pcap_free_datalinks(3) on FreeBSD
The text 081a2b7dd837, as FreeBSD 13.4-RELEASE, FreeBSD 13.3-RELEASE, FreeBSD 13.2-RELEASE, FreeBSD 13.1-RELEASE, FreeBSD 13.0-RELEASE, FreeBSD 12.4-RELEASE, FreeBSD 12.3-RELEASE, FreeBSD 12.2-RELEASE, FreeBSD 11.4-RELEASE shipped it.
get a list of link-layer header types supported by a capture device, and free that list