GPv2Interaction API
The GPv2Interaction library enables settlement contracts to execute arbitrary external contract calls during trading settlements, supporting complex strategies like liquidity sourcing and protocol integrations.
Data Structure
struct Data {
address target;
uint256 value;
bytes callData;
}
| Field | Type | Description |
|---|
target | address | Contract address to call |
value | uint256 | ETH value to send with the call |
callData | bytes | Encoded function call data |
Functions
execute
Performs the actual contract interaction using inline assembly for gas optimization. Propagates revert reasons if calls fail.
function execute(Data calldata interaction) internal {
address target = interaction.target;
uint256 value = interaction.value;
bytes calldata callData = interaction.callData;
// solhint-disable-next-line no-inline-assembly
assembly {
let freeMemoryPointer := mload(0x40)
calldatacopy(freeMemoryPointer, callData.offset, callData.length)
if iszero(
call(gas(), target, value, freeMemoryPointer, callData.length, 0, 0)
) {
returndatacopy(0, 0, returndatasize())
revert(0, returndatasize())
}
}
}
selector
Extracts the 4-byte function selector from calldata for event logging.
function selector(Data calldata interaction) internal pure returns (bytes4);
Settlement Integration
Interactions run at three distinct phases:
| Phase | Stage | Common Use Cases |
|---|
| Pre-settlement | interactions[0] | Approvals, permits, token wrapping |
| Intra-settlement | interactions[1] | DEX swaps, liquidity sourcing |
| Post-settlement | interactions[2] | Token unwrapping, fee distribution |
Common Use Cases
- DEX swaps for liquidity sourcing (Uniswap, Balancer, Curve)
- Token wrapping/unwrapping (WETH)
- Approval grants to external protocols
- Trade routing through aggregators like 1inch
- EIP-2612 permit calls for gasless approvals
Security
Interactions cannot target the vaultRelayer contract. Only authorized solvers may submit settlements with interactions. Reentrancy guards prevent attack vectors. Misbehaving solvers face financial penalties.
Best Practices
- Order interactions by settlement phase carefully
- Ensure all calls succeed (failures cause the entire settlement to revert)
- Use type-safe encoding methods (e.g.,
abi.encodeWithSelector) rather than manual byte manipulation
