Would like know when the tcp sequence no is rollover

Would like know when the tcp sequence no is rollover

[Ramana Reddy]

Hi all,

I would like to know, when the TCP sequence no is rollover.
Who will do it. Is it happens in tcp code or through the hardware.
If is it is in the tcp code, can some one please point the code in the
linux kernel
where it happens.

Thanks & Regards,
Ramana
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Would like know when the tcp sequence no is rollover

[Bjørn Mork]

Ramana Reddy <gtvrreddy@gmail.com> writes:

> Hi all,
>
> I would like to know, when the TCP sequence no is rollover.
> Who will do it. Is it happens in tcp code or through the hardware.
> If is it is in the tcp code, can some one please point the code in the
> linux kernel
> where it happens.

Why this interest in TCP sequence numbers?

I believe RFC793 is a better source for understanding how this works:

  It is essential to remember that the actual sequence number space is
  finite, though very large.  This space ranges from 0 to 2**32 - 1.
  Since the space is finite, all arithmetic dealing with sequence
  numbers must be performed modulo 2**32.

Do you still think you'll find an explicit rollover code path? Why would
you write code like that?


Bj?rn

Would like know when the tcp sequence no is rollover

[Ramana Reddy]

Hi Bj?rn,

Thanks for your reply. Actually, I want to do some small experiment, so
would need this tcp sequence roll over code.
If you know some thing in this regards, please let me know.

Thanks & Regards,
Ramana

On Fri, Sep 18, 2015 at 7:17 PM, Ramana Reddy <gtvrreddy@gmail.com> wrote:

> Hi,
> Thanks for your reply. Actually, I want to restrict the TCP Sequence range
> to a half range and rollover after
> crosses that value. In anotherway, I want to use only half the TCP
> sequence and once it crosses that value will rollover.
>
> Thanks,
> Ramana
>
>
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Would like know when the tcp sequence no is rollover

[Bjørn Mork]

Ramana Reddy <gtvrreddy@gmail.com> writes:

> Hi Bj?rn,
>
> Thanks for your reply. Actually, I want to do some small experiment, so
> would need this tcp sequence roll over code.
> If you know some thing in this regards, please let me know.

There isn't much more to say, I think.  All that's left is hard work.
Since there is no existing rollover logic, you'll have to track down
every single sequence number calculation in the kernel and modify them
with additional rollover code.  Note that this includes every sequence
number comparison too.

I'm afraid I still don't see the point.  The end result will of course
not be TCP anymore, and will only be capable of talking to itself.  What
use is that?


Bj?rn