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[miner] omit dummy extraNonce via IPC

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Previously the coinbase transaction generated by our miner code was
not used downstream, because the getblocktemplate RPC excludes it.

Since the Mining IPC interface was introduced in #30200 we do expose
this dummy coinbase transaction. In Stratum v2 several parts of it
are communicated downstream, including the scriptSig.

This commit removes the dummy extraNonce from the coinbase scriptSig
in block templates requested via IPC. This limits the scriptSig
to what is essential for consensus (BIP34) and removes the need for
external mining software to remove the dummy, or even ignore
the scriptSig we provide and generate it some other way. This
could cause problems if a future soft fork requires additional
data to be committed here.

A test is added to verify the new IPC behavior.

It achieves this by introducing an include_dummy_extranonce
option which defaults to false with all test code updated to
set it to true. Because this option is not exposed via IPC,
callers will no longer see it.

The caller needs to ensure that for blocks 1 through 16
they pad the scriptSig in order to avoid bad-cb-length.

Co-authored-by: Anthony Towns <aj@erisian.com.au>
This commit is contained in:
Sjors Provoost
2026-01-14 10:02:33 +01:00
parent bf3b5d6d06
commit d511adb664
17 changed files with 55 additions and 12 deletions
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17
src/node/miner.cpp
View File

@@ -177,11 +177,17 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock()
coinbase_tx.block_reward_remaining = block_reward;
// Start the coinbase scriptSig with the block height as required by BIP34.
// The trailing OP_0 (historically an extranonce) is optional padding and
// could be removed without a consensus change. Mining clients are expected
// to append extra data to this prefix, so increasing its length would reduce
// the space they can use and may break existing clients.
coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
// Mining clients are expected to append extra data to this prefix, so
// increasing its length would reduce the space they can use and may break
// existing clients.
coinbaseTx.vin[0].scriptSig = CScript() << nHeight;
if (m_options.include_dummy_extranonce) {
// For blocks at heights <= 16, the BIP34-encoded height alone is only
// one byte. Consensus requires coinbase scriptSigs to be at least two
// bytes long (bad-cb-length), so tests and regtest include a dummy
// extraNonce (OP_0)
coinbaseTx.vin[0].scriptSig << OP_0;
}
coinbase_tx.script_sig_prefix = coinbaseTx.vin[0].scriptSig;
Assert(nHeight > 0);
coinbaseTx.nLockTime = static_cast<uint32_t>(nHeight - 1);
@@ -212,6 +218,7 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock()
pblock->nNonce = 0;
if (m_options.test_block_validity) {
// if nHeight <= 16, and include_dummy_extranonce=false this will fail due to bad-cb-length.
if (BlockValidationState state{TestBlockValidity(m_chainstate, *pblock, /*check_pow=*/false, /*check_merkle_root=*/false)}; !state.IsValid()) {
throw std::runtime_error(strprintf("TestBlockValidity failed: %s", state.ToString()));
}

4
src/node/types.h
View File

@@ -67,6 +67,10 @@ struct BlockCreateOptions {
* coinbase_max_additional_weight and coinbase_output_max_additional_sigops.
*/
CScript coinbase_output_script{CScript() << OP_TRUE};
/**
* Whether to include an OP_0 as a dummy extraNonce in the template's coinbase
*/
bool include_dummy_extranonce{false};
};
struct BlockWaitOptions {