Dss Flappers

Implementations of MakerDAO surplus auctions, triggered on vow.flap or via new kicker.flap.

Kicker

Implements a Splitter/Flapper calling function that replaces Vow.flap and can be called even when Vat.dai(Vow) < Vat.sin(Vow). The triggering threshold is assumed to be carefully set up and controlled by governance, ensuring there is enough surplus secured (in the Vow based surplus buffer or elsewhere).

Configurable Parameters:

• kbump - Fixed lot size (RAD precision)
• khump - Flap threshold (RAD precision, signed integer value).

Note: It is assumed that the Flop auctions mechanism is disabled and remains in that state. As otherwise it could collide with the above mechanism. Currently this is done through the configuration of Vow.sump as max uint256 (aka infinity).

Note 2: Rate limiting is ensured via the Splitter.

Note 3: Stop functionality is implemented via the Splitter.cage function (reason to leave the Splitter as flapper reference in the Vow and the wards still set). However, even if Vow.cage remains functional, in order to execute End.cage it is still necessary a deep analysis and prior actions in different modules to be executed successfully.

Splitter

Exposes a kick operation to be triggered periodically. Its logic withdraws USDS from the vow and splits it in two parts. The first part (burn) is sent to the underlying flapper contract to be processed by the burn engine. The second part (WAD - burn) is distributed as reward to a farm contract. The kick cadence is determined by the hop value.

Configurable Parameters:

• burn - The percentage of the vow.bump to be moved to the underlying flapper. For example, a value of 0.70 * WAD corresponds to funneling 70% of the USDS to the burn engine.
• hop - Minimum seconds interval between kicks.
• flapper - The underlying burner strategy (e.g. the address of FlapperUniV2SwapOnly).
• farm - The staking rewards contract receiving the rewards.

FlapperUniV2

Exposes an exec operation to be triggered periodically by the Splitter (at a cadence determined by Splitter.hop()). Its logic withdraws USDS from the Splitter and buys gem tokens on Uniswap v2. The acquired tokens, along with a proportional amount of USDS (saved from the initial withdraw) are deposited back into the liquidity pool. Finally, the minted LP tokens are sent to a predefined receiver address.

Configurable Parameters:

• 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.

Note:

• 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 an exec operation to be triggered periodically by the Splitter (at a cadence determined by Splitter.hop()). Its logic withdraws USDS from the Splitter and buys gem tokens on Uniswap v2. The acquired tokens are sent to a predefined receiver address.

Configurable Parameters:

• 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.

SplitterMom

This contract allows bypassing the governance delay when disabling the Splitter 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 USDS is the responsibility of the vow. At the time of a kick, the vow is expected to hold at least the drawn amount (vow.bump) over the configured flapping threshold (vow.hump).