Userspace TCP sequence number control?

Hello,

If there's a forum more specifically dedicated to 2.4 networking, please point me in the right direction, otherwise please consider the following. (I'm on lkml so you don't need to CC: me)

Is there a way to set the sequence number sent in the SYN response to an incoming connnection request (an incoming SYN) to a specific value with listen()?

It may sound like a security risk, but consider the problem of trying to do http load balancing using 2.4 netfilter, (ie in kernel, packet/conntrack-based) but trying to maintain session affinity
to a specific backend server.

Clearly, the load balancer must open a http (and thus TCP) connection to determine the client that is connecting, in order to determine which back-end server is already servicing
the user session. Typically, from this point on, the load balancer
must just copy the data back and forth between the socket connected to the client and another socket. This could be userspace or kernelspace, but it's copying either way.

What if the connection could be handed off via DNAT *after* it had been established? The load balancer could establish a connection with the backend server, posing as the client, setup an iptable entry directing the client connection's packets to the backend server, then close it's connection (somehow without sending FIN)...

the (big) part missing is that the backend server's sequence number will differ from the one used by the load-balancer. (whereas the load balancer can just copy the last sequence number recieved by the client)

Does this functionality exist already? Or can
iptables re-write the sequence numbers ?
(Cisco's PIX does this to re-randomize them
for hosts inside firewall that have poor random
number generation)

Am I talking crazy talk already?
(I know I should research the tunneling
method more)

Regards,

Jeremy