapIt(it.get())
+      (resCur, resNxt)
+
+  template curParticipants(): untyped =
+    node.dag.headState.data.hbsAltair.data.current_sync_committee.pubkeys.data
+  template nxtParticipants(): untyped =
+    node.dag.headState.data.hbsAltair.data.next_sync_committee.pubkeys.data
+
+  let (pending, indices) =
+    block:
+      var resFutures: seq[Future[SendResult]]
+      var resIndices: seq[int]
+      for committeeIdx in allSyncCommittees():
+        for valKey in syncSubcommittee(curParticipants(), committeeIdx):
+          let index = keysCur.getOrDefault(valKey, -1)
+          if index >= 0:
+            resIndices.add(index)
+            resFutures.add(node.sendSyncCommitteeMessage(msgs[index],
+                                                         committeeIdx, true))
+      for committeeIdx in allSyncCommittees():
+        for valKey in syncSubcommittee(nxtParticipants(), committeeIdx):
+          let index = keysNxt.getOrDefault(valKey, -1)
+          if index >= 0:
+            resIndices.add(index)
+            resFutures.add(node.sendSyncCommitteeMessage(msgs[index],
+                                                         committeeIdx, true))
+      (resFutures, resIndices)
+
+  await allFutures(pending)
+
+  for index, future in pending.pairs():
+    if future.done():
+      let fres = future.read()
+      if fres.isErr():
+        statuses[indices[index]] = some(SendResult.err(fres.error()))
+      else:
+        statuses[indices[index]] = some(SendResult.ok())
+    elif future.failed() or future.cancelled():
+      let exc = future.readError()
+      debug "Unexpected failure while sending committee message",
+        message = msgs[indices[index]], error = $exc.msg
+      statuses[indices[index]] = some(SendResult.err(
+        "Unexpected failure while sending committee message"))
+
+  let results =
+    block:
+      var res: seq[SendResult]
+      for item in statuses:
+        if item.isSome():
+          res.add(item.get())
+        else:
+          res.add(SendResult.err("Message validator not in sync committee"))
+      res
+  return results
 
 proc sendSyncCommitteeContribution*(
     node: BeaconNode,
     msg: SignedContributionAndProof,
-    checkSignature: bool): Future[bool] {.async.} =
+    checkSignature: bool): Future[SendResult] {.async.} =
   let ok = node.processor.syncCommitteeContributionValidator(
     msg, checkSignature)
 
@@ -229,11 +319,11 @@ proc sendSyncCommitteeContribution*(
     of ValidationResult.Accept:
       node.network.broadcastSignedContributionAndProof(msg)
       beacon_sync_committee_contributions_sent.inc()
-      true
+      SendResult.ok()
     else:
-      notice "Produced sync committee contribution failed validation",
+      notice "Sync committee contribution failed validation",
               msg, result = $ok
-      false
+      SendResult.err("Sync committee contribution failed validation")
 
 proc createAndSendAttestation(node: BeaconNode,
                               fork: Fork,
@@ -598,9 +688,10 @@ proc createAndSendSyncCommitteeMessage(node: BeaconNode,
       msg = await signSyncCommitteeMessage(validator, slot, fork,
                                            genesisValidatorsRoot, head.root)
 
-    let ok = await node.sendSyncCommitteeMessage(
+    let res = await node.sendSyncCommitteeMessage(
       msg, committeeIdx, checkSignature = false)
-    if not ok: # Logged in sendSyncCommitteeMessage
+    if res.isErr():
+      # Logged in sendSyncCommitteeMessage
       return
 
     if node.config.dumpEnabled:
@@ -635,7 +726,7 @@ proc handleSyncCommitteeMessages(node: BeaconNode, head: BlockRef, slot: Slot) =
   for committeeIdx in allSyncCommittees():
     for valKey in syncSubcommittee(syncCommittee, committeeIdx):
       let validator = node.getAttachedValidator(valKey)
-      if validator == nil or not validator.index.isSome():
+      if isNil(validator) or validator.index.isNone():
         continue
       asyncSpawn createAndSendSyncCommitteeMessage(node, slot, validator,
                                                    committeeIdx, head)