Kernel starts dropping incoming ping packets

I am writing a device driver for a modem.  I can successfully
continuously ping to my modem  for 8 to 10 minutes.  After that, I can
no longer ping to it, but I can ping from it.  I have determined that
at that point I am still  receiving the ping packets and sending them
to the kernel, just as I had when the pings were successful, but I am
no longer receiving ping packets from the kernel to transmit back.

Once it gets into this state, I have noticed that the "arp" and
"route" commands take an extra long time to complete.  Other commands
are not slowed down.  The "top" command does not show any
extraordinary memory usage by any process.  I am running Linux 2.6.10
on a PowerPC processor.  Any suggestions as to what may be going on?

Bill wrote:
> I am writing a device driver for a modem.  I can successfully
> continuously ping to my modem  for 8 to 10 minutes.  After that, I can
> no longer ping to it, but I can ping from it.  I have determined that
> at that point I am still  receiving the ping packets and sending them
> to the kernel, just as I had when the pings were successful, but I am
> no longer receiving ping packets from the kernel to transmit back.
> 
> Once it gets into this state, I have noticed that the "arp" and
> "route" commands take an extra long time to complete.  Other commands
> are not slowed down.  The "top" command does not show any
> extraordinary memory usage by any process.  I am running Linux 2.6.10
> on a PowerPC processor.  Any suggestions as to what may be going on?

The kernel thinks you're a DOS attack?

On May 28, 7:26=A0pm, Jim Stewart <jstew...@jkmicro.com> wrote:
> Bill wrote:
> > I am writing a device driver for a modem. =A0I can successfully
> > continuously ping to my modem =A0for 8 to 10 minutes. =A0After that, I c=
an
> > no longer ping to it, but I can ping from it. =A0I have determined that
> > at that point I am still =A0receiving the ping packets and sending them
> > to the kernel, just as I had when the pings were successful, but I am
> > no longer receiving ping packets from the kernel to transmit back.
>
> > Once it gets into this state, I have noticed that the "arp" and
> > "route" commands take an extra long time to complete. =A0Other commands
> > are not slowed down. =A0The "top" command does not show any
> > extraordinary memory usage by any process. =A0I am running Linux 2.6.10
> > on a PowerPC processor. =A0Any suggestions as to what may be going on?
>
> The kernel thinks you're a DOS attack?

There might be an configuration which if enabled could respond to a
DOS attack. However most of the public servers are pinged contineously
by many network operators and i havent seen a situation where in the
ping response is not sent back as described. I would try to see if the
IP is lost during this process.

How is the network set up? How did u determine you have received a
ping packet? I would also use network analyzer to detect the messages
on the network. There are free analyzing software online which you
could use.

PROBLEM SOLVED.  I was not freeing the TX socket buffers after
transferring the data out of them.