zebra/design/data-flow.md

• Started in ProcessNewBlock, main.cpp:4258
  • Calls CheckBlock, defined at ab2b7c0969/src/main.cpp (L3930)
    • Calls CheckBlockHeader ab2b7c0969/src/main.cpp (L3900)
      • checks that the block version is not too old
        • this requires no information
      • checks that the equihash solution is valid
        • ab2b7c0969/src/pow.cpp (L96)
        • requires no information except n, k params
      • checks that the proof of work parameters are valid
        • requires the current proof of work amount params.powLimit
    • Checks the Merkle root
    • Checks size limits
    • Checks that the first transaction is coinbase, and the rest are not
    • Calls CheckTransaction for each transaction, defined at: ab2b7c0969/src/main.cpp (L1056)
      • is coinbase
      • calls CheckTransactionWithoutProofVerification, defined at: ab2b7c0969/src/main.cpp (L1078)
        • 'Basic checks that don't require any context'
        • With verifier == false, it looks like in this flow
        • Checks a whole bunch of stuff that we check with our semantic representation into structs
          • We should double check that there are no conditions on the values and amounts that we aren't already checking
            • Check for duplicate
              • inputs
              • nullifiers (within a single transaction)
              • // Transactions containing empty vin must have either non-empty vJoinSplit or non-empty vShieldedSpend.
              • // Transactions containing empty vout must have either non-empty vJoinSplit or non-empty vShieldedOutput.
              • Moar: ab2b7c0969/src/main.cpp (L1091)
    • Sum up "LegacySigOps" for each transaction and check that it's less than some maximum
  • Acquires a lock, then calls MarkBlockAsReceived (networking?)
  • Calls AcceptBlock, defined at: ab2b7c0969/src/main.cpp (L4180)
    • Calls AcceptBlockHeader, defined at: ab2b7c0969/src/main.cpp (L4130)
      • Also calls CheckBlockHeader
      • Calls ContextualCheckBlockHeader, defined at: ab2b7c0969/src/main.cpp (L3900)
        • Does checks given a pointer to the previous block
        • Check Equihash solution is valid
          • In our code we compute the equihash solution on the block alone, we will need to also do a step to check that its block height is the appopriate N+1 re: the previous block
        • Check proof of work
        • Check timestamp against prev
        • Check future timestamp soft fork rule introduced in v2.1.1-1.
          • ab2b7c0969/src/main.cpp (L4027)
        • Check timestamp
          • ab2b7c0969/src/main.cpp (L4040)
        • Reject block.nVersion < 4 blocks
        • Don't accept any forks from the main chain prior to last checkpoint
          • We will probably get this 'more naturally' and don't need to explicitly check it like this
    • Calls CheckBlock also, w/ ProofVerifier::Disabled == true
      • ab2b7c0969/src/main.cpp (L4211)
    • Calls ContextualCheckBlock, defined at ab2b7c0969/src/main.cpp (L4065)
      • For each transaction:
        • Calls ContextualCheckTransaction, defined at ab2b7c0969/src/main.cpp (L760)
          • For Zebra, we should only be doing Transaction v4 (Sapling+) checks, because checkpointing
            • If we reach a point where we are doing contextual transaction validation for the other types, abort
          • Check that all transactions are unexpired
          • A coinbase transaction cannot have output descriptions
          • All Sapling outputs in coinbase transactions MUST have valid note commitments when recovered using a 32-byte array of zeroes as the outgoing viewing key. https://zips.z.cash/zip-0213#specification
          • Compute SigHash on data to be signed and previous data to be signed
          • Check joinsplit signature on data to be signed
            • If fail, check on previous data to be signed : ab2b7c0969/src/main.cpp (L971)
          • Check Spend/Output Descriptions
            • Check Spends: ab2b7c0969/src/main.cpp (L998)
            • Check Outputs: ab2b7c0969/src/main.cpp (L1018)
            • Check final balances: ab2b7c0969/src/main.cpp (L1036)
        • Calls IsFinalTx, defined at ab2b7c0969/src/main.cpp (L675)
          • Calls tx::IsFinal(): 6d9573c66e/src/primitives/transaction.h (L401)
      • Enforce BIP 34: ab2b7c0969/src/main.cpp (L4090)
      • If blockheight < the block just before the first subsidy halving block, dispense Founder's Reward: ab2b7c0969/src/main.cpp (L4104)
      • Everything else is state/index management after good verification
  • Calls CheckBlockIndex, defined at ab2b7c0969/src/main.cpp (L5125)
  • Calls ActivateBestChain, defined at ab2b7c0969/src/main.cpp (L3513)