openzeppelin-contracts/contracts/GSN

= Gas Station Network (GSN)

This set of contracts provide all the tools required to make a contract callable via the https://gsn.openzeppelin.com[Gas Station Network].

TIP: If you're new to the GSN, head over to our xref:openzeppelin::gsn/what-is-the-gsn.adoc[overview of the system] and basic guide to xref:ROOT:gsn.adoc[creating a GSN-capable contract].

The core contract a recipient must inherit from is {GSNRecipient}: it includes all necessary interfaces, as well as some helper methods to make interacting with the GSN easier.

Utilities to make writing xref:ROOT:gsn-bouncers.adoc[GSN Bouncers] easy are available in {GSNBouncerBase}, or you can simply use one of our pre-made bouncers:

* {GSNBouncerERC20Fee} charges the end user for gas costs in an application-specific xref:ROOT:tokens.adoc#ERC20[ERC20 token]
* {GSNBouncerSignature} accepts all relayed calls that have been signed by a trusted third party (e.g. a private key in a backend)

You can also take a look at the two contract interfaces that make up the GSN protocol: {IRelayRecipient} and {IRelayHub}, but you won't need to use those directly.

NOTE: This feature is being released in the next version of OpenZeppelin Contracts, available right now through `npm install @openzeppelin/contracts@next`.

== Recipient

{{GSNRecipient}}

== Bouncers

{{GSNBouncerBase}}
{{GSNBouncerERC20Fee}}
{{GSNBouncerSignature}}

== Protocol

{{IRelayRecipient}}
{{IRelayHub}}