Sock is initialized in funtion tcp_v4_init_sock() (net/ipv4/tcp_ipv4.c). T/TCP related initialization is as follows:
tp->do_rfc1644 = 1;
tp->cc_cache.cc_recv = 0;
tp->cc_cache.cc_send = ttcp_gen;
In default, all T/TCP functions are turned on with tp->do_rfc1644=1 (see above). However, you can turn it off by calling setsockopt() with option name "TTCP" and option value "0".