Dss Flappers

Implementations of MakerDao surplus auctions, triggered on vow.flap. The current featured Flapper is FlapperUniV2.

FlapperUniV2

Exposes a kick operation to be triggered periodically. Its logic withdraws DAI from the vow and buys gem tokens on Uniswap v2. The acquired tokens, along with a proportional amount of additional DAI withdrawn from the vow, are deposited back into the liquidity pool. Finally, the minted LP tokens are sent to a predefined receiver address.

Configurable Parameters:

• hop - Minimum seconds interval between kicks.
• pip - A reference price oracle, used for bounding the exchange rate of the swap.
• want - Relative multiplier of the reference price to insist on in the swap. For example, a value of 0.98 * WAD allows for a 2% worse price than the reference.

Notes:

• As a kick operation also withdraws DAI for depositing in the pool (and not only for swapping), it can in practice reduce the Surplus Buffer to below vow.bump.

• Although the Flapper interface is conformant with the Emergency Shutdown procedure and will stop operating when it is triggered, LP tokens already sent to the receiver do not have special redeeming handling. Therefore, in case the Pause Proxy is the receiver and governance does not control it, the LP tokens can be lost or seized by a governance attack.

FlapperUniV2SwapOnly

Exposes a kick operation to be triggered periodically. Its logic withdraws DAI from the vow and buys gem tokens on Uniswap v2. The acquired tokens are sent to a predefined receiver address.

Configurable Parameters:

• hop - Minimum seconds interval between kicks.
• pip - A reference price oracle, used for bounding the exchange rate of the swap.
• want - Relative multiplier of the reference price to insist on in the swap. For example, a value of 0.98 * WAD allows for a 2% worse price than the reference.

FlapperMom

This contract allows bypassing the governance delay when disabling the Flapper in an emergency.

OracleWrapper

Allows for scaling down an oracle price by a certain value. This can be useful when the gem is a redenominated version of an existing token, which already has a reliable oracle.

General Note:

• Availability and accounting of the withdrawn DAI is the responsibility of the vow. At the time of a kick, the vow is expected to hold at least the swapped amount (vow.bump) over the configured flapping threshold (vow.hump).