how to modify packet header(IP header, TCP Header) before the host send them into the network

Question

I want to modify packet header(IP header, TCP Header) before the host send them into the network.

For example, if I\'m using firefox for browsing, then I want to int

Answer 1

it should be for you Network packet capturing for Linux.

But it seems to intercept all process in the system.

---

maybe you can use

#include 
long ptrace (enum __ptrace_request request,
             pid_t pid,
             void *addr,
             void *data);

and hook send(2) or recv(2) to modify the tcp header.