[Planetlab-users] sendto: operation not permitted

[Danny Bickson]

you can use the "strace" Linux command by appending it to the command line
of your application.
Using it you will have a detailed debugging info of which system calls where
called by your application.
Using this log you can check where the EPERM error is generated from. (You
can send me a sample log if you like and I can look at it)

Best regards,


On 11/9/06, Patrick Verkaik <pverkaik at cs.ucsd.edu> wrote:
>
>
> Hi,
>
> I have a question about the following sendto() behaviour that I don't
> quite understand.
>
> We're sending raw TCP packets using sendto() but getting intermittent
> EPERM errors. We've found that repeatedly retrying the sendto() (with
> exactly the same packet) until it no longer gives EPERM eventually gets
> the packet through. During a short connection (perhaps lasting 10 seconds
> and sending across less than 100 bytes of data) we sometimes see about
> 100,000 failed sendto() attempts (with a usleep(1) separating the attempts
> roughly 20,000 attempts).
>
> Another curious fact is that we only see this behaviour when we're
> tunneling the reverse TCP traffic into the sending host. The host
> therefore doesn't see e.g. SYN/ACK packets coming back in response to
> outgoing SYNs.
>
> Can anyone explain this? Is this how Planetlab implements rate limiting or
> prevents SYN-flooding attacks being launched from Planetlab?
>
> (Btw: we're running as root and using the node's IP address as source IP
> address.)
>
>        Thanks,
>
>        Patrick Verkaik
>        Barath Raghavan
>
> _______________________________________________
> Users mailing list: Users at lists.planet-lab.org
> https://lists.planet-lab.org/mailman/listinfo/users
>



-- 
Danny Bickson,Ph.D. Student,
School of Computer Science and Engineering,
The Hebrew University of Jerusalem
Cell phone: +972-545-487421
US cell phone: (408) 550-3528
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