Test if a socket accept is from external network

[jim.cromie at gmail.com]

On Sun, Apr 25, 2021 at 6:02 AM Jeffrey Walton <noloader at gmail.com> wrote:
>
> On Sun, Apr 25, 2021 at 7:09 AM John Wood <john.wood at gmx.com> wrote:
> >
> > I'm working in a LSM to detect and mitigate fork brute force attacks
> > against vulnerable userspace applications. Now, to fine tuning the
> > detection I want to detect a network activity.  ...
> > How can I detect that an external connection (using a net device) is
> > accepted and avoid internal network communication?
>
> One caveat that may (or may not) apply...
>
> Systemd opens sockets for services even when a service is disabled. It
> could appear that a system is accepting traffic even when the service
> is unavailable.
>
> Jeff
>

this is interesting, it lets systemd add a tarpit to stall those SYN
connections.
But maybe bpf will do this soon.