Enforce nLockTime in the blockchain #1820

    bool IsFinal(int nBlockHeight=0, int64 nBlockTime=0) const
    {
        // Time based nLockTime implemented in 0.1.6
        if (nLockTime == 0)
            return true;   
        if (nBlockHeight == 0)
            nBlockHeight = nBestHeight;
        if (nBlockTime == 0)
            nBlockTime = GetAdjustedTime();
        if ((int64)nLockTime < ((int64)nLockTime < LOCKTIME_THRESHOLD ? (int64)nBlockHeight : nBlockTime))
            return true;
        BOOST_FOREACH(const CTxIn& txin, vin)
            if (!txin.IsFinal())
                return false;   
        return true;
    }

IsFinal() can never return false. The final return true should be return false and the input check should come before the time check (or left where it is and had its sense reversed). Would be a trivial fix except its a soft-forking change. ... and will probably require bumping the transaction version number as well as updating the block enforcing rules.

It's well known that replacement didn't work, but nLockTime not being enforced in the chain was a surprise to me

13e100dd08b6da0a7426ea520b0bb3ae54cef79dd045e2e4f7116023df3a5c95 is an example of a violating transaction in the chain.

How do you mean IsFinal() can never return false? If you want a non-final transaction, at least one transaction input should have a non-maximum nSequence number.

Doh. Missed that it was calling the ctxin IsFinal not itself.