fix(validation): honor soft-fork-disabled rule 215 (hdrVotesUnknown)

[arkadianet]

Problem

The Rust mainnet node stalled at block 1802240, retrying it ~once/sec and never advancing (headers reached tip, full blocks frozen ~370–480 behind):

block apply failed height=1802240
header rule failure: epoch-start header at height 1802240 votes for
unknown parameter -4 at slot 0 (rule 215)

Root cause

Block 1802240 is a voting-epoch start (1802240 % 1024 == 0). Its header votes are fc0000 → slot 0 = -4 (MaxBlockCostDecrease). Rule 215 (hdrVotesUnknown) only accepts the Increase ids {1..8, 120} (Parameters.parametersDescs) at an epoch start, so it rejected the downward proposal.

But Scala marks rule 215 mayBeDisabled = true, and mainnet's v6.0 activation disabled it via an ErgoValidationSettingsUpdate carrying rules_to_disable = [215, 409] — so the new SubblocksPerBlock parameter (id 9, also absent from parametersDescs) and downward proposals like -4 are votable at an epoch start. Scala's ValidationState never runs a disabled rule, so the canonical chain contains this block and every other node accepted it.

The Rust node already parses and stores the activated disabled-rules set, but enforced rule 215 unconditionally at both block-validation call sites — unlike rule 409, which is correctly gated on is_rule_disabled.

Fix

• Add check_votes_known_active(header, voting_length, rule_disabled) — skips rule 215 when disabled, otherwise delegates to the unchanged check_votes_known.
• Thread votes_unknown_rule_disabled through BlockValidationContext, computed in the live path from store.validation_settings().is_rule_disabled(215).
• The raw check_votes_known rule logic is untouched — still faithful to Scala when the rule is active (existing oracle tests unaffected).

Tests

• New unit test votes_known_active_skips_when_rule_215_disabled reproduces the real block 1802240 input (votes fc0000, height 1802240): asserts it's still rejected when the rule is active (regression guard) and accepted when disabled (matches the canonical chain).
• Full suites pass: ergo-validation (280), ergo-sync (130), ergo-state (clean).

End-to-end verification

Deployed the rebuilt binary to the stuck mainnet node:

• Before: fullHeight pinned at 1802239 while headers/peers at 1802722.
• After restart: applied 1802240 and the full backlog within seconds, reached tip 1802722 (gap=0), matching the local Scala reference node. No apply failed entries after restart.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Tests

  • Updated multiple block and header validation tests to exercise the new validation flag and parity between sequential/parallel paths.

• Improvements

  • Block validation now respects a configurable gate for a specific header vote rule, allowing that rule to be treated as disabled when activated by network policy (soft-fork).

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: da7b9e9a-9ea3-4da8-bed3-af84bcbdaa4a

📥 Commits

Reviewing files that changed from the base of the PR and between 8171275 and 95fcf9c.

📒 Files selected for processing (1)

• ergo-validation/tests/full_block_validation.rs

---

📝 Walkthrough

Walkthrough

Adds a boolean flag to BlockValidationContext to gate Rule 215 (hdrVotesUnknown), uses a new check_votes_known_active helper in sequential and parallel validators, wires the flag at runtime, and updates tests to exercise the gate.

Changes

Rule 215 Soft-Fork Gating

Layer / File(s)	Summary
Validation contract and implementation ergo-validation/src/block.rs, ergo-validation/src/header.rs	BlockValidationContext gains votes_unknown_rule_disabled: bool. New check_votes_known_active(header, voting_length, rule_disabled) short-circuits when disabled; unit test verifies behavior. Sequential validate_full_block and parallel validate_full_block_parallel_impl now call check_votes_known_active.
Runtime context wiring ergo-sync/src/block_proc.rs	UTXO and Digest backend paths compute store.validation_settings().is_rule_disabled(215) and set votes_unknown_rule_disabled in BlockValidationContext.
Validation test context updates ergo-validation/tests/full_block_validation.rs	Multiple full-block validation tests now explicitly set votes_unknown_rule_disabled: false. Added a test that toggles the flag and asserts the VotesUnknown gating at full-block call sites.
State integration test context updates ergo-state/tests/cost_parity_oracle_voted_params.rs, ergo-state/tests/full_block_700k.rs, ergo-state/tests/full_block_with_state.rs	Integration tests updated to include votes_unknown_rule_disabled: false in context initialization.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

🐰 I wired a flag to hush a vote,
Rule two-one-five now takes a note.
Validators check, or skip with grace,
Tests confirm the gated place.
A tiny hop, a tidy change — onward we float.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately and specifically summarizes the main change: adding validation support for soft-fork-disabled rule 215 (hdrVotesUnknown), which directly addresses the core issue resolved by this PR.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/honor-disabled-rule-215-votes-unknown

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[coderabbitai]

🧹 Nitpick comments (1)

ergo-validation/tests/full_block_validation.rs (1)

261-271: ⚡ Quick win

Add one end-to-end votes_unknown_rule_disabled: true case in this suite.

All of the new BlockValidationContext fixtures pin the flag to false, so these full-block tests still never exercise the branch that changed. A minimal epoch-start fixture that rejects with false and passes with true would protect both validate_full_block and validate_full_block_parallel against losing the gating at the call site.

Also applies to: 322-332, 414-424, 479-500, 591-601, 646-656, 714-735, 808-829

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@ergo-validation/tests/full_block_validation.rs` around lines 261 - 271, Add
an end-to-end test variant in the full-block test suite that sets
BlockValidationContext.votes_unknown_rule_disabled = true to exercise the newly
changed branch; create a minimal epoch-start block fixture that is expected to
be rejected when the flag is false and accepted when true, then call both
validate_full_block and validate_full_block_parallel with the two contexts (one
with votes_unknown_rule_disabled = false and one with true) to assert the
reject/accept behavior. Locate and update the existing fixtures built with
BlockValidationContext (e.g., occurrences around the current block_ctx
definitions) and add the paired assertions for validate_full_block and
validate_full_block_parallel so the suite covers the gating at the call site.
Ensure similar additions are made for the other listed blocks (around lines
cited) so each test set includes the true-case variant.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@ergo-validation/tests/full_block_validation.rs`:
- Around line 261-271: Add an end-to-end test variant in the full-block test
suite that sets BlockValidationContext.votes_unknown_rule_disabled = true to
exercise the newly changed branch; create a minimal epoch-start block fixture
that is expected to be rejected when the flag is false and accepted when true,
then call both validate_full_block and validate_full_block_parallel with the two
contexts (one with votes_unknown_rule_disabled = false and one with true) to
assert the reject/accept behavior. Locate and update the existing fixtures built
with BlockValidationContext (e.g., occurrences around the current block_ctx
definitions) and add the paired assertions for validate_full_block and
validate_full_block_parallel so the suite covers the gating at the call site.
Ensure similar additions are made for the other listed blocks (around lines
cited) so each test set includes the true-case variant.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 9eccb28e-ce86-4686-be04-ac28530ad2f2

📥 Commits

Reviewing files that changed from the base of the PR and between 08ee11e and 8171275.

📒 Files selected for processing (7)

• ergo-state/tests/cost_parity_oracle_voted_params.rs
• ergo-state/tests/full_block_700k.rs
• ergo-state/tests/full_block_with_state.rs
• ergo-sync/src/block_proc.rs
• ergo-validation/src/block.rs
• ergo-validation/src/header.rs
• ergo-validation/tests/full_block_validation.rs