Add a tcp option at the NAT device
 

Hello,

I am using a linux machine as NAT device which function is to map internal addresses 192.168.x.y to an external address.
What i want to do is to add a TCP option to SYN packets sent hosts.
I think that adding the TCP option has to be done in tcp_output.c file but I don't known in which function.

Anybody has an idea about such manipulation?

Thanks in advance.
hayf

It should be in tcp_transmit_skb function.