This job posting for Facebook is what references Facebook's interest in making the network stack match or beat FreeBSD's implementation. "Facebook is seeking a Linux Kernel Software Engineer to join our Kernel team, with a primary focus on the networking subsystem. Our goal over the next few years is for the Linux kernel network stack to rival or exceed that of FreeBSD. The Facebook kernel team is responsible for developing fixes and new features that are primarily driven by internal needs and emerging industry trends. As a member of that team, you will play an integral role in improving kernel stability, performance, observability, and manageability. Additionally, you will help work with the wider Linux community including upstream developers, vendors, and optionally conferences. This position is full-time and located in our Menlo Park office."
The job candidate will also work on IPv6 improvements for the Linux kernel, investigate new protocols, etc.