feat(params,core,consensus,eth,cmd): add gas2500x fork switch

[gzliudan]

Proposed changes

Summary

Introduce an optional Gas2500xBlock fork that raises the XDC gas schedule from the Gas50x tier (12.5 gwei) to the Gas2500x tier (625 gwei), scaling the chain default gas price and the EIP-1559 base fee together.

Motivation & design

• Gas tier resolution is refactored into a single ordered table in params/gas.go, so a future tier only needs one more row.
• TRC21 gas price, gas fee and chain default gas price queries resolve the active tier instead of testing Gas50xBlock directly.
• Every tier, including the pool floor returned by GetMinGasPrice, is scaled from the immutable common.DefaultMinGasPrice; the cached params.SetMinGasPrice50x and the mutable common.MinGasPrice it was derived from are removed.
• The EIP-1559 base fee becomes block-number aware: CalcBaseFee is expressed in terms of CalcBaseFeeForBlockNumber, and common.BaseFee is replaced by params.BaseFeeForBlock.
• Callers that price a not-yet-mined transaction (txpool promotion/demotion/reorg, ValidateTransactionWithState, gas price oracle, fee history, pending tx RPC) now resolve the schedule at the next block height instead of the current head.
• The BASEFEE opcode now reports the header base fee; where the header carries none (the London-to-EIP1559 window) it falls back to the pinned params.BaseFeeForOpcode. CheckConfigForkOrder rejects configurations that would let Gas2500x take effect inside that window.

Behavior changes (operator-facing)

• --miner.gasprice no longer raises the tx pool minimum gas price: the floor is now a pure function of the chain config gas schedule, and raising it requires scheduling a tier fork. The flag still feeds the miner and the gas price oracle as before.
• eth_simulateV1 non-validation blocks now report BASEFEE = 0 (matching upstream) instead of the old hard-coded 12.5 gwei.
• Localnet enables the fork at block 0, which changes the localnet genesis hash — existing local data directories must be reset.
• Transactions already pending when a tier activates are not swept; they stop being mineable and senders must resubmit at the new price. Admission rejects underpriced transactions one block before the tier fires, keeping the affected set small.

Compatibility

• The fork is unscheduled on mainnet, testnet and devnet: no existing network changes behavior. At the Gas50x tier the derived base fee is identical to the constant it replaces.
• Chain config digest version is bumped to 2; fork ordering rules, backfill definitions and network configs are updated accordingly.

Testing

• New unit tests cover the tier table invariants, fork ordering (including the BASEFEE window rule), txpool admission/promotion/demotion pricing at tier boundaries, the BASEFEE opcode fallback, and the chain config digest golden vectors.
• Verified: params/..., core/txpool/..., core/vm, consensus/misc/eip1559, eth/gasprice, core, internal/ethapi all pass; cmd/XDC builds.

Release notes

• Localnet data directories must be reset, since the genesis hash changes.
• BASEFEE returns 0 in eth_simulateV1 non-validation blocks instead of 12.5 gwei.
• Transactions left pending across a future tier activation must be resubmitted at the new price.

Types of changes

What types of changes does your code introduce to XDC network?
Put an ✅ in the boxes that apply

• build: Changes that affect the build system or external dependencies
• ci: Changes to CI configuration files and scripts
• chore: Changes that don't change source code or tests
• docs: Documentation only changes
• feat: A new feature
• fix: A bug fix
• perf: A code change that improves performance
• refactor: A code change that neither fixes a bug nor adds a feature
• revert: Revert something
• style: Changes that do not affect the meaning of the code
• test: Adding missing tests or correcting existing tests

Impacted Components

Which parts of the codebase does this PR touch?
Put an ✅ in the boxes that apply

• Consensus
• Account
• Network
• Geth
• Smart Contract
• External components
• Not sure (Please specify below)

Checklist

Put an ✅ in the boxes once you have confirmed below actions (or provide reasons on not doing so) that

• This PR has sufficient test coverage (unit/integration test) OR I have provided reason in the PR description for not having test coverage
• Tested on a private network from the genesis block and monitored the chain operating correctly for multiple epochs.
• Provide an end-to-end test plan in the PR description on how to manually test it on the devnet/testnet.
• Tested the backwards compatibility.
• Tested with XDC nodes running this version co-exist with those running the previous version.
• Relevant documentation has been updated as part of this PR
• N/A

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[Copilot]

Pull request overview

Adds the optional Gas2500x gas tier and makes base-fee, TRC21, RPC, and transaction-pool pricing fork-height aware.

Changes:

• Centralizes gas-tier resolution and adds Gas2500x configuration.
• Uses scheduled base fees throughout consensus, RPC, simulation, and txpool paths.
• Updates localnet configuration, compatibility metadata, and tests.

Reviewed changes

Copilot reviewed 40 out of 41 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/state_test_util.go	Replaces removed base-fee constant.
params/gas.go	Implements centralized gas-tier pricing.
params/gas_test.go	Tests tier pricing and value isolation.
params/forks/forks.go	Registers the Gas2500x fork.
params/forks/forks_test.go	Tests fork labels and ordering.
params/config.go	Adds configuration and fork validation.
params/config_test.go	Tests Gas2500x configuration constraints.
params/config_networks.go	Enables Gas2500x on localnet.
params/config_networks_test.go	Verifies network scheduling defaults.
params/config_forks.go	Adds the activation predicate.
params/config_compat_test.go	Updates compatibility-order expectations.
params/config_backfill.go	Integrates compatibility and backfill metadata.
params/config_backfill_test.go	Tests backfill field coverage.
params/config_backfill_generated.go	Adds generated field metadata.
params/config_backfill_fields.json	Declares the new generated field.
internal/ethapi/transaction_args_test.go	Updates mock fork configuration.
internal/ethapi/simulate.go	Corrects simulated base-fee activation.
internal/ethapi/api.go	Prices pending RPC results for the next block.
internal/ethapi/api_test.go	Updates gas-price expectations.
eth/gasprice/gasprice.go	Applies the next-block gas floor.
eth/gasprice/feehistory.go	Calculates scheduled next-block base fees.
core/vm/interpreter.go	Corrects NoBaseFee documentation.
core/vm/instructions_test.go	Tests BASEFEE opcode behavior.
core/vm/evm.go	Corrects EVM context documentation.
core/vm/eips.go	Reads BASEFEE from block context.
core/txpool/validation.go	Validates against the next-block schedule.
core/txpool/validation_mingasprice_test.go	Tests schedule-boundary admission.
core/txpool/validation_denylist_test.go	Uses the immutable gas baseline.
core/txpool/legacypool/legacypool.go	Updates promotion, demotion, and reorg pricing.
core/txpool/legacypool/legacypool_test.go	Tests next-block affordability behavior.
core/state_processor_test.go	Updates test block base-fee construction.
core/genesis.go	Derives genesis base fee from the schedule.
core/genesis_test.go	Tests scheduled genesis pricing.
core/chainconfig_equal.go	Bumps the config digest version.
core/chainconfig_equal_test.go	Updates digest coverage and vectors.
consensus/tests/engine_v2_tests/helper.go	Updates engine-v2 test base fees.
consensus/tests/engine_v1_tests/helper.go	Updates engine-v1 test base fees.
consensus/misc/eip1559/eip1559.go	Makes base-fee calculation block-aware.
consensus/misc/eip1559/eip1559_test.go	Tests scheduled consensus base fees.
common/constants.go	Removes mutable legacy gas constants.
cmd/XDC/config.go	Removes the ineffective pool-floor override.

Files not reviewed (1)

• params/config_backfill_generated.go: Generated file

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[Copilot]

Pull request overview

Copilot reviewed 40 out of 41 changed files in this pull request and generated no new comments.

Files not reviewed (1)

• params/config_backfill_generated.go: Generated file

Suppressed comments (4)

internal/ethapi/api_test.go:4285

• This test does not verify the next-block fork behavior: the mock has no Gas2500x activation, and the expected value is computed with the same helper as production, so using the current height would also pass. Exercise a fork at block 1101 and assert the explicit 2500x value.

	wantGasPrice := new(big.Int).Add(big.NewInt(42), params.BaseFeeForBlock(backend.ChainConfig(), big.NewInt(1101)))

internal/ethapi/simulate.go:165

• The observable simulation change is untested: existing simulate tests contain no base-fee assertions, so a regression could again synthesize a fee in the London-to-EIP1559 window or fail to return zero for non-validation blocks. Add cases for both modes at the EIP-1559 boundary and execute BASEFEE in the simulated call.

	if sim.chainConfig.IsEIP1559(header.Number) {
		// In non-validation mode base fee is set to 0 if it is not overridden.
		// This is because it creates an edge case in EVM where gasPrice < baseFee.
		// Base fee could have been overridden.
		if header.BaseFee == nil {
			if sim.validate {
				header.BaseFee = eip1559.CalcBaseFee(sim.chainConfig, header)

params/config_networks.go:515

• Enabling this fork at genesis changes the localnet genesis hash and makes existing localnet data directories unusable. Add the operator-facing release or migration note requiring a localnet reset; the PR description identifies the impact, but the repository currently has no corresponding documentation change.
  eth/gasprice/feehistory.go:89
• Fee history has comprehensive tests, but they only check the base-fee array length and do not cover this next-block tier transition. Add a case where Gas2500xBlock == bf.blockNumber+1 and assert that the final baseFeePerGas entry is the 2500x price; otherwise an off-by-one regression here remains undetected.

	nextNumber := new(big.Int).SetUint64(bf.blockNumber + 1)
	if chainconfig.IsEIP1559(nextNumber) {
		bf.results.nextBaseFee = eip1559.CalcBaseFeeForBlockNumber(chainconfig, nextNumber)