By leveraging an efficient command-based structure, users can execute a wide variety of actions such as token swaps, NFT transfers, and ERC-20 payments, all within one call. Each operation is executed based on its corresponding bytes1 identifier, which the router decodes and processes.
However, this flexibility introduces potential side-effects when certain operations do not fully consume the provided input tokens.
Specifically, if a swap operation does not consume the full input amount, the leftover tokens remain in the UniversalRouter contract.
The UniversalRouter processes operations by interpreting a series of commands, where each command is represented by a bytes1 identifier. The router loops through the provided commands, executes the corresponding logic, and passes along outputs where necessary.
Each command corresponds to a specific operation, such as:
Uniswap V2 and V3 swaps (e.g., V3_SWAP_EXACT_IN or V2_SWAP_EXACT_OUT).
ERC-20 or NFT transfers.
Permit2 transfers.
Wrapping or unwrapping ETH.
Other payment or NFT-related operations.
The Problem: Leftover Input Amount After a Swap
One common issue arises in scenarios where a swap operation does not fully consume the input tokens. For instance, when executing a swap using the V3_SWAP_EXACT_OUT command, the contract might only consume a portion of the input amount (depending on liquidity and the trade path), leaving the leftover tokens sitting in the UniversalRouter.
These leftover funds can remain unclaimed and may potentially be lost if not addressed properly.
Issues with the Uniswap UniversalRouter in Scenarios of Incorrect Operations
The Uniswap UniversalRouter is a powerful contract that allows users to batch multiple operations into a single transaction. By leveraging an efficient command-based structure, users can execute a wide variety of actions such as token swaps, NFT transfers, and ERC-20 payments, all within one call. Each operation is executed based on its corresponding bytes1 identifier, which the router decodes and processes.
However, this flexibility introduces potential pitfalls when certain operations do not fully consume the provided input tokens. Specifically, if a swap operation does not consume the full input amount, the leftover tokens remain in the UniversalRouter contract, which can lead to unintended outcomes.
How the UniversalRouter Works
The UniversalRouter processes operations by interpreting a series of commands, where each command is represented by a bytes1 identifier. The router loops through the provided commands, executes the corresponding logic, and passes along outputs where necessary.
Each command corresponds to a specific operation, such as:
Uniswap V2 and V3 swaps (e.g., V3_SWAP_EXACT_IN or V2_SWAP_EXACT_OUT).
ERC-20 or NFT transfers.
Permit2 transfers.
Wrapping or unwrapping ETH.
Other payment or NFT-related operations.
A user can bundle these commands together in a single transaction. For example, one could execute a Uniswap V3 swap and then immediately transfer the swapped tokens to a recipient.
The Problem: Leftover Input Amount After a Swap
One common issue arises in scenarios where a swap operation does not fully consume the input tokens. For instance, when executing a swap using the V3_SWAP_EXACT_IN command, the contract might only consume a portion of the input amount (depending on liquidity and the trade path), leaving the leftover tokens sitting in the UniversalRouter.
Example Scenario: Leftover Tokens in UniversalRouter
Consider the following operation flow:
V3 Swap (Exact Input): The user provides 1 ETH to be swapped for USDC, but only 0.8 ETH is needed to fulfill the swap (due to price slippage or liquidity constraints).
Result: The swap is successful, and the user receives USDC, but 0.2 ETH remains in the UniversalRouter contract.
In this case, the user might not even be aware that 0.2 ETH is left in the contract. These leftover funds can remain unclaimed and may potentially be lost if not addressed properly.
Solution: Attach a SWEEP Call After Each Operation
To ensure that any leftover tokens are properly handled, it is recommended to always attach a SWEEP call after operations that involve transferring tokens (e.g., swaps, payments). The SWEEP command allows the contract to transfer any remaining tokens from the router contract to a specified recipient, ensuring that no tokens are left behind.
However, this flexibility introduces potential side-effects when certain operations do not fully consume the provided input tokens.
Specifically, if a swap operation does not consume the full input amount, the leftover tokens remain in the UniversalRouter contract.
The UniversalRouter processes operations by interpreting a series of commands, where each command is represented by a bytes1 identifier. The router loops through the provided commands, executes the corresponding logic, and passes along outputs where necessary.
Each command corresponds to a specific operation, such as:
Uniswap V2 and V3 swaps (e.g., V3_SWAP_EXACT_IN or V2_SWAP_EXACT_OUT).
ERC-20 or NFT transfers.
Permit2 transfers.
Wrapping or unwrapping ETH.
Other payment or NFT-related operations.
The Problem: Leftover Input Amount After a Swap
One common issue arises in scenarios where a swap operation does not fully consume the input tokens. For instance, when executing a swap using the V3_SWAP_EXACT_OUT command, the contract might only consume a portion of the input amount (depending on liquidity and the trade path), leaving the leftover tokens sitting in the UniversalRouter.
These leftover funds can remain unclaimed and may potentially be lost if not addressed properly.
Issues with the Uniswap UniversalRouter in Scenarios of Incorrect Operations
The Uniswap UniversalRouter is a powerful contract that allows users to batch multiple operations into a single transaction. By leveraging an efficient command-based structure, users can execute a wide variety of actions such as token swaps, NFT transfers, and ERC-20 payments, all within one call. Each operation is executed based on its corresponding bytes1 identifier, which the router decodes and processes.
However, this flexibility introduces potential pitfalls when certain operations do not fully consume the provided input tokens. Specifically, if a swap operation does not consume the full input amount, the leftover tokens remain in the UniversalRouter contract, which can lead to unintended outcomes.
How the UniversalRouter Works
The UniversalRouter processes operations by interpreting a series of commands, where each command is represented by a bytes1 identifier. The router loops through the provided commands, executes the corresponding logic, and passes along outputs where necessary.
Each command corresponds to a specific operation, such as:
Uniswap V2 and V3 swaps (e.g., V3_SWAP_EXACT_IN or V2_SWAP_EXACT_OUT).
ERC-20 or NFT transfers.
Permit2 transfers.
Wrapping or unwrapping ETH.
Other payment or NFT-related operations.
A user can bundle these commands together in a single transaction. For example, one could execute a Uniswap V3 swap and then immediately transfer the swapped tokens to a recipient.
The Problem: Leftover Input Amount After a Swap
One common issue arises in scenarios where a swap operation does not fully consume the input tokens. For instance, when executing a swap using the V3_SWAP_EXACT_IN command, the contract might only consume a portion of the input amount (depending on liquidity and the trade path), leaving the leftover tokens sitting in the UniversalRouter.
Example Scenario: Leftover Tokens in UniversalRouter
Consider the following operation flow:
V3 Swap (Exact Input): The user provides 1 ETH to be swapped for USDC, but only 0.8 ETH is needed to fulfill the swap (due to price slippage or liquidity constraints).
Result: The swap is successful, and the user receives USDC, but 0.2 ETH remains in the UniversalRouter contract.
In this case, the user might not even be aware that 0.2 ETH is left in the contract. These leftover funds can remain unclaimed and may potentially be lost if not addressed properly.
Solution: Attach a SWEEP Call After Each Operation
To ensure that any leftover tokens are properly handled, it is recommended to always attach a SWEEP call after operations that involve transferring tokens (e.g., swaps, payments). The SWEEP command allows the contract to transfer any remaining tokens from the router contract to a specified recipient, ensuring that no tokens are left behind.
