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Re: pingflood.c
From: pedward () WEBCOM COM (pedward () WEBCOM COM)
Date: Mon, 18 May 1998 12:37:24 -0700



On most machines select returns -1, errno=EINTR on a signal that is handled.


You are correct. To fix the original code I posted, here goes:


[note, it will probably take longer than the interval, because of the number of
calls involved, but that's your thing]

void mysleep(int seconds)
{
        struct timeval tv_now;
        struct timeval tv_then;
        struct timeval tv;

        tv.tv_sec=seconds;
        tv.tv_usec=0;

        gettimeofday(&tv_now);

        tv_then.tv_sec = tv_now.tv_sec + seconds;
        tv_then.tv_usec = 0;

        while(select(0,NULL,NULL,NULL,&tv) != 0) {
                gettimeofday(&tv_now);

                tv.tv_sec = tv_then.tv_sec - tv_now.tv_sec;
                tv.tv_usec = tv_then.tv_usec - tv_now.tv_usec;

        }

}

There you go.  It just shows how such an insignificant little thing can consume a lot
of time to solve.


Also the real problem is much more fundamental than all of the ping -f
arguments. Consider

      fork 10 pings
      while(1)
      {
              kill all pings
              as we get sigcld fork new ones
              delay (not long)
      }

Another ping -f style attack. Or I could use UDP to send billions of
packets - far far simpler.


I concur, UDP is fully user level, and it can be programmed much easier than ICMP.


There is only one serious way to handle this, and it goes beyond the
conventional Unix networking. Like any other resource you quota users
in packets/bytes per second. Secure network folk would probably like a per
user BPF filter that must say Yes to any packet the user attempts to send
as well. I don't think anyone is addressing this right now.

Alan


--Perry

--
Perry Harrington        System Software Engineer    zelur xuniL  ()
http://www.webcom.com  perry.harrington () webcom com  Think Blue.  /\



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