c++ - Linux c++ : getaddrinfo failed with EAI_AGAIN, curl 无法解析主机

Question

我通过 ppp 打开 GSM 连接并尝试使用 curl 从 URL 下载文件。

对于少数设备，curl 和 getaddrinfo 导致 EAI_AGAIN 出现 CURLE_COULDNT_RESOLVE_HOST 错误。

在 route 中，我的 ppp0 接口(interface)注册正确。 resolv.conf 包含 google DNS 并且在终端中手动执行 nslookup 是有效的。

我不知道为什么它不起作用。我唯一知道的是:IPv6 是不可能的。

这是我的getaddrinfo

代码

int checkINet(std::string address)
{
   struct addrinfo hints, *servinfo, *p;
   memset(&hints, 0, sizeof(hints));
   hints.ai_family = AF_INET;
   hints.ai_socktype = SOCK_STREAM;
   char ip_addr[INET6_ADDRSTRLEN];

   int s = getaddrinfo(address.c_str(), NULL, &hints, &servinfo);

   if (s != 0)
   {
      std::cout << "No connection possible: " << address << "\n";
      std::cout << "getaddrinfo: " << s << " " << gai_strerror(s) << "\n";
      return -1;
   }
   else
   {
      std::cout << "Conection successful: " << address << "\n";

      for (p = servinfo; p != NULL; p = p->ai_next)
      {
         void *addr;
         if (p->ai_family == AF_INET)
         {
            struct sockaddr_in *ipv4 =(struct sockaddr_in *)p->ai_addr;
            addr = &(ipv4->sin_addr);
         }
         else
         {
            struct sockaddr_in6 *ipv6 =(struct sockaddr_in6 *)p->ai_addr;
            addr = &(ipv6->sin6_addr);
         }

         inet_ntop(p->ai_family, addr, ip_addr, sizeof ip_addr);
         std::cout << addr << "\n";
      }

   }
   freeaddrinfo(servinfo);
   return 0;
}

对于 curl :

   CURL *curl;
   FILE *fp;
   CURLcode res;

   // initialise a connection to the server
   curl = curl_easy_init();
   if (curl)
   {
      fp = fopen(UPDATE_ZIP, "wb");
      curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
      curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);
      curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
      curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
      curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
      curl_easy_setopt(curl, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4);
      res = curl_easy_perform(curl);
      curl_easy_cleanup(curl);
      fclose(fp);

      if (CURLE_OK != res)
      {
          std::out << "curl failed with: " << res << "\n";
          return res;
      }
      return 0;
   }
   return -1;

Answer 1

ephemient tipp 是对的。更改了 /etc/nsswitch.con 中的顺序主机:文件 dns到主机:dns 文件