I have used Gentoo for about 3 years now. I'm enthusiast of this distribution because it gives me big choice of options. For a few months I am working on some Multipath TCP features. I have created an overlay with newest MPTCP kernel and net-tools supporting this protocol.
You can add it using layman:
sudo layman -o https://git.kolk.net.pl/gentoo/mptcp-overlay/plain/repositories.xml -f -a mptcp
You can read more about layman on Gentoo Wiki.
This overlay is in development. I have to add previous kernels and newest one. v4.15.2 is tested and working one.
sys-kernel/mptcp-sources is a mainline kernel including Multipath TCP
net-tools package containing extensions for Multipath TCP connections.