dns_service_c/src/set_resolvs.c

#include "settings.h"

#define DNSMASQ_RESOLV_FILE_TMP "resolv.conf.tmp"

char *set_resolvs(cJSON *resolvs) {
  FILE *resolvs_file_tmp = fopen(DNSMASQ_RESOLV_FILE_TMP, "w");
  if (!resolvs_file_tmp) {
    return "Failed to open resolv file";
  }

  cJSON *resolv = resolvs->child;
  while (resolv) {
    if (!cJSON_IsString(resolv)) {
      remove(DNSMASQ_RESOLV_FILE_TMP);
      return "Invalid resolv";
    }
    fprintf(resolvs_file_tmp, "nameserver %s\n", resolv->valuestring);
    resolv = resolv->next;
  }

  fclose(resolvs_file_tmp);

  if (rename(DNSMASQ_RESOLV_FILE_TMP, "/etc/dnsmasq.conf.d/resolv.conf") != 0) {
    remove(DNSMASQ_RESOLV_FILE_TMP);
    return "Failed to rename resolv file";
  }
  remove(DNSMASQ_RESOLV_FILE_TMP);
  return nullptr;
}