Re: How To Temporarily Suspend Network Traffic
On 2011-02-15, Kelly Dean kellydea...@yahoo.com wrote: lrhorer wrote: Volkan YAZICI wrote: I want to temporarily suspend the network traffic on a particular interface -- if possible, in microsecond granularity. I have to ask. Why are you wanting to do this? It seems a truly bizarre request. Maybe in order to simulate intermittent RFI on wireless networks, in order to see how TCP responds. (Hint: it responds very stupidly.) Another example is the testing of message queues. Any messaging system worthy of the name will need to react gracefully in such situations. -- Liam O'Toole Cork, Ireland -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/slrniln4b8.2hf.liam.p.otoole@dipsy.tubbynet
Re: How To Temporarily Suspend Network Traffic
lrhorer wrote: Volkan YAZICI wrote: I want to temporarily suspend the network traffic on a particular interface -- if possible, in microsecond granularity. I have to ask. Why are you wanting to do this? It seems a truly bizarre request. Maybe in order to simulate intermittent RFI on wireless networks, in order to see how TCP responds. (Hint: it responds very stupidly.) -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/17203.71263...@web121506.mail.ne1.yahoo.com
Re: How To Temporarily Suspend Network Traffic
On Tue, Feb 01, 2011 at 03:44:57PM +, T o n g wrote: On Tue, 01 Feb 2011 09:16:16 -0500, Gregory Seidman wrote: Now, those are the actual commands to run from the shell. You aren't going to get microsecond granularity that way. FYI, $ apt-cache show sleepenh Package: sleepenh Priority: extra Section: universe/utils Installed-Size: 60 Maintainer: Ubuntu MOTU Developers ubuntu-m...@lists.ubuntu.com ^^ Huh? Original-Maintainer: Pedro Zorzenon Neto p...@debian.org Architecture: amd64 Version: 1.3-1 Depends: libc6 (= 2.3.4) Whereas: $ apt-cache show sleepenh Package: sleepenh Priority: extra Section: utils Installed-Size: 60 Maintainer: Pedro Zorzenon Neto p...@debian.org Architecture: amd64 Version: 1.3-1 Depends: libc6 (= 2.7-1) Notice the different dependency versions? -- Religion is excellent stuff for keeping common people quiet. -- Napoleon Bonaparte -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20110204070736.GE18972@fischer
How To Temporarily Suspend Network Traffic
Hi, I want to temporarily suspend the network traffic on a particular interface -- if possible, in microsecond granularity. For this purpose, ifup/ifdown ioctl() calls doesn't work. That is, for wireless, connection isn't get recovered; for wired, it takes at least 2 seconds to recover. I tried using tc, but it doesn't accept rate 0 parameter. Neither iwconfig wlan0 rate 0 has any effect. (Moreover, in iwconfig manual it is told that values below 1000 are card specific and are usually an index in the bit-rate list.) Do you have any suggestions? Or can you point me to some other resource/mailing-list that I can consult? Regards. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/87tygnamfe@alamut.ozu.edu.tr
Re: How To Temporarily Suspend Network Traffic
On Tue, Feb 01, 2011 at 03:56:05PM +0200, Volkan YAZICI wrote: I want to temporarily suspend the network traffic on a particular interface -- if possible, in microsecond granularity. For this purpose, ifup/ifdown ioctl() calls doesn't work. That is, for wireless, connection isn't get recovered; for wired, it takes at least 2 seconds to recover. I tried using tc, but it doesn't accept rate 0 parameter. Neither iwconfig wlan0 rate 0 has any effect. (Moreover, in iwconfig manual it is told that values below 1000 are card specific and are usually an index in the bit-rate list.) Do you have any suggestions? Or can you point me to some other resource/mailing-list that I can consult? It depends on exactly what behavior you're aiming for. If you just want all packets going in or out on that interface to be dropped, you can do it pretty effectively with iptables. The following will drop all packets coming in through the wlan0 interface: iptables -A PREROUTING -i wlan0 -j DROP This will drop all packets destined to be sent out the wlan0 interface: iptables -A POSTROUTING -o wlan0 -j DROP You can remove each rule by changing the -A to a -D. Now, those are the actual commands to run from the shell. You aren't going to get microsecond granularity that way. You can, however, dig into the iptables source and see what system calls it's making as a result of those options and use it in your own code. I don't know if that will get you to microsecond granularity, but you'll have to do your own profiling to check. Regards. --Greg -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20110201141616.gf11...@anthropohedron.net
Re: How To Temporarily Suspend Network Traffic
On Tue, Feb 01, 2011 at 07:40:06PM +0200, Volkan YAZICI wrote:
On Tue, 1 Feb 2011 09:16:16 -0500, Gregory Seidman writes:
[...]
Thanks Greg, but there is a small anomaly with this method. For
instance, if I
1. issue
$ pv -q -L 10k /tmp/200k.dat | nc 192.168.1.1 7000
from terminal A,
2. and after a few seconds issue
# iptables -A OUTPUT -i wlan0 -j DROP \
sleep 2 \
iptables -D OUTPUT -i wlan0 -j DROP
command (pay attention that I used OUTPUT chain instead of
{PRE,POST}ROUTING), as expected, transfer hangs up for 2 seconds, and
finishes without a problem.
I note that you are only doing this once, so there is a 2 second
interruption as expected.
On the other hand, in the 2nd step, if I issue
# while /bin/true; do \
iptables -A OUTPUT -i wlan0 -j DROP \
usleep 10 \
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.
Best.
--Greg
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Re: How To Temporarily Suspend Network Traffic
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 10 \ 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? Regards. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/87oc6v391u@alamut.ozu.edu.tr
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 10 \ 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 -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/20110201183526.gi11...@anthropohedron.net
Re: How To Temporarily Suspend Network Traffic
Volkan YAZICI wrote: Hi, I want to temporarily suspend the network traffic on a particular interface -- if possible, in microsecond granularity. For this purpose, ifup/ifdown ioctl() calls doesn't work. That is, for wireless, connection isn't get recovered; for wired, it takes at least 2 seconds to recover. I tried using tc, but it doesn't accept rate 0 parameter. Neither iwconfig wlan0 rate 0 has any effect. (Moreover, in iwconfig manual it is told that values below 1000 are card specific and are usually an index in the bit-rate list.) Do you have any suggestions? Or can you point me to some other resource/mailing-list that I can consult? I have to ask. Why are you wanting to do this? It seems a truly bizarre request. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of unsubscribe. Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/uoidnytcaogzg9xqnz2dnuvz5qedn...@giganews.com
