Re: How To Temporarily Suspend Network Traffic
On Tue, Feb 01, 2011 at 08:26:53PM +0200, Volkan YAZICI wrote:
> On Tue, 1 Feb 2011 13:15:15 -0500, Gregory Seidman writes:
> > On Tue, Feb 01, 2011 at 07:40:06PM +0200, Volkan YAZICI wrote:
> >> [...]
> >> # while /bin/true; do \
> >> > iptables -A OUTPUT -i wlan0 -j DROP && \
> >> > usleep 100000 && \
> >> > iptables -D OUTPUT -i wlan0 -j DROP
> >>
> >> command (usleep is a small C program I wrote, see the attachment),
> >> transfer hangs after some point and stops for ~30-40secs and finishes
> >> when I stop the while loop. Do I miss anything? Any suggestions?
> >
> > Here you are interrupting for 100,000 usecs (which is 100msecs, I believe),
> > but you don't sleep at all between interruptions in the while loop. That
> > means that it only has the time between the execution of the iptables
> > command at the end of the loop and the execution of the iptables command at
> > the beginning of the loop to actually transmit any packets. It is
> > unsurprising that it hangs. Make sure you sleep for a while after removing
> > the iptables rule.
>
> Indeed, sleeping more than I want is what I try to avoid. In other
> words, I'm inclined to believe that running iptables externally doesn't
> provide an interruption mechanism in milli/microsecond granularity. Any
> other suggestions?
Well, I suggested before that you look into the iptables code and make the
system calls it does rather than executing it externally.
> Regards.
--Greg
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