Hi Dear VPP，

I did some testing on the Stateful NAT64 feature last week and found that the tcp session never times out.

I checked the source code and found :
a. because nat64_tcp_session_set_state has not been called, nat64_db_st_entry_t.tcp_state == 0 (CLOSED)
b. calling nat64_session_reset_timeout, the nat64_db_st_entry_t.expire never be set