The RTRlib is a lightweight, open-source C library that implements the RPKI/RTR protocol. Basically, it fetches data from an RPKI cache server and allows for prefix origin validation as well as BGP path validation. The RTRlib is the backend for BGP daemons and monitoring tools.
The current version implements RFC 6810, RFC 6811, and draft-ietf-sidr-rpki-rtr-rfc6810-bis-02. The RTRlib is open source and licensed under MIT.