fix: require chainlock signatures only after V20 activation

[xdustinface]

Pre-V20 blocks have no chainlock signatures in MnListDiff responses, but we currently incorrectly trigger failures when they are missing below v20 activation height.

V20 activation heights (from Dash Core src/chainparams.cpp):

• Mainnet: 1,987,776
• Testnet: 905,100

Added v20_activation_height() to NetworkExt and check in apply_diff and from_diff to only require signatures for post-V20 blocks.

See DIP-0029.

Summary by CodeRabbit

• New Features
  • V20 protocol support with network-specific activation heights: mainnet (block 1,987,776), testnet (block 905,100), and immediate activation on devnet/regtest
  • Protocol-aware chainlock signature validation: signatures enforced for post-V20 blocks while maintaining backward compatibility for pre-V20 protocol versions

[coderabbitai]

📝 Walkthrough

Walkthrough

This change adds network-aware V20 activation height tracking to the masternode list module. A new v20_activation_height() method is introduced to the NetworkExt trait, returning network-specific heights. The apply_diff method is updated to accept a Network parameter and enforce chainlock signature requirements based on whether the diff height meets the V20 activation threshold.

Changes

Cohort / File(s)	Summary
Network Constants dash/src/network/constants.rs	Adds v20_activation_height() method to NetworkExt trait and implements it for Network, returning 1,987,776 for Dash, 905,100 for Testnet, and 0 for Devnet/Regtest.
Masternode List Diff Application dash/src/sml/masternode_list/apply_diff.rs, dash/src/sml/masternode_list/from_diff.rs	Threads Network parameter through diff application to enable network-based gating of chainlock signatures. Enforces signature requirements post-V20 while allowing missing signatures pre-V20. Replaces direct array indexing with safe optional retrieval (get().copied().flatten()). Adds unit tests validating both V20 phases.
Masternode List Engine dash/src/sml/masternode_list_engine/mod.rs	Updates apply_diff call site to pass self.network, enabling network context during diff application and rotation signature computation.

Sequence Diagram

sequenceDiagram
    participant Engine as MasternodeListEngine
    participant Diff as apply_diff
    participant Network as NetworkExt
    participant Sigs as Signature Validation

    Engine->>Diff: apply_diff(..., network)
    Diff->>Network: v20_activation_height()
    Network-->>Diff: activation_height
    
    alt diff_end_height >= v20_activation_height
        Diff->>Sigs: Check signatures present
        alt Signatures available
            Sigs->>Sigs: Safe retrieve via get().copied().flatten()
            Sigs-->>Diff: VerifyingChainLockSignaturesType
            Diff-->>Engine: Result(MasternodeList, signature)
        else Missing signatures
            Sigs-->>Diff: IncompleteSignatureSet error
            Diff-->>Engine: Err(IncompleteSignatureSet)
        end
    else Pre-V20 (diff_end_height < activation_height)
        Diff->>Sigs: Skip strict signature check
        Sigs->>Sigs: Use available signatures if present
        Sigs-->>Diff: Optional signature result
        Diff-->>Engine: Result(MasternodeList, optional_sig)
    end

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Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Poem

🐰 V20 heights are now aware,
Networks know when signatures care—
Pre-block days were kind and free,
Post-V20: strict as can be! ✨
Safe retrieval hops along the way,
Making chainlocks bright and gay!

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: adding network-aware V20 activation height checks to require chainlock signatures only after V20 activation, which is the core functionality across all modified files.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/pre-v20-missing-signatures

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[ZocoLini]

Not sure about having a method with hardcoded heights where v20 starts, there is no other way to know it?? the v doesn't come in the data provided by the network??

[xdustinface]

there is no other way to know it?? the v doesn't come in the data provided by the network??

Not since it's activated i think. We could probably at some point introduce a chainparams module which mirrors chainparams.cpp in core.