Optimise and refine SingleAttestation conversion (#6934)

Closes

- https://github.com/sigp/lighthouse/issues/6805


  - Use a new `WorkEvent::GossipAttestationToConvert` to handle the conversion from `SingleAttestation` to `Attestation` _on_ the beacon processor (prevents a Tokio thread being blocked).
- Improve the error handling for single attestations. I think previously we had no ability to reprocess single attestations for unknown blocks -- we would just error. This seemed to be the case in both gossip processing and processing of `SingleAttestation`s from the HTTP API.
- Move the `SingleAttestation -> Attestation` conversion function into `beacon_chain` so that it can return the `attestation_verification::Error` type, which has well-defined error handling and peer penalties. The now-unused variants of `types::Attestation::Error` have been removed.

consensus/types/src/attestation.rs

@@ -2,7 +2,6 @@ use crate::slot_data::SlotData;
 use crate::{test_utils::TestRandom, Hash256, Slot};
 use crate::{Checkpoint, ForkVersionDeserialize};
 use derivative::Derivative;
-use safe_arith::ArithError;
 use serde::{Deserialize, Serialize};
 use ssz_derive::{Decode, Encode};
 use ssz_types::BitVector;
@@ -12,22 +11,17 @@ use test_random_derive::TestRandom;
 use tree_hash_derive::TreeHash;
 
 use super::{
-    AggregateSignature, AttestationData, BitList, ChainSpec, CommitteeIndex, Domain, EthSpec, Fork,
-    SecretKey, Signature, SignedRoot,
+    AggregateSignature, AttestationData, BitList, ChainSpec, Domain, EthSpec, Fork, SecretKey,
+    Signature, SignedRoot,
 };
 
 #[derive(Debug, PartialEq)]
 pub enum Error {
     SszTypesError(ssz_types::Error),
     AlreadySigned(usize),
-    SubnetCountIsZero(ArithError),
     IncorrectStateVariant,
     InvalidCommitteeLength,
     InvalidCommitteeIndex,
-    AttesterNotInCommittee(u64),
-    InvalidCommittee,
-    MissingCommittee,
-    NoCommitteeForSlotAndIndex { slot: Slot, index: CommitteeIndex },
 }
 
 impl From<ssz_types::Error> for Error {
@@ -587,38 +581,6 @@ pub struct SingleAttestation {
     pub signature: AggregateSignature,
 }
 
-impl SingleAttestation {
-    pub fn to_attestation<E: EthSpec>(&self, committee: &[usize]) -> Result<Attestation<E>, Error> {
-        let aggregation_bit = committee
-            .iter()
-            .enumerate()
-            .find_map(|(i, &validator_index)| {
-                if self.attester_index as usize == validator_index {
-                    return Some(i);
-                }
-                None
-            })
-            .ok_or(Error::AttesterNotInCommittee(self.attester_index))?;
-
-        let mut committee_bits: BitVector<E::MaxCommitteesPerSlot> = BitVector::default();
-        committee_bits
-            .set(self.committee_index as usize, true)
-            .map_err(|_| Error::InvalidCommitteeIndex)?;
-
-        let mut aggregation_bits =
-            BitList::with_capacity(committee.len()).map_err(|_| Error::InvalidCommitteeLength)?;
-
-        aggregation_bits.set(aggregation_bit, true)?;
-
-        Ok(Attestation::Electra(AttestationElectra {
-            aggregation_bits,
-            committee_bits,
-            data: self.data.clone(),
-            signature: self.signature.clone(),
-        }))
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

consensus/types/src/sync_committee_contribution.rs

@@ -1,7 +1,6 @@
 use super::{AggregateSignature, EthSpec, SignedRoot};
 use crate::slot_data::SlotData;
 use crate::{test_utils::TestRandom, BitVector, Hash256, Slot, SyncCommitteeMessage};
-use safe_arith::ArithError;
 use serde::{Deserialize, Serialize};
 use ssz_derive::{Decode, Encode};
 use test_random_derive::TestRandom;
@@ -11,7 +10,6 @@ use tree_hash_derive::TreeHash;
 pub enum Error {
     SszTypesError(ssz_types::Error),
     AlreadySigned(usize),
-    SubnetCountIsZero(ArithError),
 }
 
 /// An aggregation of `SyncCommitteeMessage`s, used in creating a `SignedContributionAndProof`.