[$] Kernel operations structures in BPF
One of the more eyebrow-raising features to go into the 5.6 kernel is the
ability to load TCP congestion-control algorithms as BPF programs;
networking developer Toke Høiland-Jørgensen described it as a
continuation of the kernel's "march towards becoming BPF
runtime-powered microkernel". On its
face, congestion control is a significant new functionality to hand over to
BPF, taking it far
beyond its existing capabilities. When one looks closer, though, one's
eyebrow altitude may well increase further; the implementation of this
feature breaks new ground in a couple of areas.