Reduced Data Temporary Softfork, implemented as a modified BIP9 temporary deployment by dathonohm · Pull Request #238 · bitcoinknots/bitcoin

dathonohm · 2025-11-24T22:13:14Z

ReducedData Temporary Softfork (BIP-110/RDTS)

Implementation of BIP-110 for Bitcoin Knots.

Versionbits extensions

max_activation_height (mutually exclusive with timeout) with BIP8/148-style mandatory signaling enforcement
active_duration for temporary deployments (expiry after ~1 year) and a corresponding EXPIRED BIP9 state
Per-deployment activation threshold (55% for RDTS instead of global 95%)

Consensus rules (when DEPLOYMENT_REDUCED_DATA is active)

Output scripts limited to 34 bytes (OP_RETURN limited to 83 bytes)
Data push size limit reduced to 256 bytes (SCRIPT_VERIFY_REDUCED_DATA), except BIP16 redeemScript
DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM, DISCOURAGE_UPGRADABLE_TAPROOT_VERSION, DISCOURAGE_OP_SUCCESS enforced at consensus level
Taproot annex forbidden
Taproot control block limited to 257 bytes (tree depth 7)
OP_IF/OP_NOTIF forbidden in Tapscript
Empty witness required for P2A spends
UTXO-height exemption: inputs spending UTXOs created before activation are exempt from script rules

Other features

The above rules are enforced unconditionally in policy
NODE_REDUCED_DATA service bit (bit 27) with preferential peering
DNS seed filtering for BIP-110 nodes (x8000009)
Up to 2 non-BIP110 outbound peers allowed

Commit structure (34 commits)

The commits have been structured such that every commit passes all tests (except for the coin_age_priority UBSan issue which is fixed outside this PR). The BIP9 modifications are placed first, since the actual consensus validation changes depend on the existence of DEPLOYMENT_REDUCED_DATA (originally a buried deployment).

Two commits are intentionally large because their changes break a large amount of tests, so test adaptations that must land atomically are bundled: 45c004e30e and 983555f940.

GregTonoski · 2025-11-25T12:46:41Z

Let me suggest adding a note that OP_RETURN is deprecated in help texts, please.

cal-gooo · 2025-11-30T14:33:49Z

what's the timeline to get this merged so the signaling can use this implementation?

dathonohm · 2025-12-01T15:34:54Z

There is no specific timeline to get this merged into Knots, as it is not confirmed that it will be eligible for merging, even when complete. However, I am aiming to have this draft ready for review in the next few days.

Miner signaling can still use this deployment if the activation client is released after the start of the signaling period (which is today, so this will definitely happen).

dathonohm · 2025-12-02T21:52:52Z

All comments from #234 are now addressed.

Undrafting since the code is relatively stable now.

Still needs rebase.

dathonohm · 2025-12-02T22:05:06Z

@GregTonoski

Let me suggest adding a note that OP_RETURN is deprecated in help texts, please.

OP_RETURN is not deprecated; it is merely limited to 83 bytes in consensus.

dathonohm · 2025-12-03T05:39:45Z

Rebased on v29.2.knots20251110.

Ready for review.

stackingsaunter · 2025-12-03T20:03:23Z

Concept NACK

There shouldn't be any emergency softfork to address spam without at least a sketeched out permanent solution

dathonohm · 2025-12-03T20:44:32Z

@stackingsaunter Please keep conceptual discussion to the BIP PR. This PR is for code review only.

luke-jr

Review not complete yet

dathonohm · 2026-01-03T03:01:27Z

All review comments are now addressed.

CI is now fully passing (except for the "test each commit" job).

A tag has been created for the current version, RC2 (identical to this branch except for the last commit, which updates the UA string for BIP-110).

Next I will make a release for RC2, and clean up the commit history here.

dathonohm · 2026-01-13T01:48:18Z

I have begun work on RC3.

RC2's branch is archived here (the prior state of this PR, commit 5a54af7, is the penultimate commit on that branch).

RC3 will include some minor improvements to peer discovery and the guix build, as well as better testing against non-110 peers.

luke-jr · 2026-02-05T19:57:39Z

Let me suggest adding a note that OP_RETURN is deprecated in help texts, please.

OP_RETURN is not deprecated; it is merely limited to 83 bytes in consensus.

datacarriersize is not deprecated, but OP_RETURN is. Documenting it is out of scope for this PR, though.

luke-jr

Would prefer to squash/eliminate things like the UA changes and BIP444 references (added and replaced).

note to self: this review was up to f4045f3

luke-jr · 2026-02-06T20:56:57Z

    // at which all the in-chain inputs of the tx were included in blocks.
    // Typical usage of GetPriority with chainActive.Height() will ensure this.
-    int heightDiff = currentHeight - cachedHeight;
+    int heightDiff = int(currentHeight) - int(cachedHeight);


Why is this needed?

Fixes UBSan unsigned integer overflow: 432 - 433 can't be represented in unsigned int (https://github.com/dathonohm/bitcoin/actions/runs/19997804442, ASan+UBSan job). The cast makes the subtraction signed so the dResult < 0 check on line 114 works correctly. Same pattern as line 70 in the same file (introduced in 28b7673).

As the comment says, calling this with a currentHeight < cachedHeight is invalid...

Removing this commit to expose the failure, then I'll work on a fix. This is an upstream bug.

Github-Pull: #238 Rebased-From: 88c569d

Github-Pull: #238 Rebased-From: becf3de

…ployments Github-Pull: #238 Rebased-From: 6a57462

…eight and set vbrequired during mandatory signaling Github-Pull: #238 Rebased-From: 1bf0c35

…Taproot logic; adapt tests Co-Authored-By: Dathon Ohm <dathonohm@proton.me> Github-Pull: #238 Rebased-From: f664525

Co-Authored-By: Dathon Ohm <dathonohm@proton.me> Github-Pull: #238 Rebased-From: 41abcea

…to reduce data push size limit to 256 bytes (except for P2SH redeemScript push); adapt tests Co-Authored-By: Dathon Ohm <dathonohm@proton.me> Co-Authored-By: Léo Haf <leo@haf.ovh> Github-Pull: #238 Rebased-From: f595e6a

Github-Pull: #238 Rebased-From: 9efe141

…ill unused) Co-Authored-By: Dathon Ohm <dathonohm@proton.me> Co-Authored-By: Léo Haf <leo@haf.ovh> Github-Pull: #238 Rebased-From: e1ae973

…DUCED_DATA (still unused) Github-Pull: #238 Rebased-From: 4743b66

Github-Pull: #238 Rebased-From: 1984769

Github-Pull: #238 Rebased-From: f58d34b

…o cap output scripts at 83 bytes Github-Pull: #238 Rebased-From: 34621ba

…l never), limit non-OP_RETURN scripts to 34 bytes and OP_RETURN outputs to 83 bytes MAX_OUTPUT_DATA_SIZE constant definition moved here from its original commit (4a8d8d0) due to commit reordering. Co-Authored-By: Dathon Ohm <dathonohm@proton.me> Github-Pull: #238 Rebased-From: 091c18c

Github-Pull: #238 Rebased-From: d220041

Github-Pull: #238 Rebased-From: 7860d8d

…ATA is active Github-Pull: #238 Rebased-From: 0c9c50e

…T_REDUCED_DATA is active; adapt tests Wire OutputSizeLimit to deployment with unconditional mempool enforcement. Adapt test framework and functional tests for 34-byte output script limit and 83-byte OP_RETURN limit. Test fixes from: 8257367, c609a45, 9194f6f, b141420, e011d53, fc62079, a065a59, 4f371cf, 5ee8102, ebe821e (partial) Co-Authored-By: Dathon Ohm <dathonohm@proton.me> Co-Authored-By: 3c853b6299 <3c853b6299@pm.me> Co-Authored-By: moneybadger1 <moneybadger1@proton.me> Co-Authored-By: Léo Haf <leohaf@orangepill.ovh> Github-Pull: #238 Rebased-From: 45c004e

Github-Pull: #238 Rebased-From: 224c1c3

…AM,UPGRADABLE_TAPROOT_VERSION,OP_SUCCESS} on blocks when DEPLOYMENT_REDUCED_DATA is active Co-Authored-By: Léo Haf <leo@haf.ovh> Co-Authored-By: Dathon Ohm <dathonohm@proton.me> Github-Pull: #238 Rebased-From: 881d4ab

…TORY_VERIFY_FLAGS Github-Pull: #238 Rebased-From: 286a923

…ation flags on a per-input basis Github-Pull: #238 Rebased-From: 48118a7

…height from reduced_data script validation rules Bugfix: validation: Do not cache the result of CheckInputScripts if flags_per_input is used (and avoid using it when unnecessary) Co-Authored-By: Dathon Ohm <dathonohm@proton.me> Co-Authored-By: Lőrinc <pap.lorinc@gmail.com> Github-Pull: #238 Rebased-From: 71722a2

Co-Authored-By: Dathon Ohm <dathonohm@proton.me> Co-Authored-By: Léo Haf <leohaf@orangepill.ovh> Github-Pull: #238 Rebased-From: a6ac602

Co-Authored-By: Léo Haf <leohaf@orangepill.ovh> Co-Authored-By: Lőrinc <pap.lorinc@gmail.com> Github-Pull: #238 Rebased-From: 3428f6c

Co-Authored-By: Léo Haf <leohaf@orangepill.ovh> Github-Pull: #238 Rebased-From: 14dd104

Github-Pull: #238 Rebased-From: 1b1ef4f

…BLE_WITNESS_PROGRAM,UPGRADABLE_TAPROOT_VERSION,OP_SUCCESS} Github-Pull: #238 Rebased-From: 90760ff

…x8000009; adapt tests Squash of: - b662a23 Define a service bit for BIP148 - 0db5282 Add questionmark to end of BIP148 service bit string, and add to bitcoin-cli - b5a77cd Preferentially peer with nodes enforcing RDTS; rename BIP148 references to ReducedData; adapt tests - 85289a3 net: ask DNS seed for x8000009 (original: ea8c1ee) Define a service bit for BIP148 Github-Pull: bitcoin#10532 Rebased-From: cd74a23fcf9588199e196ab31bc64972400c2027 Add questionmark to end of BIP148 service bit string, and add to bitcoin-cli Preferentially peer with nodes enforcing RDTS; rename BIP148 references to ReducedData; adapt tests Combines: preferential peering (367b344), BIP148->ReducedData rename (85a78b8), service bit test fixes (f98fe90, ebe821e, 5efab4a, 4b757d8, f648a21). net: ask DNS seed for x8000009 Co-Authored-By: Luke Dashjr <luke-jr+git@utopios.org> Co-Authored-By: 3c853b6299 <3c853b6299@pm.me> Co-Authored-By: Léo Haf <leohaf@orangepill.ovh> Github-Pull: #238 Rebased-From: 983555f

Github-Pull: #238 Rebased-From: f62f5fd

dathonohm mentioned this pull request Nov 24, 2025

ReducedData Temporary Softfork #234

Closed

kwsantiago reviewed Nov 25, 2025

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dathonohm mentioned this pull request Nov 26, 2025

BIP 110: Reduced Data Temporary Softfork bitcoin/bips#2017

Merged

dathonohm marked this pull request as ready for review December 2, 2025 23:29

dathonohm force-pushed the uasf-modified-bip9 branch from df70e59 to d699af3 Compare December 3, 2025 05:38

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luke-jr requested changes Dec 23, 2025

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dathonohm requested a review from luke-jr December 27, 2025 02:59

dathonohm force-pushed the uasf-modified-bip9 branch from 994b2fe to 5a54af7 Compare January 1, 2026 01:33

luke-jr added the high priority label Jan 8, 2026

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Comment thread src/txmempool.cpp

Comment thread test/functional/rpc_net.py

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dathonohm force-pushed the uasf-modified-bip9 branch from 5a54af7 to cc089c4 Compare January 13, 2026 01:28

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luke-jr mentioned this pull request Feb 9, 2026

Prompt user after upgrading to RDTS-enabled version #256

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dathonohm force-pushed the uasf-modified-bip9 branch from f4045f3 to 1d3cdac Compare February 12, 2026 22:02

luke-jr pushed a commit that referenced this pull request Apr 15, 2026

versionbits: add per-deployment activation threshold

3579ef6

Github-Pull: #238 Rebased-From: 88c569d

luke-jr pushed a commit that referenced this pull request Apr 15, 2026

chainparams: support regtest vbparams for per-deployment threshold

ef348fa

Github-Pull: #238 Rebased-From: becf3de

luke-jr pushed a commit that referenced this pull request Apr 15, 2026

versionbits: add EXPIRED state to BIP9 state machine for temporary de…

85c828a

…ployments Github-Pull: #238 Rebased-From: 6a57462

luke-jr pushed a commit that referenced this pull request Apr 15, 2026

versionbits: add mandatory signaling enforcement for max_activation_h…

2108d25

…eight and set vbrequired during mandatory signaling Github-Pull: #238 Rebased-From: 1bf0c35

luke-jr added a commit that referenced this pull request Apr 15, 2026

script: use TAPROOT_CONTROL_MAX_NODE_COUNT_REDUCED for non-consensus …

9320eba

…Taproot logic; adapt tests Co-Authored-By: Dathon Ohm <dathonohm@proton.me> Github-Pull: #238 Rebased-From: f664525

luke-jr added a commit that referenced this pull request Apr 15, 2026

policy: enforce SCRIPT_VERIFY_REDUCED_DATA as a policy rule

2fdc045

Co-Authored-By: Dathon Ohm <dathonohm@proton.me> Github-Pull: #238 Rebased-From: 41abcea

luke-jr added a commit that referenced this pull request Apr 15, 2026

script: forbid Taproot annex with SCRIPT_VERIFY_REDUCED_DATA

e471965

Github-Pull: #238 Rebased-From: 9efe141

luke-jr added a commit that referenced this pull request Apr 15, 2026

script: Limit Taproot control block to 257 bytes for SCRIPT_VERIFY_RE…

2f7b0d4

…DUCED_DATA (still unused) Github-Pull: #238 Rebased-From: 4743b66

luke-jr pushed a commit that referenced this pull request Apr 15, 2026

script: require empty witness for P2A spends

c536694

Github-Pull: #238 Rebased-From: 1984769

luke-jr added a commit that referenced this pull request Apr 15, 2026

consensus: Add no-op flags to CheckTxInputs function

2ec384f

Github-Pull: #238 Rebased-From: f58d34b

luke-jr added a commit that referenced this pull request Apr 15, 2026

consensus: Define CheckTxInputsRules::OutputSizeLimit flag (unused) t…

28672cf

…o cap output scripts at 83 bytes Github-Pull: #238 Rebased-From: 34621ba

luke-jr added a commit that referenced this pull request Apr 15, 2026

policy: limit datacarriersize config to MAX_OUTPUT_DATA_SIZE (=83 B)

032f3ae

Github-Pull: #238 Rebased-From: d220041

luke-jr pushed a commit that referenced this pull request Apr 15, 2026

chainparams: add DEPLOYMENT_REDUCED_DATA temporary BIP9 deployment

c5b967a

Github-Pull: #238 Rebased-From: 7860d8d

luke-jr added a commit that referenced this pull request Apr 15, 2026

consensus: Enforce SCRIPT_VERIFY_REDUCED_DATA if DEPLOYMENT_REDUCED_D…

9f3bb4a

…ATA is active Github-Pull: #238 Rebased-From: 0c9c50e

luke-jr pushed a commit that referenced this pull request Apr 15, 2026

consensus: apply output size limit to generation transactions

de83ad4

Github-Pull: #238 Rebased-From: 224c1c3

luke-jr added a commit that referenced this pull request Apr 15, 2026

Refactor: Include all reduced_data verify flags in REDUCED_DATA_MANDA…

d6fe206

…TORY_VERIFY_FLAGS Github-Pull: #238 Rebased-From: 286a923

luke-jr added a commit that referenced this pull request Apr 15, 2026

validation: Extend CheckInputScripts to allow overriding script valid…

c547e67

…ation flags on a per-input basis Github-Pull: #238 Rebased-From: 48118a7

luke-jr pushed a commit that referenced this pull request Apr 15, 2026

test: implement functional tests for ReducedData Spec

8084b23

Co-Authored-By: Dathon Ohm <dathonohm@proton.me> Co-Authored-By: Léo Haf <leohaf@orangepill.ovh> Github-Pull: #238 Rebased-From: a6ac602

luke-jr pushed a commit that referenced this pull request Apr 15, 2026

test: Add UTXO height-based REDUCED_DATA enforcement test

e77c5f6

Co-Authored-By: Léo Haf <leohaf@orangepill.ovh> Co-Authored-By: Lőrinc <pap.lorinc@gmail.com> Github-Pull: #238 Rebased-From: 3428f6c

luke-jr pushed a commit that referenced this pull request Apr 15, 2026

test: add functional tests for modified BIP9 temporary deployment

5eedc73

Co-Authored-By: Léo Haf <leohaf@orangepill.ovh> Github-Pull: #238 Rebased-From: 14dd104

luke-jr pushed a commit that referenced this pull request Apr 15, 2026

doc: add BIP-110 to bips.md

35ec869

Github-Pull: #238 Rebased-From: 1b1ef4f

luke-jr added a commit that referenced this pull request Apr 15, 2026

Policy: Do not allow user to bypass SCRIPT_VERIFY_DISCOURAGE_{UPGRADA…

736d10d

…BLE_WITNESS_PROGRAM,UPGRADABLE_TAPROOT_VERSION,OP_SUCCESS} Github-Pull: #238 Rebased-From: 90760ff

luke-jr pushed a commit that referenced this pull request Apr 15, 2026

net: allow up to 2 non-BIP110 outbound peers

71965a5

Github-Pull: #238 Rebased-From: f62f5fd

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dathonohm commented Nov 24, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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ReducedData Temporary Softfork (BIP-110/RDTS)

Versionbits extensions

Consensus rules (when DEPLOYMENT_REDUCED_DATA is active)

Other features

Commit structure (34 commits)

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GregTonoski commented Nov 25, 2025

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