option_total_len
write_opt.regular.len = option_total_len(test_opt->flags);
optlen = option_total_len(passive_synack_out.flags);
optlen = option_total_len(active_syn_out.flags);
optlen = option_total_len(opt->flags);
err = bpf_reserve_hdr_opt(skops, option_total_len(OPTION_MASK), 0);
write_opt.exprm.len = option_total_len(test_opt->flags);