Re: [PATCH bpf-next 0/3] bpf: add MPTCP subflow support

On Fri, Aug 21, 2020 at 05:15:38PM +0200, Nicolas Rybowski wrote:

Previously it was not possible to make a distinction between plain TCP
sockets and MPTCP subflow sockets on the BPF_PROG_TYPE_SOCK_OPS hook.

This patch series now enables a fine control of subflow sockets. In its
current state, it allows to put different sockopt on each subflow from a
same MPTCP connection (socket mark, TCP congestion algorithm, ...) using
BPF programs.

It should also be the basis of exposing MPTCP-specific fields through BPF.

Looks fine, but I'd like to see the full picture a bit better.
What's the point of just 'token' ? What can be done with it?
What are you thinking to add later?
Also selftest for new feature is mandatory.