From mboxrd@z Thu Jan  1 00:00:00 1970
From: A K A <gello666@yahoo.com>
Subject: NF_STOLEN effect on TCP
Date: Tue, 11 Nov 2003 11:13:18 -0800 (PST)
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(include my address in the replies, i am not
subscribed to the list).


hello all,



Ok I have been stuck on this for tooo long and cant
figure it out. I have made an LKM which registers to
NF_POST_ROUTING hook. it gets a packet and if matches
a certain criterion then it puts it on to my private
Queue and returns NF_STOLEN. By putting the packet on
the Queue I am delaying the packets by arround 4 ms.

Now here is the problem for the case of a TCP packet:
A TCP SYN was selected to be delayed. So my hook
returns NF_STOLEN and the packet is sent 4 ms latter
using ip_send(), initated by an ioctl called from a
user application. next my host receives a syn+ack
and imediately sends an ack. However the first data
packet is sent out at a delay arround 4ms also. which
is very odd. cuz in the user application the send
function is called right after connect. I was
expecting only the syn packet to be affected because
of my delay, but there is some sort of reaction.

I dont think that its because of some RTT calculations
because when i send the SYN packet imdediately and
delay it at the peer then the first data packet goes
on fine.

Now I have been stuck with this damn thing for a long
while and cant figure out---is it the stealing that
results in this. is this some expected behavior of
TCP. .. please can u help me with this soon.


regards,

Asad

ps: i can send you a trace plot of the tcp seq vs time
as an attachment if you would like to see it.

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