Governance

Motivation

There are many system parameters to control the behavior of the BSC:

• All these parameters of BSC system contracts should be flexible: slashing threshold, cross-chain transfer fees, relayer reward amount and so on.

• params of Staking/Slash/Oracle modules on BC

All these parameters will be determined by BSC Validator Set together through a proposal-vote process based on their staking. Such the process will be carried on BC, and the new parameter values will be picked up by corresponding system contracts via cross-chain communication if needed.

Design Principles

For BC:

• Codebase reuse: Reuse most of the structure of proposal and vote, and the logic about propose and vote.

• Cross chain package Available at once: The cross-chain package should be available once the proposal passed.

• Native params change take place at breath block: The param change of Staking/Slash/Oracle modules on BC take place at breath block after the proposal passed.

For BSC:

• Uniform interface. The contracts who are interested in these parameters only need to implement the same interface.

• Extensible. When adding a new system contract, there is no need to modify any other contracts.

• Failure toleration. Validators could vote to skip false proposals and go on.

• Multiplexing. Now we have only parameters gov, but in the future, there will be more governance functions.

Workflow

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Contract Interface

Every contract that wants to subscribe param change event, should implement the following interface: function updateParam(string key, bytes calldata value) external

Some following check must be done inside the interface:

• The msg sender must be the gov contract.

• Basic check of value. (length, value range)

An example implementation:

modifier onlyGov() {    require(msg.sender == GOV_CONTRACT_ADDR, "the msg sender must be the gov contract");    _;}​function updateParam(string key, bytes calldata value) external onlyGov{    if (key == "relayerReward"){        require(value.length == 32, "the length of value is not 32 when update relayer_reward param");        uint256 memory paramValue = TypesToBytes.ToUint256(0, value);        require(paramValue >= MIN_RELAYER_REWARD, "the relayerReward is smaller than the minimum value");        require(paramValue <= MAX_RELAYER_REWARD, "the relayerReward is bigger than the maximal value");        relayerReward = paramValue；    }else{        require(false, "receive unknown param");    }}

Gov Contract

Implement the cross chain contract interface: handlePackage(bytes calldata msgBytes, bytes calldata proof, uint64 height, uint64 packageSequence)

And do following step: - Basic check. Sequence check, Relayer sender check, block header sync check, merkel proof check. - Check the msg type according to the first byte of msgBytes, only param change msg type supported for now. Check and parse the msg bytes. - Use a fixed gas to invoke the updateParam interface of target contract. Catch any exception and emit fail event if necessary, but let the process go on. - Claim reward for the relayer and increase sequence.

Workflow

Please read this doc to learn how to send transactions on Binance Chain