ip_fw3_nat_state_cmp
RB_PROTOTYPE(state_tree, nat_state, entries, ip_fw3_nat_state_cmp);
RB_GENERATE(state_tree, nat_state, entries, ip_fw3_nat_state_cmp);
int ip_fw3_nat_state_cmp(struct nat_state *s1, struct nat_state *s2);