如何在C/C++中构建自定义简单DNS服务器

#include<iostream>
#include <ldns/ldns.h>

int main(int argc, char *argv[]) {
    if (argc != 2) {
        std::cerr << "Usage: "<< argv[0] << " <zone_file>"<< std::endl;
        return 1;
    }

    ldns_zone *zone = ldns_zone_new_frm_file(argv[1]);
    if (!zone) {
        std::cerr << "Error loading zone file: "<< argv[1]<< std::endl;
        return 1;
    }

    ldns_resolver *resolver = ldns_resolver_new();
    ldns_resolver_set_dnssec(resolver, true);
    ldns_resolver_set_dnssec_cd(resolver, true);
    ldns_resolver_set_recursive(resolver, true);
    ldns_resolver_set_port(resolver, 53);
    ldns_resolver_set_usevc(resolver, false);

    ldns_rr_list *soa_records = ldns_zone_soa(zone);
    ldns_rr *soa_record = ldns_rr_list_rr(soa_records, 0);
    ldns_rdf *origin_rdf = ldns_rr_owner(soa_record);
    ldns_resolver_set_domain(resolver, origin_rdf);

    ldns_rr_list *ns_records = ldns_zone_rrs(zone);
    ldns_rr_list *ns_records_with_a = ldns_rr_list_with_rdf(ns_records, LDNS_RDF_TYPE_A);
    ldns_rr_list *ns_records_with_aaaa = ldns_rr_list_with_rdf(ns_records, LDNS_RDF_TYPE_AAAA);

    ldns_rr_list_cat(ns_records_with_a, ns_records_with_aaaa);
    ldns_resolver_set_nameservers(resolver, ns_records_with_a);

    ldns_pkt *pkt = ldns_pkt_query_new(zone, LDNS_RR_TYPE_SOA, LDNS_RR_CLASS_IN, LDNS_RD);
    ldns_pkt *response = ldns_resolver_send(resolver, pkt);

    if (ldns_pkt_tc(response)) {
        std::cerr << "Truncated response"<< std::endl;
        return 1;
    }

    if (ldns_pkt_get_rcode(response) != LDNS_RCODE_NOERROR) {
        std::cerr << "Error in response: " << ldns_pkt_rcode2str(ldns_pkt_get_rcode(response))<< std::endl;
        return 1;
    }

    ldns_rr_list *answer_section = ldns_pkt_answer(response);
    ldns_rr_list_print(stdout, answer_section);

    ldns_resolver_deep_free(resolver);
    ldns_pkt_free(pkt);
    ldns_pkt_free(response);
    ldns_zone_deep_free(zone);

    return 0;
}