modification of tcp flags using netfilter hooks??

Hello,
I have wriiten a module using netfilter hooks for catching
packets n then modifying it.. First using NF_IP_PRE_ROUTING hook i am
trying to modify the incoming tcp packet.. I want to change the tcp
flags for the incoming packet..I have handled the checksum issues for
that.. What othere issues i need to handle???
Thanks...

Regards
Sunny

"Sunny" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) oups.com
> Hello,
> I have wriiten a module using netfilter hooks for catching
> packets n then modifying it.. First using NF_IP_PRE_ROUTING hook i am
> trying to modify the incoming tcp packet.. I want to change the tcp
> flags for the incoming packet..I have handled the checksum issues for
> that.. What othere issues i need to handle???

It depends on which flags you're working.
If it's on URG, you've got to see the urgent pointer in the header.

If you touch SYN, FIN, ACK or RST, you should'nt count on a normal
TCP/IP
connection.


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