Linux platform debian 3.16.0-4-amd64.
Network traffic, when received from a network card, is copied immediately to user space, for a single program processing all network traffic. It is not known who handles the tcp / ip stack (kernel or not? Who knows, tell me). The source code of the handler program is missing (somehow it happened). There was a question how to log all network packets. Are there ways to intercept packets not from the kernel, but from user space?