BSD uses the KAME stack to implement the IPv6 networking protocols. KAME is the leading IPv6 stack and has been integrated into BSD/OS, FreeBSD, NetBSD and OpenBSD since 2000, so your BSD system should have it unless you run a very old version of BSD. IPv6 will eventually replace the current internet protocol, IPv4. When you switch from IPv4 to IPv6, then BSD will be ready.