rpc: fix getblock(header) returns target for tip

Sjors commented at 4:52 pm on September 20, 2025: member

A target field was added to the getblock and getblockheader RPC calls in #31583, but it mistakingly always used the tip value.

This PR fixes it to return the target for the given block. Because regtest does not have difficulty adjustment, the mainnet test is expanded to cover the fix.

A preliminary commit deals with mining block 2016 that’s needed for the test. It also:

renames the create_coinbase retarget_period argument to halving_period. Before #31583 this was hardcoded for regtest where these values are the same.
drops unused fees argument from mine helper
expands the CPU miner instructions for generating the alternative mainnet chain

Fixes #33440

DrahtBot added the label RPC/REST/ZMQ on Sep 20, 2025

DrahtBot commented at 4:52 pm on September 20, 2025: contributor

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

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For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/33446.

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ACK	luke-jr, sipa, TheCharlatan, ismaelsadeeq

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Sjors commented at 4:56 pm on September 20, 2025: member

This should probably be backported to v29 and v30.

test: add block 2016 to mock mainnet

The next commit requires an additional mainnet block which changes the difficulty.

Also fix a few minor mistakes in the test (suite):
- rename the create_coinbase retarger_period argument to halving_period. Before bitcoin#31583 this was hardcoded for regtest where these values are the same.
- drop unused fees argument from mine helper

Finally the CPU miner instructions for generating the alternative mainnet chain are expanded.

4c3c1f42cf

rpc: fix getblock(header) returns target for tip

A target field was added to the getblock and getblockheader RPC calls in bitcoin#31583, but it mistakingly always used the tip value.

Because regtest does not have difficulty adjustment, a test is added for mainnet instead.

bf7996cbc3

Sjors force-pushed on Sep 20, 2025

Sjors commented at 7:38 pm on September 20, 2025: member

I split 88fb025c83c7aa84766a5385e6a797102dd94513 in two commits: one that adds the mock mainnet block and updates the docs, and one that’s focussed on fixing the actual bug and adds test coverage for it (using this new block).

ismaelsadeeq commented at 5:07 pm on September 22, 2025: member

Concept ACK

luke-jr approved

luke-jr commented at 10:08 am on September 23, 2025: member

crACK bf7996cbc3becf329d8b1cd2f1007fec9b3a3188

DrahtBot requested review from ismaelsadeeq on Sep 23, 2025

luke-jr referenced this in commit 5ffd91a988 on Sep 23, 2025

luke-jr referenced this in commit 950b6beb56 on Sep 23, 2025

sipa commented at 12:12 pm on September 23, 2025: member

utACK bf7996cbc3becf329d8b1cd2f1007fec9b3a3188

maflcko added the label Needs backport (29.x) on Sep 24, 2025

maflcko added the label Needs backport (30.x) on Sep 24, 2025

in test/functional/data/README.md:11 in 4c3c1f42cf outdated

10@@ -11,17 +11,20 @@ The alternate mainnet chain was generated as follows:
11 - restart node with a faketime 2 minutes later

ismaelsadeeq commented at 11:56 am on September 24, 2025:

In “test: add block 2016 to mock mainnet” 4c3c1f42cf705e039751395799240da33ca969bd

nit: commit message typo s/retarger_period/retarget_period/g

Sjors commented at 1:03 pm on September 24, 2025:

Will change if I need to retouch.

TheCharlatan approved

TheCharlatan commented at 12:24 pm on September 24, 2025: contributor

ACK bf7996cbc3becf329d8b1cd2f1007fec9b3a3188

in test/functional/test_framework/blocktools.py:147 in 4c3c1f42cf outdated

143@@ -144,7 +144,7 @@ def script_BIP34_coinbase_height(height):
144     return CScript([CScriptNum(height)])
145 
146 
147-def create_coinbase(height, pubkey=None, *, script_pubkey=None, extra_output_script=None, fees=0, nValue=50, retarget_period=REGTEST_RETARGET_PERIOD):
148+def create_coinbase(height, pubkey=None, *, script_pubkey=None, extra_output_script=None, fees=0, nValue=50, halving_period=REGTEST_RETARGET_PERIOD):

ismaelsadeeq commented at 12:24 pm on September 24, 2025:

In “test: add block 2016 to mock mainnet” 4c3c1f42cf705e039751395799240da33ca969bd

This is a bit confusing @Sjors you updated the name to halving_period but still use the regtest retaget period constant.

The constant should be updated REGTEST_SUBSIDY_HALVING_INTERVAL for regtest and also define the interval for mainet too, it can be reused in other places.

Sjors commented at 1:01 pm on September 24, 2025:

I could rename it if I have to retouch, but at the time didn’t feel like adding another constant :-)

in test/functional/data/README.md:50 in 4c3c1f42cf outdated

42@@ -40,3 +43,8 @@ The timestamp was not kept constant because at difficulty 1 it's not sufficient
43 to only grind the nonce. Grinding the extra_nonce or version field instead
44 would have required additional (stratum) software. It would also make it more
45 complicated to reconstruct the blocks in this test.
46+
47+The `getblocktemplate` RPC code needs to be patched to ignore not being connected
48+to any peers, and to ignore the IBD status check.
49+
50+On macOS use `faketime "@$t"` instead.

ismaelsadeeq commented at 12:28 pm on September 24, 2025:

In “test: add block 2016 to mock mainnet” 4c3c1f42cf705e039751395799240da33ca969bd

Is this okay to be here? Shouldn’t it be in an issue to discuss the tradeoff and why those checks are added in the first place and why it should be removed?

Sjors commented at 1:02 pm on September 24, 2025:

It just describes how to generate the data for this test, I’m not proposing actually removing these checks in the repository.

ismaelsadeeq commented at 12:36 pm on September 24, 2025: member

Code review ACK bf7996cbc3becf329d8b1cd2f1007fec9b3a3188

Comments are on tests and doc

fanquake merged this on Sep 24, 2025

fanquake closed this on Sep 24, 2025

fanquake referenced this in commit 4ec30d53ec on Sep 24, 2025

fanquake referenced this in commit 1e348bc55a on Sep 24, 2025

fanquake removed the label Needs backport (30.x) on Sep 24, 2025

fanquake commented at 2:11 pm on September 24, 2025: member

Backported to 30.x in #33473.

fanquake removed the label Needs backport (29.x) on Sep 24, 2025

fanquake referenced this in commit 118abf4c30 on Sep 24, 2025

fanquake referenced this in commit 22ab141243 on Sep 24, 2025

fanquake commented at 2:41 pm on September 24, 2025: member

Backported to 29.x in #33474.

Sjors deleted the branch on Sep 24, 2025

rpc: fix getblock(header) returns target for tip #33446

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