policy: Allow non-standard scripts with -acceptnonstdtxn=1 (test nets only) #29843

1. 
   ajtowns commented at 9:08 am on April 10, 2024: contributor

   This PR changes -acceptnonstdtxn=1 so that it also skips the non-mandatory script checks, allowing txs that (eg) use OP_NOPx or OP_SUCCESS into the mempool. This remains only available on test nets.
2. 
   DrahtBot commented at 9:08 am on April 10, 2024: contributor

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   Type	Reviewers
   Concept ACK	1440000bytes, benthecarman, glozow

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3. DrahtBot added the label TX fees and policy on Apr 10, 2024
4. 
   ajtowns commented at 9:15 am on April 10, 2024: contributor

   Previous discussion in #28334.

   If you enable this feature as a non-mining node, you risk having txs pinned in your mempool that conflict or double-spend standard txs in the normal mempool, which may cause problems with applications or layer-2 protocols.

   If you enable this feature as a mining node, you have a small risk of ending up with invalid txs remaining in your mempool if a tx non-standard tx is accepted in your mempool and remains in there during a soft-fork activation that renders the tx invalid. At that point if that tx is included in blocks you generate, they will be invalid.

   For these reasons this feature continues to only be available on test nets, not mainnet.

   Having this be available in mainline bitcoin may make it easier to observe test transactions using proposed new soft-fork features (eg OP_CAT or SIGHASH_APO is enabled via the inquisition client which considers those txs standard, but the mainline client will consider them non-standard and has no option to accept them). discussion link

5. ajtowns requested review from instagibbs on Apr 10, 2024
6. 
   1440000bytes commented at 7:02 pm on April 12, 2024: none

   Concept ACK
7. 
   benthecarman commented at 7:36 pm on April 12, 2024: contributor

   Concept ACK this would be nice for testing soft forks on test networks
8. 
   luke-jr commented at 1:44 am on April 21, 2024: member

   Seems like this goes beyond the expected behaviour. Maybe make it =2 at least?
9. 
   glozow commented at 11:20 am on April 22, 2024: member

   concept ACK fwiw
10. 
    instagibbs commented at 1:53 pm on April 22, 2024: member

    Seems like this goes beyond the expected behaviour. Maybe make it =2 at least?

    Since these are test-network-only changes, are we required to preserve current behavior?

11. 
    twosatsmaxi commented at 3:54 pm on April 25, 2024: none

    Following.
12. DrahtBot added the label CI failed on May 15, 2024
13. 
    DrahtBot commented at 0:51 am on May 15, 2024: contributor

    🚧 At least one of the CI tasks failed. Make sure to run all tests locally, according to the documentation.

    Possibly this is due to a silent merge conflict (the changes in this pull request being incompatible with the current code in the target branch). If so, make sure to rebase on the latest commit of the target branch.

    Leave a comment here, if you need help tracking down a confusing failure.

    Debug: https://github.com/bitcoin/bitcoin/runs/23651574970

14. tests: in p2p_segwit, check non-mandatory errors with -acceptnonstdtxn=0 node

    Prepare for updating -acceptnonstdtxn to allow txns that violate
    STANDARD_SCRIPT_VERIFY_FLAGS but not MANDATORY_SCRIPT_VERIFY_FLAGS by
    checking the non-mandatory flags with node that enforces standardness.

    3118c2e365
15. validation: Check only MANDATORY_SCRIPT_VERIFY_FLAGS when -acceptnonstdtxn is set affee04f7a
16. ajtowns force-pushed on May 16, 2024
17. 
    ajtowns commented at 3:54 pm on May 16, 2024: contributor

    Bumped past #29086
18. DrahtBot removed the label CI failed on May 16, 2024
19. 
    luke-jr commented at 1:43 am on June 8, 2024: member

    Since these are test-network-only changes, are we required to preserve current behavior?

    Whether you are required to or not, it is the correct thing to do. This option originated in Knots where it has always been available on mainnet, and expected to not enable upgradable opcodes/etc.

20. achow101 requested review from glozow on Oct 15, 2024

Contributors
ajtowns DrahtBot 1440000bytes benthecarman luke-jr glozow instagibbs twosatsmaxi

Review Requested
instagibbs glozow

Labels
TX fees and policy