SwapRouter

Overview

The SwapRouter is a Venus periphery contract that enables users to swap tokens and interact with Venus markets in a single transaction. It supports both ERC-20 and native tokens (e.g., BNB), allowing users to supply or repay Venus markets seamlessly after a swap. This contract is designed for composability, security, and gas efficiency.

Prerequisites

Before using the SwapRouter, users should:

Approve the SwapRouter to spend their tokens (for ERC-20 operations).
Ensure the target vToken market is listed in the Venus Comptroller.
For native token operations, send the appropriate value with the transaction.

Inheritance

Ownable2StepUpgradeable — Two-step ownership transfer pattern
ReentrancyGuardUpgradeable — Reentrancy protection

Immutable State Variables

NATIVE_TOKEN_ADDR: Address representing the native token (e.g., BNB)
COMPTROLLER: Venus Comptroller contract for market validation
SWAP_HELPER: SwapHelper contract for executing swaps
WRAPPED_NATIVE: Wrapped native token contract (e.g., WBNB)
NATIVE_VTOKEN: vToken contract for the native token (e.g., vBNB)

Architecture

┌───────────────────────────────────────────────┐
│                Venus Core Protocol           │
│  ┌───────────┐  ┌──────────┐                │
│  │Comptroller│  │  vTokens │                │
│  └─────┬─────┘  └────┬─────┘                │
└────────┼─────────────┼───────────────────────┘
         │             │
         ▼             ▼
┌───────────────────────────────────────────────┐
│                SwapRouter                    │
│  - Swaps tokens via SwapHelper               │
│  - Supplies or repays Venus markets          │
│  - Handles native and ERC-20 tokens          │
└───────────────┬──────────────────────────────┘
                │
                ▼
┌───────────────────────────────────────────────┐
│                SwapHelper                     │
│  - Executes authorized swaps                  │
│  - Interacts with DEX protocols               │
└───────────────────────────────────────────────┘

Solidity API

swapAndSupply

Swaps an input token for the underlying asset of a Venus market and supplies it on behalf of the user.

function swapAndSupply(
    address vToken,
    address tokenIn,
    uint256 amountIn,
    uint256 minAmountOut,
    bytes calldata swapCallData
) external

Parameters:

vToken: The vToken market to supply to
tokenIn: The input token to swap from
amountIn: The amount of input tokens to swap
minAmountOut: The minimum amount of output tokens expected
swapCallData: Encoded swap instructions for SwapHelper

Scenario Example: User wants to supply 1,000 USDC to a Venus market using DAI:

User holds 1,000 DAI.
Calls swapAndSupply with vUSDC, DAI, 1,000 DAI, minAmountOut = 995 USDC, and swapCallData for DAI→USDC swap.
SwapRouter swaps 1,000 DAI → ~998 USDC.
Supplies ~998 USDC to vUSDC market.
Final: User has ~998 USDC supplied, 0 DAI, receives vUSDC tokens.

Events:

SwapAndSupply

Errors:

ZeroAmount: Thrown if amountIn is zero.
ZeroAddress: Thrown if vToken or tokenIn is zero address.
MarketNotListed: Thrown if vToken is not listed in Comptroller.
InsufficientBalance: Thrown if user has insufficient balance for swap.
SwapFailed: Thrown if swap operation fails.
InsufficientAmountOut: Thrown if received amount is less than minAmountOut.
NoTokensReceived: Thrown if no tokens are received from swap.
SupplyFailed: Thrown if supply to Venus market fails (returns error code).

swapNativeAndSupply

Swaps native tokens (e.g., BNB) for the underlying asset and supplies it to a Venus market.

function swapNativeAndSupply(
    address vToken,
    uint256 minAmountOut,
    bytes calldata swapCallData
) external payable

Parameters:

vToken: The vToken market to supply to
minAmountOut: The minimum amount of output tokens expected
swapCallData: Encoded swap instructions for SwapHelper

Scenario Example:

User wants to supply 2 BNB to a Venus market using native BNB:

User holds 2 BNB.
Calls swapNativeAndSupply with vUSDT, minAmountOut = 600 USDT, and swapCallData for BNB→USDT swap, sending 2 BNB.
SwapRouter wraps 2 BNB to WBNB, swaps WBNB → ~610 USDT.
Supplies ~610 USDT to vUSDT market.
Final: User has ~610 USDT supplied, 0 BNB, receives vUSDT tokens.

Events:

SwapAndSupply

Errors:

ZeroAmount: Thrown if msg.value is zero.
ZeroAddress: Thrown if vToken is zero address.
MarketNotListed: Thrown if vToken is not listed in Comptroller.
SwapFailed: Thrown if swap operation fails.
InsufficientAmountOut: Thrown if received amount is less than minAmountOut.
NoTokensReceived: Thrown if no tokens are received from swap.
SupplyFailed: Thrown if supply to Venus market fails.

swapAndRepay

Swaps an input token and repays the user's debt in a Venus market.

function swapAndRepay(
    address vToken,
    address tokenIn,
    uint256 amountIn,
    uint256 minAmountOut,
    bytes calldata swapCallData
) external

Parameters:

vToken: The vToken market to repay debt to
tokenIn: The input token to swap from
amountIn: The amount of input tokens to swap
minAmountOut: The minimum amount of output tokens expected
swapCallData: Encoded swap instructions for SwapHelper

Scenario Example: User has 500 USDT debt in a Venus market and wants to repay using USDC:

User holds 510 USDC.
Calls swapAndRepay with vUSDT, USDC, 510 USDC, minAmountOut = 500 USDT, and swapCallData for USDC→USDT swap.
SwapRouter swaps 510 USDC → ~505 USDT.
Repays 500 USDT debt in vUSDT market.
Final: User has 0 USDT debt, 5 USDT returned as excess, 0 USDC.

Events:

SwapAndRepay

Errors:

ZeroAmount: Thrown if amountIn or user debt is zero.
ZeroAddress: Thrown if vToken or tokenIn is zero address.
MarketNotListed: Thrown if vToken is not listed in Comptroller.
InsufficientBalance: Thrown if user has insufficient balance for swap.
SwapFailed: Thrown if swap operation fails.
InsufficientAmountOut: Thrown if received amount is less than minAmountOut.
NoTokensReceived: Thrown if no tokens are received from swap.
RepayFailed: Thrown if repay to Venus market fails (returns error code).

swapNativeAndRepay

Swaps native tokens and repays the user's debt in a Venus market.

function swapNativeAndRepay(
    address vToken,
    uint256 minAmountOut,
    bytes calldata swapCallData
) external payable

Parameters:

vToken: The vToken market to repay debt to
minAmountOut: The minimum amount of output tokens expected
swapCallData: Encoded swap instructions for SwapHelper

Scenario Example: User has 0.5 BNB debt in a Venus market and wants to repay using native BNB:

User holds 0.5 BNB.
Calls swapNativeAndRepay with vDAI, minAmountOut = 1,000 DAI, and swapCallData for BNB→DAI swap, sending 0.5 BNB.
SwapRouter wraps 0.5 BNB to WBNB, swaps WBNB. → ~1,010 DAI.
Repays 1,000 DAI debt in vDAI market.
Final: User has 0 DAI debt, 10 DAI returned as excess, 0 ETH.

Events:

SwapAndRepay

Errors:

ZeroAmount: Thrown if msg.value or user debt is zero.
ZeroAddress: Thrown if vToken is zero address.
MarketNotListed: Thrown if vToken is not listed in Comptroller.
SwapFailed: Thrown if swap operation fails.
InsufficientAmountOut: Thrown if received amount is less than minAmountOut.
NoTokensReceived: Thrown if no tokens are received from swap.
RepayFailed: Thrown if repay to Venus market fails.

swapAndRepayFull

Swaps tokens to repay the user's full debt in a Venus market.

function swapAndRepayFull(
    address vToken,
    address tokenIn,
    uint256 maxAmountIn,
    bytes calldata swapCallData
) external

Parameters:

vToken: The vToken market to repay full debt to
tokenIn: The input token to swap from
maxAmountIn: The maximum amount of input tokens to use
swapCallData: Encoded swap instructions for SwapHelper

Scenario Example: User has 1,200 USDC debt in a Venus market and wants to repay full debt using DAI:

User holds 1,250 DAI.
Calls swapAndRepayFull with vUSDC, DAI, 1,250 DAI, and swapCallData for DAI→USDC swap.
SwapRouter swaps 1,250 DAI → ~1,210 USDC.
Repays 1,200 USDC debt in vUSDC market.
Final: User has 0 USDC debt, 10 USDC returned as excess, 0 DAI.

Events:

SwapAndRepay

Errors:

ZeroAmount: Thrown if maxAmountIn or user debt is zero.
ZeroAddress: Thrown if vToken or tokenIn is zero address.
MarketNotListed: Thrown if vToken is not listed in Comptroller.
InsufficientBalance: Thrown if user has insufficient balance for swap.
SwapFailed: Thrown if swap operation fails.
InsufficientAmountOut: Thrown if received amount is less than debt amount.
NoTokensReceived: Thrown if no tokens are received from swap.
RepayFailed: Thrown if repay to Venus market fails.

swapNativeAndRepayFull

Swaps native tokens to repay the user's full debt in a Venus market.

function swapNativeAndRepayFull(
    address vToken,
    bytes calldata swapCallData
) external payable

Parameters:

vToken: The vToken market to repay full debt to
swapCallData: Encoded swap instructions for SwapHelper

Scenario Example: User has 0.8 BNB debt in a Venus market and wants to repay full debt using native BNB:

User holds 0.85 BNB.
Calls swapNativeAndRepayFull with vUSDT and swapCallData for BNB→USDT swap, sending 0.85 BNB.
SwapRouter wraps 0.85 BNB to WBNB, swaps WBNB → ~260 USDT.
Repays 250 USDT debt in vUSDT market.
Final: User has 0 USDT debt, 10 USDT returned as excess, 0 BNB.

Events:

SwapAndRepay

Errors:

ZeroAmount: Thrown if msg.value or user debt is zero.
ZeroAddress: Thrown if vToken is zero address.
MarketNotListed: Thrown if vToken is not listed in Comptroller.
SwapFailed: Thrown if swap operation fails.
InsufficientAmountOut: Thrown if received amount is less than debt amount.
NoTokensReceived: Thrown if no tokens are received from swap.
RepayFailed: Thrown if repay to Venus market fails.

sweepToken

Allows the contract owner to recover leftover ERC-20 tokens from the contract.

function sweepToken(IERC20Upgradeable token) external onlyOwner

Example:

swapRouter.sweepToken(tokenAddress);

sweepNative

Allows the contract owner to recover leftover native tokens from the contract.

function sweepNative() external onlyOwner

Example:

swapRouter.sweepNative();

Error Definitions

ZeroAddress(): Thrown when a zero address is provided for required parameters.
ZeroAmount(): Thrown when a zero amount is provided for required parameters or user debt is zero.
SupplyFailed(uint256 errorCode): Thrown when supply operation to Venus market fails. Returns the error code from the vToken.
RepayFailed(uint256 errorCode): Thrown when repay operation to Venus market fails. Returns the error code from the vToken.
SwapFailed(): Thrown when the swap operation fails (e.g., SwapHelper call reverts).
NoTokensReceived(): Thrown when no tokens are received from the swap operation.
NativeTransferFailed(): Thrown when native token transfer fails (e.g., sweepNative fails to send ETH/BNB).
InsufficientBalance(): Thrown when the user has insufficient balance for the swap or supply/repay operation.
MarketNotListed(address vToken): Thrown when the vToken market is not listed in the Comptroller.
InsufficientAmountOut(uint256 amountOut, uint256 minAmountOut): Thrown when the swap output is less than the minimum required amount (slippage protection).
UnauthorizedNativeSender(address sender): Thrown when an unauthorized sender tries to send native tokens to the contract.

Security Considerations

Access Control

Only the contract owner can sweep tokens or native currency.
All swap/supply/repay functions are open to users, but require proper approvals and market listing.

Reentrancy Protection

All external functions are protected by the nonReentrant modifier.

Slippage Protection

All swap functions require a minAmountOut parameter. The transaction reverts if the swap output is below this threshold.

Market Validation

The contract checks that the vToken market is listed in the Comptroller before proceeding.

Account Safety

The contract validates user balances and market status before executing operations.

Dust Handling

Any excess tokens after repay operations are returned to the user.

Integration

For Users

Approve the SwapRouter to spend your tokens (for ERC-20 operations):
```
IERC20(tokenIn).approve(swapRouterAddress, amount);
```
Call the desired function (swapAndSupply, swapAndRepay, etc.) with the appropriate parameters and swapCallData.
For native token operations, send the required value with your transaction.
Monitor events (SwapAndSupply, SwapAndRepay) for transaction status.

For Developers

Swap API Integration

Cross-asset operations require signed swap data from the Venus Swap API:

Request a swap quote from the API with source and destination tokens
Receive encoded multicall parameters with backend signature
Pass the signed _swapData to the entry function

Audits

SwapRouter undergoes security audits before mainnet deployment. Audit reports are available in the venus-periphery repository.

Deployment

See Deployed Contracts for current addresses.

Last updated 17 days ago

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Overview

Prerequisites

Inheritance

Immutable State Variables

Architecture

Solidity API

swapAndSupply

swapNativeAndSupply

swapAndRepay

swapNativeAndRepay

swapAndRepayFull

swapNativeAndRepayFull

sweepToken

sweepNative

Error Definitions

Security Considerations

Access Control

Reentrancy Protection

Slippage Protection

Market Validation

Account Safety

Dust Handling

Integration

For Users

For Developers

Swap API Integration

Audits

Deployment