rpc: use anti-fee-sniping in send, sendall and walletcreatefundedpsbt #32892

1. 
   Sjors commented at 2:55 pm on July 7, 2025: member

   If the user does not specify locktime for send, sendall and walletcreatefundedpsbt, enable anti-fee-sniping. Previously we would set nLockTime to 0.

   This behavior matches the sendtoaddress RPC and the GUI wallet.

   Because sendall doesn’t use CreateTransactionInternal this PR refactors (and renames) DiscourageFeeSniping so that it checks input nSequence values and nLockTime by itself, and brings its own FastRandomContext. A subsequent commit then calls this from the sendall RPC.

2. DrahtBot added the label RPC/REST/ZMQ on Jul 7, 2025
3. 
   DrahtBot commented at 2:55 pm on July 7, 2025: contributor

   The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/32892.

   Reviews

   See the guideline for information on the review process. A summary of reviews will appear here.

   Conflicts

   Reviewers, this pull request conflicts with the following ones:

   • #32896 (wallet, rpc: add v3 transaction creation and wallet support by ishaanam)
   • #32857 (wallet: allow skipping script paths by Sjors)
   • #31936 (rpc: Support v3 raw transactions creation by Bue-von-hon)
   • #28944 (wallet, rpc: add anti-fee-sniping to send and sendall by ishaanam)
   • #21283 (Implement BIP 370 PSBTv2 by achow101)

   If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

4. rpc: use anti-fee-sniping in send and walletcreatepsbt

   If the user does not specify 'locktime' for send and
   walletcreatefundedpsbt, enable anti-fee-sniping. This matches
   sendtoaddress RPC behavior and the GUI wallet.

   d1f1866c12
5. test: check anti fee sniping for send RPC c8a73f3c47
6. refactor: extract MaybeDiscourageFeeSniping helper

   Rename and refactor DiscourageFeeSniping such that it can determine
   by itself whether to apply anti fee sniping. This makes it easier
   to use outside of CreateTransactionInternal.

   642e4b6f37
7. rpc: use anti-fee-sniping in sendall 4bc0858202
8. doc: add release notes 113ba10627
9. Sjors force-pushed on Jul 7, 2025
10. 
    Sjors commented at 4:56 pm on July 7, 2025: member

    Expanded the existing test_anti_fee_sniping case in wallet_create_tx.py to cover send sendall. Making sendall actually work required an additional refactor.
11. Sjors renamed this:
    rpc: use anti-fee-sniping by default
    rpc: use anti-fee-sniping in send, sendall and walletcreatefundedpsbt
    on Jul 7, 2025
12. 
    glozow commented at 8:26 pm on July 7, 2025: member

    Any chance this is a duplicate of #28944?
13. 
    Sjors commented at 7:09 am on July 8, 2025: member

    @glozow thanks, I hadn’t seen that one. Will take a look.
14. 
    Sjors commented at 7:17 am on July 9, 2025: member

    Ok, so #28944 uses a completely different approach. It already has a lot of review, so I’ll add mine there.
15. Sjors closed this on Jul 9, 2025

    ---

16. in src/wallet/spend.cpp:948 in 113ba10627

    944@@ -945,9 +945,28 @@ static bool IsCurrentForAntiFeeSniping(interfaces::Chain& chain, const uint256&
    945  * Set a height-based locktime for new transactions (uses the height of the
    946  * current chain tip unless we are not synced with the current chain
    947  */
    948-static void DiscourageFeeSniping(CMutableTransaction& tx, FastRandomContext& rng_fast,
    

    ---

    ---

    

    Evoneem commented at 8:00 am on July 9, 2025:

    Anti free sniping on future merging please
17. 
    Evoneem commented at 8:01 am on July 9, 2025: none

    Anti free sniping on merges

Contributors
Sjors DrahtBot glozow Evoneem

Labels
RPC/REST/ZMQ