geticmpcodebynumber
ic = geticmpcodebynumber(r->type-1, r->code-1, r->af);
ic = geticmpcodebynumber(r->return_icmp >> 8,
ic6 = geticmpcodebynumber(r->return_icmp6 >> 8,
const struct icmpcodeent *geticmpcodebynumber(u_int8_t, u_int8_t, sa_family_t);