Re: replacing tcp fields

From: Martin McSweeney (mmcsween@hopper.math.uwaterloo.ca)
Date: Fri Apr 27 2001 - 12:02:42 EST


On Fri, 27 Apr 2001, Karl Williams wrote:

> Thanks for the idea. However, looking over the netfilter information,
> it seems that I can only specify certain TCP fields to mangle.
> I don't see where I can manipulate the checksum and/or data fields.
> Am I missing something?
>

No, once you have a packet in userspace you have access to all the fields
in tcp.h.. including checksum.

> >You can obviously use Netfilter (netfilter.kernelnotes.org) with queueing
> >rules in the OUTPUT chain.
> >
> >On Thu, 26 Apr 2001, Karl Williams wrote:
> >
> >> >> I need to replace the data field and the checksum field in a tcp packet with other information (not related to the socket or socket buffer).
> >>
> >> >Where is the packet originating from? Does it originate from a program on
> >> >your computer, or some other machine addressed to your computer, or just
> >> >forwarded through your computer?
> >>
> >> The packet itself is generated on my own machine. I assume it's using the TCP subroutines in the .../net/ipv4 directory.
>
>
>
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