Why would libhijack become more powerful with PTRACE_SEIZE?
As far as I can tell, it only makes ptracing more transparent,
not more powerful.
This example doesn't do anything that couldn't have been done
with normal ptrace, as far as I can tell.
And the whole approach is total madness. Why not just steal the
connection by passing the socket fd to the new target and closing
it in the original task? For that you only need to inject a couple
of system calls, with less disruptive data injections. No need to
muck around in TCP states, netfilter and all that other madness.