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Routers

Maker contracts can be set to utilize a router in order to manage outbound and inbound tokens reserves of offer owners. Routers' interface are constrained by the AbstractRouter contract and use hooks to customize the public functions described below.

modifiers

Function modifier onlyMakers requires that only an approved maker contract can call this functions. Modifier onlyAdmin requires function caller to be the admin of the router. Modifier makerOrAdmin is a disjunction of both the above requirements.

SimpleRouter

The SimpleRouter contract provides a (simple) router instance. We illustrate usage of the main router functions through it.

Liquidity flows

Routers receive requests from approved maker contracts (see gatekeeping). Request can be either to manage inbound (offer taker's payment) or outbound cash flow.

Push request

function push(IERC20 token, address reserve, uint amount) external onlyMakers returns (uint pushed);
  • Input:
    • token is the asset the maker contract wishes to push
    • reserve of the offer owner whose funds are being pushed
    • amount is the amount of asset that should be transferred from the calling maker contract
  • Output: fraction of amount that was successfully pushed to offer owner's reserve.
  • Usage: transfer funds from the maker contracts to an offer owner's reserve. For instance if the reserve is an account on a lender, the router will have a custom push that will take care of calling the proper deposit function.
  • SimpleRouter behavior: transfer funds from msg.sender to reserve. Returns 0 if transfer failed, returns amount otherwise.

Pull request

function pull(IERC20 token, address reserve, uint amount, bool strict) external onlyMakers returns (uint pulled);
  • Input:
    • token is the asset the maker contract wishes to pull
    • reserve of the offer owner where the funds need to be pulled from
    • amount is the amount of asset that should be transferred from reserve to the calling maker contract
  • Output: fraction of amount that was successfully pulled to msg.sender.
  • Usage: transfer funds from an offer owner's reserve to the calling maker contracts. For instance if the reserve is an account on a lender, the router will have a custom pull that will take care of calling the proper redeem function.
  • SimpleRouter behavior: transfer funds from reserve to msg.sender. Returns 0 if transfer failed, returns amount otherwise.

Gatekeeping

Binding a router to a maker contract

function bind(address maker) public onlyAdmin;

Function approves maker as a user of the router. The unbind function can be called to revoke the approval.

Router activation

function activate(IERC20 token) external makersOrAdmin;
  • Usage: performs all router centric approvals that are necessary to route token liquidity. For instance a router using a lender might need to approve the lender for transferring token in deposit calls.
  • SimpleRouter behavior: SimpleRouter does not need to approve any contract, and activate is a no-op in that context.

Router checklist

function checkList(IERC20 token, address reserve) external view;
  • Usage: verifies that the router has performed and received all the necessary approvals to route token liquidity for offer owner's reserve. The function throws with a reason when the first missing approval is detected.
  • SimpleRouter behavior: it verifies that reserve has approved the router for token transfer. Does not throw if offer owner's reserve is the router itself.
Plug and play routing

Since routers are autonomous smart contracts, it is possible to modify an offer logic without redeploying the corresponding maker contracts. The setRouter function of all library based maker contracts can be used to set a new router. By setting a new router for the maker contract, you are indirectly modifying the offer logic of the contract. However the gas requirement of the offer logic is impacted by the router's design. To cope with this, routers provide the routerGaseq() function that returns the amount of gas that is necessary to cover a call to pull and push.

Note that maker contracts' view offerGasreq returns the sum of the offer logic's raw gasreq (without taking router into account) and the router specific gasreq