c++ - libcurl如何判断域名解析失败

Question

默认使用libcurl请求域名的时候，如果域名解析失败会返回一个CURLE_COULDNT_RESOLVE_HOST (6)的错误

但是，如果当你的DNS被运营商劫持后，运营商会返回给你一个错误页面（联通的是wo.com.cn，电信的是114dns）,所以这个时候curl获取的结果实际上是这个错误页面，而误认为是请求成功

为了解决这一问题，我尝试获取最终返回的URL地址 与请求的URL地址来进行对比，然后判断
，例如下面的代码

curl = curl_easy_init();
curl_easy_setopt(curl, CURLOPT_URL, urlStr);
curl_easy_setopt(curl, CURLOPT_TIMEOUT, 5);
curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION,1);
res = curl_easy_perform(curl);               
curl_easy_getinfo(curl,CURLINFO_EFFECTIVE_URL,&response_url);

然而事与愿违，最终得到的reponse_url仍然是我请求的url地址而非最终返回的URL地址，所以再次询问各位有没有好的解决方案？

Answer 1

You can first use nslookup to resolve a non-existent domain name, such as nslookup xxxxxxxx. If China Telecom does DNS hijacking, you will resolve an IP address. For example, Shanghai Telecom's fake IP is 180.168.41.175.

Install a dnsmasq as your DNS server, write in the dnsmasq configuration file:

server=223.5.5.5 # AliDNS server
bogus-nxdomain=180.168.41.175

Then configure 127.0.0.1 as your DNS server address.

After being configured in this way, dnsmasq will return a domain not exist response to the downstream when the upstream DNS returns 180.168.41.175, so that you can get accurate error information.