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.

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(),
   };

2. 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();

3. 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
   }

4. Attach the blob sidecar to a TransactionRequest.

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

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

6. Submit the constructed transaction to Ethereum.