Submitting a block to Ethereum

Rollup blocks are submitted to the host chain by calling the Zenith submitBlock function, attaching transaction data in a 4844 blob.

Code Flows

These examples assume one has already chosen a set of transactions and bundles, and gotten a co-signature from the Sequencer API.

The builder example has a submission process without host fills that can be referenced for blob construction.

For blocks with host fill components, builders should use a multi-call contract to do the following:

• Call submitBlock as described below

• Pass each permit2 blob to the Passage contract's fillPermit2 method

Creating the blob transaction

1. Transform the SignResponse into a Zenith::BlockHeader.

let header = Zenith::BlockHeader {
    hostBlockNumber: resp.req.host_block_number,
    rollupChainId: U256::from(self.config.ru_chain_id),
    gasLimit: resp.req.gas_limit,
    rewardAddress: resp.req.ru_reward_address,
    blockDataHash: in_progress.contents_hash(),
};

1. Encode the submitBlock transaction data from the BlockHeader & the Sequencer's Signature from the SignResponse

let data = Zenith::submitBlockCall { header, v, r, s, _4: Default::default() }.abi_encode();

NOTE: the final unnamed bytes parameter should be an empty bytes string

1. Encode the transactions into a 4844 blob sidecar containing the rlp-encoded transactions.

pub fn encode_blob(&self) -> SidecarBuilder<SimpleCoder> {
    let mut coder = SidecarBuilder::default();
    coder.ingest(self.encode_raw());
    coder
}

Signet blobs use the alloy SimpleCoder blob encoding scheme. This may change in the future.

1. Attach the blob sidecar to a TransactionRequest.

let tx = TransactionRequest::default().with_blob_sidecar(sidecar).with_input(data);

1. Fill in remaining transaction details (including the calldata, which must contain the encoded submitBlockCall above).

If using a multi-call contract, the input to the multi-call must send the encoded submitBlockCall to the Zenith contract.

1. Submit the constructed transaction to Ethereum.

Note: It is CRITICALLY IMPORTANT to use a private transaction relay to submit blocks coupled with fills. Leaking fill transactions or signed permit2 fills may result in loss of building privileges.