https://github.com/apple/darwin-xnu/tree/master/bsd
Also, more recently they imported pf from OpenBSD:
https://github.com/apple/darwin-xnu/blob/master/bsd/net/pf.c
Or do you mean that they have recently taken more code from other BSDs than FreeBSD?
The POSIX network stack for example, is now deprecated, and one must use Network.framework for the more up to date features,
"Introducing Network.framework: A modern alternative to Sockets"
https://developer.apple.com/videos/play/wwdc2018/715/
"Optimizing Your App for Today’s Internet"
https://developer.apple.com/videos/play/wwdc2018/714/
Likewise the long term roadmap introduced in Catalina plans to turn macOS into a micro-kernel, by moving all kernel extensions into userspace drivers.
The POSIX network stack for example, is now deprecated, and one must use Network.framework for the more up to date features,
"Introducing Network.framework: A modern alternative to Sockets"
https://developer.apple.com/videos/play/wwdc2018/715/
"Optimizing Your App for Today’s Internet"
https://developer.apple.com/videos/play/wwdc2018/714/
Likewise the long term roadmap introduced in Catalina plans to turn macOS into a micro-kernel, by moving all kernel extensions into userspace drivers.