[OLPC Security] P_NETWORK and system responsiveness

[Michael Stone]

On Sat, Dec 01, 2007 at 06:45:12PM -0500, Albert Cahalan wrote:
> On Dec 1, 2007 5:33 PM, Michael Stone <michael at laptop.org> wrote:
> 
> > Since you seem to have deeper familiarity with the iptables stuff than I
> > do, would you be willing to contribute a patch on top of Marcus'
> > permissions work [1] that implements a basic on/off switch for IP-based
> > network access?
> 
> I'm happy to help, although my time is spread thin and
> that's a pile of python code. I could write a shell script
> for you. If you wish, you could translate from bash to python.
> Would that be much help?

That would be great. 

> I'm thinking that the script might take a UID number as the
> first argument. Maybe there would be two scripts, for turning
> on and turing off. It may be better to have the script take a
> list of UIDs to block, or a list of UIDs to allow, with all the
> old state getting replaced.

I'm amenable to completely resetting the firewall state each time we
want to change it. 

> I was suggesting just the opposite though. Step back
> and take a look at the situation we have. If a process
> misbehaves severely, the user will hit the power button.
> They will then NOT run that program again. This is OK.
> It's very simple. There are no limits or UI issues to
> bother with.
> 
> It is strongly desireable to let activities hog the CPU.
> This allows activities to do reliable low-latency audio,
> reliable experiment control, reliable radio modems, etc.
> Thus the restriction of SCHED_FIFO and SCHED_RR
> to root should be relaxed, as is done for many of the
> Linux distributions that are meant for musicians.

Ah, okay. Hmm. I don't currently know enough about the scheduler
subsystem to really evaluate the merit of your suggestion, but I will
certainly consider it as the need arises.

Anyway, thanks for your suggestions and for your assistance with the
first piece of the network isolation feature.

Michael