Mining interface: getCoinbaseMerklePath() and submitSolution() #30955

1. 
   Sjors commented at 7:55 am on September 24, 2024: member

   The new BlockTemplate interface introduced in #30440 allows for a more efficient way for a miner to submit the block solution. Instead of having the send the full block, it only needs to provide the nonce, timestamp, version fields and coinbase transaction.

   This PR introduces submitSolution() for that. It’s currently unused.

   #29432 and https://github.com/Sjors/bitcoin/pull/48 use it to process the Stratum v2 message SubmitSolution. The method should be sufficiently generic to work with alternative mining protocols (none exist that I’m aware off).

   This PR also introduces getCoinbaseMerklePath(), which is needed in Stratum v2 to construct the merkle_path field of the NewTemplate message (see spec). The coinbase merkle path is also used in Stratum “v1”, see e.g. https://bitcoin.stackexchange.com/questions/109820/questions-on-merkle-root-hashing-for-stratum-pools

   This last function uses BlockMerkleBranch which was moved to the test code in #13191. The reason back then for moving it was that it was no longer used. This PR moves it back.

   This PR does not change behaviour since both methods are unused.

2. 
   DrahtBot commented at 7:55 am on September 24, 2024: contributor

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   Type	Reviewers
   ACK	itornaza
   Concept ACK	TheCharlatan, tdb3

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3. 
   TheCharlatan commented at 8:19 am on September 24, 2024: contributor

   Concept ACK
4. 
   tdb3 commented at 10:27 am on September 24, 2024: contributor

   Concept ACK
5. Panga9309 approved
6. Move BlockMerkleBranch back to merkle.{h,cpp}

   The Mining interface uses this function in the next commit
   to calculate the coinbase merkle path. Stratum v2 uses
   this to send a compact work template.
   
   This partially undoes the change in 4defdfab94504018f822dc34a313ad26cedc8255,
   but is not a revert, because the implementation changed in the meantime.
   
   This commit also documents the function.

   63d6ad7c89
7. Add getCoinbaseMerklePath() to Mining interface 47b4875ef0
8. Add submitSolution to BlockTemplate interface 525e9dcba0
9. Sjors force-pushed on Sep 26, 2024
10. 
    Sjors commented at 8:05 am on September 26, 2024: member

    Rebased after #30510.
11. itornaza approved
12. 
    itornaza commented at 8:22 am on September 26, 2024: contributor

    Code review ACK 525e9dcba0b8c6744bcd3725864f39786afc8ed5

    In order to verify that MerkleComputation(), ComputeMerkleBranch(), BlockMerkleBranch() were copied verbatim from their resting place at src/test/merkle_tests.cpp to their new home src/consensus/merkle.cpp, I copied the two versions of the functions in separate files and compared them with diff. The only difference I noticed is that now the function BlockMerkleBranch() is not declared as static which is correct, because we want to be using it from outside it’s compilation unit, like for example from src/node/interfaces.cpp. Built the pr locally and run all unit functional and extended tests and all pass.

13. DrahtBot requested review from TheCharlatan on Sep 26, 2024
14. DrahtBot requested review from tdb3 on Sep 26, 2024
15. 
    Sjors commented at 8:24 am on September 26, 2024: member

    @itornaza you may also find git diff --color-moved=dimmed-zebra useful.

Contributors
Sjors DrahtBot TheCharlatan tdb3 Panga9309 itornaza

Review Requested
TheCharlatan tdb3