*: sync contributions per subcommittee

[KaloyanTanev]

Fix distributed validators only aggregating one sync committee subcommittee per slot. A validator in multiple subcommittees produces a distinct selection and contribution-and-proof per subcommittee, but these were keyed by (duty, pubkey) alone and collided, dropping all but one.

Add core.SubcommitteeIndex to the partial-signature key (ParSigDB, AggSigDB, ValidatorAPI) and make the DutySyncContribution unsigned data a plural SyncContributions, one per subcommittee.

Since older nodes can't decode the plural form, it is version-gated via info-sync: the fetcher emits it only once a threshold of peers advertise >= v1.11, else falls back to the single-contribution wire format.

category: bug
ticket: none

[Copilot]

Pull request overview

Fixes a sync-committee aggregation correctness issue where validators that are aggregators for multiple sync subcommittees in the same slot would have their data collide when keyed only by (duty, pubkey), causing all but one subcommittee’s selection/contribution to be dropped. The PR extends the partial/aggregated signature keying to include a core.SubcommitteeIndex for sync-committee aggregator duties, and updates sync-contribution unsigned data to support multiple contributions per validator (version-gated for backwards compatibility).

Changes:

• Add core.SubcommitteeIndex and thread it through ValidatorAPI, Fetcher, ParSigDB, AggSigDB, and wiring/tracing so sync-committee aggregator signatures are disambiguated per subcommittee.
• Change DutySyncContribution unsigned data to support plural core.SyncContributions (JSON array), while remaining tolerant of the legacy single core.SyncContribution wire form.
• Add info-sync based gating (>= v1.11) to only emit the plural encoding once a threshold of peers supports it; expand tests to cover both encodings and multi-subcommittee behavior.

Reviewed changes

Copilot reviewed 23 out of 23 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
app/app.go	Wires infosync into fetcher to gate plural SyncContributions encoding when available.
core/aggsigdb/memory.go	Keys aggregated signatures by (duty, pubkey, subcommIdx) and updates Await API accordingly.
core/aggsigdb/memory_internal_test.go	Updates AggSigDB tests for the new Await signature (subcommittee index).
core/aggsigdb/memory_test.go	Updates AggSigDB tests for the new Await signature (subcommittee index).
core/aggsigdb/memory_v2.go	Updates MemDBV2 to store/await aggregated signatures with subcommittee keying.
core/aggsigdb/memory_v2_internal_test.go	Updates MemDBV2 internal tests for the new Await signature (subcommittee index).
core/dutydb/memory.go	Stores plural/single sync contributions, persisting each contribution entry keyed by slot/subcommittee/root.
core/dutydb/memory_test.go	Updates sync contribution DutyDB tests for the plural unsigned-data form and revised error text.
core/fetcher/fetcher.go	Fetches multiple per-subcommittee contributions per validator, with version-gated plural vs legacy single encoding.
core/fetcher/fetcher_test.go	Expands fetcher tests to cover plural encoding and a backwards-compatible single-contribution mode.
core/infosync/infosync.go	Adds quorum-based gating signal (SyncContributionsSupported) driven by cluster-agreed versions.
core/infosync/infosync_internal_test.go	Adds tests for version gating logic and slot-based enabled/disabled transitions.
core/interfaces.go	Extends AggSigDB / Fetcher / ValidatorAPI interfaces to include SubcommitteeIndex for sync duties.
core/parsigdb/memory.go	Keys partial signatures by (duty, pubkey, subcommIdx) using signed payload to derive the subcommittee index.
core/proto_test.go	Updates proto round-trip tests and adds compatibility coverage for plural vs single sync contribution forms.
core/signeddata.go	Adds SyncSubcommitteeIndex helper and IsSyncSubcommitteeDuty support to derive subcommittee keying from signed payloads.
core/signeddata_test.go	Adds unit test coverage for SyncSubcommitteeIndex.
core/ssz_test.go	Updates unsigned proto marshalling test to use SyncContributions for DutySyncContribution.
core/tracing.go	Threads SubcommitteeIndex through tracing wrapper for AggSigDB Await.
core/types.go	Introduces SubcommitteeIndex type and IsSyncSubcommitteeDuty helper.
core/unsigneddata.go	Introduces SyncContributions unsigned type and makes DutySyncContribution decoder accept plural or legacy single forms.
core/validatorapi/validatorapi.go	Groups sync selections/contributions by (slot, subcommittee) to avoid pubkey collisions and queries AggSigDB with subcommittee index.
core/validatorapi/validatorapi_test.go	Updates validator API tests to validate per-subcommittee behavior and new AggSigDB await signature.

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[codecov]

Codecov Report

❌ Patch coverage is 67.56757% with 72 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.55%. Comparing base (2eb6798) to head (65bc87c).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
core/fetcher/fetcher.go	68.60%	13 Missing and 14 partials ⚠️
core/unsigneddata.go	38.46%	13 Missing and 3 partials ⚠️
core/infosync/infosync.go	69.69%	7 Missing and 3 partials ⚠️
app/app.go	0.00%	7 Missing ⚠️
core/aggsigdb/memory.go	80.00%	1 Missing and 1 partial ⚠️
core/aggsigdb/memory_v2.go	77.77%	1 Missing and 1 partial ⚠️
core/dutydb/memory.go	81.81%	2 Missing ⚠️
core/parsigdb/memory.go	50.00%	1 Missing and 1 partial ⚠️
core/signeddata.go	80.00%	2 Missing ⚠️
core/tracing.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4602      +/-   ##
==========================================
- Coverage   57.58%   57.55%   -0.04%     
==========================================
  Files         246      246              
  Lines       33675    33814     +139     
==========================================
+ Hits        19392    19461      +69     
- Misses      11845    11901      +56     
- Partials     2438     2452      +14     

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[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud