Based on the conversation from #5 (comment) - this changes innernet's behavior on Linux from automatically falling back to the userspace, instead requiring --backend userspace to be specified.
This should help people avoid weird situations in environments like Docker.
The server now expects a UNIX timestamp after which the invitation will be expired. If a peer invite hasn't been redeemed after it expires, the server will clean up old entries and allow the IP to be re-allocated for a new invite.
Closes#24
This is a stop-gap CSRF protection mechanism from unsophisticated attacks. It's to be considered a temporary solution until a more complete one can be implemented, but it should be sufficient in most cases for the time being.
See https://github.com/tonarino/innernet/issues/38 for further discussion.
Jake McGinty