ipc: breaking but non-urgent changes #106
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Jassor909
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Nov 7, 2025
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Introduce a new method intended to replace getCoinbaseTx(), which provides a struct with everything clients need to construct a coinbase. This is safer than providing a raw dummy coinbase that clients then have to manipulate. A new helper method ExtractCoinbaseTemplate() processes the dummy coinbase transaction generated by BlockAssembler::CreateNewBlock and produces a CoinbaseTemplate. Expand the interface_ipc.py functional test to document its usage and ensure equivalence.
Add default_witness_commitment to CoinbaseTemplate for use in the getblocktemplate RPC.
Drop the following mining interface methods in favor of getCoinbase(): - getCoinbaseTx() - getCoinbaseCommitment() - getWitnessCommitmentIndex()
Clear dummy coinbase from block templates by default so it's not exposed to callers of getBlock(). Have RPC and test code opt-in to keeping the dummy coinbase where needed.
Adding a context parameter ensures that these methods are run in their own thread and don't block other calls. This is especially important for checkBlock() which may receive a slow to validate block from an untrusted origin (the IPC connection itself is assumed to trusted). This is a breaking change both ways: - clients must use the updated capnp file - updated clients can't call these methods on an unupgraded node
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Previously the dummy coinbase returned by the Mining IPC interface always had a witness and SegWit OP_RETURN output. This is unnecessary for empty blocks as well as for blocks without any SegWit spends. This commit makes this behavior configurable via always_add_coinbase_commitment on BlockCreateOptions. It defaults to false, making this a potentially breaking change to clients. The presence of this field in requests makes it incompatible with Bitcoin Core v30, so it's a breaking change in any case. Preserve historical getblocktemplate RPC behavior. Although it doesn't return a coinbase transaction, it does always provide a default_witness_commitment. This is set in BlockAssembler::CreateNewBlock() via a call GenerateCoinbaseCommitment(), which has the side-effect of adding a coinbase witness.
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I'll rebase after bitcoin#33880 lands to see if that fixes the failing jobs. |
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PR bitcoin#33936 fixes an important memory management bug, so it justifies a breaking change imo. If it lands then I might as well PR the other breaking changes here. |
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I plan to split these into standalone pull requests in due time.
Based on
Non-breaking commits
mining: deprecate getCoinbaseCommitment()
Its value is only used by the
getblocktemplateRPC and is redundant with therequired_outputsfields ofgetCoinbase()Breaking commits
mining: drop getCoinbaseTx(), etc
This drops three deprecated methods:
getCoinbaseTx()getCoinbaseCommitment()getWitnessCommitmentIndex()Pass context to
createNewBlock()andcheckBlock()Adding a
contextparameter ensures that these methods are run in their own thread and don't block other calls.This is especially important for checkBlock() which may receive a slow to validate block from an untrusted origin (the IPC connection itself is assumed to trusted).
This is a breaking change both ways:
Make non-mandatory coinbase commitment opt-in
This adds
always_add_coinbase_commitmenttoBlockCreateOptionsIt could be carefully documented to avoid making it a breaking change, by telling clients to omit it for older Bitcoin Core versions. But it's easier as a breaking change.
Part of the test is commented out pending the newly proposed
getCoinbase()method