Extended RPC Method Support and Block Payload Enhancement to enable fork testing

[blockketten]

Background

Tron’s VM supports most of the features of modern solidity and it would be possible for us to build products on Tron in a similar fashion to what we do on EVM chains but most modern development tools do not work with Tron. Most of the differences lay at the RPC level, making it very hard to run core security tests (fork tests are not possible using Foundry, just basic forks do not work either)

Forking is a hard technical requirement for us, we need to be able to perform tests on our contracts with live state to ensure things are working properly. Currently we haven’t found any solution to get a fork (even tenderly has no support for tron unfortunately), so we tried to perform these manually using anvil / forge.

We found that Foundry is unable to perform the fork tests due to some diffs in the returned payload by the json RPCs.

Methods required to fork

By running fork tests on eth mainnet behind a proxy, we identified most of the methods required to perform them

eth_chainId
eth_gasPrice
eth_getBlockByNumber
eth_getStorageAt
eth_getBalance
eth_getTransactionCount
eth_getCode
eth_blockNumber

Unfortunately, Foundry is unable to work with Tron’s RPCs, as unmarshalling data returned by the endpoint fails.

anvil --fork-url https://powerful-polished-gas.tron-mainnet.quiknode.pro/xxx/jsonrpc

Error: failed to get fork block number

Caused by:
   0: deserialization error: Invalid string length at line 1 column 26801
   1: Invalid string length at line 1 column 26801

Location:
    /Users/runner/work/foundry/foundry/crates/anvil/src/config.rs:1154:18

Probable root cause

After some digging, we identified the possible root cause for this. The block payload from the tron rpc is lacking the stateRoot field content, which is always equal to 0x

This single field could be the only reason why some of the Foundry tools are not working properly and crashing whenever some block payloads are deserialized.

curl --location 'https://api.trongrid.io/jsonrpc' --header 'Content-Type:application/json' --data '{
    "jsonrpc": "2.0",
    "method": "eth_getBlockByNumber",
    "params": ["latest", true],
    "id": 1
}' | jq .result

{
  "baseFeePerGas": "0x0",
  "difficulty": "0x0",
  "extraData": "0x",
  "gasLimit": "0x160227b88",
  "gasUsed": "0x360d92",
  "hash": "0x00000000040a0687e0fc7194aabd024a4786ce94ad63855774f8d48896d8750b",
  "logsBloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
  "miner": "0x9a96c8003a1e3a6866c08acff9f629e2a6ef062b",
  "mixHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
  "nonce": "0x0000000000000000",
  "number": "0x40a0687",
  "parentHash": "0x00000000040a068652c581a982a0d17976201ad44aa28eb4e24881e82f99ee04",
  "receiptsRoot": "0x0000000000000000000000000000000000000000000000000000000000000000",
  "sha3Uncles": "0x0000000000000000000000000000000000000000000000000000000000000000",
  "size": "0xba05",
  "stateRoot": "0x", // foundry is probably expecting a bytes32 here
  "timestamp": "0x6759f2f1",
  "totalDifficulty": "0x0",
  "transactions": [...]
}

Mocking the stateRoot

To move further in our testing, we used mitmproxy to proxy all requests made to the RPC and manually mock the stateRoot in the eth_getBlockByNumber queries. We now hit another issue

anvil --fork-url http://localhost:8080
Error: failed to create genesis

Caused by:
    failed to get account for 0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266: server returned an error response: error code -32601: the method eth_getTransactionCount does not exist/is not available, data: "{}"

Location:
    /Users/runner/work/foundry/foundry/crates/anvil/src/eth/backend/mem/mod.rs:345:39

The eth_getTransactionCount is not defined on the tron RPC.

Mocking the transaction count result

Next step is now to intercept eth_getTransactionCount methods and return a mocked value. We hit another core issue when the eth_getCode query is made

anvil --fork-url http://localhost:8080
Error: failed to create genesis

Caused by:
    failed to get account for 0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266: server returned an error response: error code -32602: QUANTITY not supported, just support TAG as latest, data: "{}"

Location:
    /Users/runner/work/foundry/foundry/crates/anvil/src/eth/backend/mem/mod.rs:345:39

When replaying these queries manually, we can see that the method is unable to support arbitrary block tag values for the getCode query (only supports latest )

curl --location https://powerful-polished-gas.tron-mainnet.quiknode.pro/xxx/jsonrpc --header 'Content-Type:application/json' --data '{
    "jsonrpc": "2.0",
    "method": "eth_getCode",
    "params": ["0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266", "0x1234"],
    "id": 1
}'
{"jsonrpc":"2.0","id":1,"error":{"code":-32602,"message":"QUANTITY not supported, just support TAG as latest","data":"{}"}}

Deep state management issue

It seems that most issues are coming from the ability for the tron rpc nodes to retrieve state specific data. First, the inability to provide a stateRoot in the block body shows that there might be a completely different state handling from what the evm chains are used to do.

Same thing for eth_getCode where we are completely unable to retrieve anything that is not at the tip of the chain.

Rationale

Fork testing is essential for secure smart contract development as, it allows testing contracts against live network state. Currently, industry-standard tools like Foundry cannot perform fork tests on Tron due to RPC limitations, limiting the ecosystem development of Tron.

Use cases:

• Security testing of smart contracts against production state
• Integration testing with existing protocols
• Local development environment that mirrors mainnet
• Automated testing pipelines

Specification

The following features are requested in the RPC implementation for Tron:

Block Payload Enhancement

• Add proper stateRoot field in block responses (currently returns "0x")

Extended RPC Method Support

• Implement full eth_getTransactionCount functionality
• Add support for arbitrary block tags in eth_getCode (currently only supports "latest")

Test Specification

Success criteria:

1. Foundry's anvil should successfully fork Tron mainnet
2. Fork tests should execute without deserialization errors
3. Historical state queries should return accurate data

Scope Of Impact

• Smart contract development workflows
• Testing frameworks and tools
• Security audit processes

Implementation

The Kiln team is willing to help test and provide feedback during implementation.

[simbadMarino]

Hello Kiln team, thanks!

tronprotocol devs: Please help us supporting Kiln on this feature as this is a roadblock for several enterprise-grade platforms to enable TRON Staking capabilities like Fireblocks, Ledger Enterprise, VanEck, TRUST, etc .

Let's discuss potential solutions and what would be the best to increase TRON interoperability further :)

[DongDongSunny]

@simbadMarino could you explain more of the feature that you want Tron to support?

[317787106]

@blockketten Let's discuss the eth_getBlockByNumber API. Since TRON does not have a stateRoot, we currently set its value to "0x". Would you prefer extending it to "0x000...0" (a 32-byte length value)? This change might impact other developers as well.

[317787106]

@blockketten In Ethereum JSON-RPC, the method eth_getTransactionCount refers to the total transaction count of a specific owner address. However, due to the limitations of TRON's data structure, we are unable to calculate this for each address in real-time. As a result, this method is not supported.

What are your suggestions for addressing this limitation?

[Federico2014]

@blockketten Thank you for your suggestions. We will consider implementing Tron's Mainnet forking testing tool. It is quite necessary.

[317787106]

@blockketten Let's discuss the eth_getCode API. Since TRON does not maintain a state trie, we can only query data from the latest database. When a specific block number (i.e., QUANTITY) is specified, it refers to historical data, which we are unable to query. This limitation applies to all other APIs as well.

[blockketten]

Thank you for your answers, @317787106 and @Federico2014! In the Tron developer docs, it states that Tron does maintain a state trie. Can you clarify what you mean when you say that it does not maintain a state trie? Also, what are the precise limitations of the Tron data structure that prevent real time accounting of address transaction counts?

@Federico2014 Do you mean that you will implement forking functionality into TronBox? If so, how can we track progress on this?

[317787106]

@blockketten The column accountStateRoot in BlockHeader is empty now. We don't have an index of user-initiated transactions in leveldb, so it's impossible to calculate the amount, you can only get it from Tronscan.

[Federico2014]

@blockketten We plan to implement this fork function first through command line tools to confirm its feasibility. After that, we will communicate with the Tronbox team to support this function. However, it is still in the early stages. After we sort out the relevant information recently, we will make a schedule, and update the progress on the issues of the java-tron ​​project.

[simbadMarino]

@Federico2014 is there an ETA for at least a Beta release of the fork function so Kiln and other teams can begin testing?

[Federico2014]

@simbadMarino We will try our best to make the fork CLI tool available in the next release of java-tron. The specific date is not confirmed yet.

[simbadMarino]

Thanks @Federico2014 ! This will greatly increase TRON's interoperability. Kudos to the team for prioritizing this feature! :) Happy New Year, everyone!

[angrynurd]

To support fork testing, does Tron require significant architectural changes, and how will these changes impact the existing Tron network and smart contracts?

[Federico2014]

@endiaoekoe It doesn't require architectural changes. We will add the fork tool in the Toolkit, which does not influence the existing Tron network and smart contracts.