BIP-112: Mempool-only CHECKSEQUENCEVERIFY #7524

1. 
   btcdrak commented at 5:29 pm on February 12, 2016: contributor

   Replace NOP3 with CHECKSEQUENCEVERIFY (BIP-112)

   The BIP text is at https://github.com/bitcoin/bips/blob/master/bip-0112.mediawiki

   This PR follows on from #6564 and is rebased (with #7184 which has been merged top master) so can now be tested directly.

   Functional test scripts by @ajtowns can be found at https://github.com/ajtowns/op_csv-test

   For reviewers please note that #6564 remained unchanged for several months. The list of reviews in #6564 were as follows:

   • Kanzure utACK
   • rustyrussell utACK
   • instagibbs utACK
   • dcousens utACK
   • rubensayshi utACK
   • afk11 utACK
   • jgarzik utACK
   • greenaddress utACK
   • rustyrussel Tested ACK
   • ajtowns Tested ACK
   • josephpoon Tested ACK
   • CodeShark Tested ACK
   • NicolasDorier Tested ACK
2. 
   morcos commented at 8:45 pm on February 12, 2016: member

   My comment remains that I would prefer VerifyLockTime not be encapsulated for reuse for nLockTime and nSequence checks.
3. 
   btcdrak commented at 6:39 am on February 13, 2016: contributor

   @morcos @petertodd I agree the encapsulation hampers readability. I propose something like 2fcd56f.
4. 
   NicolasDorier commented at 7:22 am on February 13, 2016: contributor

   ACK 2fcd56f
5. 
   instagibbs commented at 2:56 pm on February 13, 2016: member

   utACK https://github.com/btcdrak/bitcoin/commit/2fcd56f70845e9c78ab3ffde38fbb11ccf33e6da
6. BIP112: Implement CHECKSEQUENCEVERIFY

   - Replace NOP3 with CHECKSEQUENCEVERIFY (BIP112)
     <nSequence> CHECKSEQUENCEVERIFY -> <nSequence>
   - Fails if txin.nSequence < nSequence, allowing funds of a txout to be locked for a number of blocks or a duration of time after its inclusion in a block.
   - Pull most of CheckLockTime() out into VerifyLockTime(), a local function that will be reused for CheckSequence()
   - Add bitwise AND operator to CScriptNum
   - Enable CHECKSEQUENCEVERIFY as a standard script verify flag
   - Transactions that fail CSV verification will be rejected from the mempool, making it easy to test the feature. However blocks containing "invalid" CSV-using transactions will still be accepted; this is *not* the soft-fork required to actually enable CSV for production use.

   53e53a33c9
7. Separate CheckLockTime() and CheckSequence() logic

   For the sake of a little repetition, make code more readable.

   c3c375226e
8. btcdrak force-pushed on Feb 14, 2016
9. 
   btcdrak commented at 7:43 pm on February 14, 2016: contributor

   I’ve squashed to two commits. 53e53a3 corresponds to the state of #6564 as per OP and c3c3752 (was 2fcd56f) addresses request from @morcos and @petertodd.

   Previous branch state for verification checksequenceverify_2fcd56f.

10. laanwj added the label Mempool on Feb 15, 2016
11. laanwj added the label TX fees and policy on Feb 15, 2016
12. in src/script/interpreter.cpp: in c3c375226e outdated

    1226+    // the nSequenceMasked in the transaction.
    1227+    if (!(
    1228+        (txToSequenceMasked <  CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG && nSequenceMasked <  CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG) ||
    1229+        (txToSequenceMasked >= CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG && nSequenceMasked >= CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG)
    1230+    ))
    1231+        return false;
    

    ---

    ---

    

    laanwj commented at 9:09 am on February 16, 2016:

    This return false here seems to come out of the blue, which could make people misread the code and introduce bugs. I’d suggest adding the )) to the line before it, or surrounding with {}.
13. 
    laanwj commented at 9:24 am on February 16, 2016: member

    utACK 2fcd56f
14. Code style fix.

    This if statement is a little obtuse and using braces here
    improves readability.

    a38107643f
15. laanwj merged this on Feb 16, 2016
16. laanwj closed this on Feb 16, 2016

    ---

17. laanwj referenced this in commit 93c85d458a on Feb 16, 2016
18. btcdrak deleted the branch on Dec 3, 2016
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20. wqking referenced this in commit b63acd8e7f on Apr 26, 2018
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27. wqking referenced this in commit 1fde81f71d on Apr 4, 2021
28. wqking referenced this in commit e506572175 on Apr 4, 2021
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Contributors
btcdrak morcos NicolasDorier instagibbs laanwj

Labels
TX fees and policy Mempool