curl / libcurl / API / curl_easy_setopt / CURLOPT_DNS_SHUFFLE_ADDRESSES

CURLOPT_DNS_SHUFFLE_ADDRESSES explained

Name

CURLOPT_DNS_SHUFFLE_ADDRESSES - shuffle IP addresses for hostname

Synopsis

#include <curl/curl.h>
 
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DNS_SHUFFLE_ADDRESSES, long onoff);

Description

Pass a long set to 1 to enable this option.

When a name is resolved and more than one IP address is returned, this function shuffles the order of all returned addresses so that they are used in a random order. This is similar to the ordering behavior of the legacy gethostbyname function which is no longer used on most platforms.

Addresses are not reshuffled if name resolution is completed using the DNS cache. CURLOPT_DNS_CACHE_TIMEOUT can be used together with this option to reduce DNS cache timeout or disable caching entirely if frequent reshuffling is needed.

Since the addresses returned are randomly reordered, the order is not in accordance with RFC 3484 or any other deterministic order that may be generated by the system's name resolution implementation. This may have performance impacts and may cause IPv4 to be used before IPv6 or vice versa.

Default

0 (disabled)

Protocols

This functionality affects all supported protocols

Example

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
    curl_easy_setopt(curl, CURLOPT_DNS_SHUFFLE_ADDRESSES, 1L);
 
    curl_easy_perform(curl);
 
    /* always cleanup */
    curl_easy_cleanup(curl);
  }
}

Availability

Added in curl 7.60.0

Return value

CURLE_OK or an error such as CURLE_UNKNOWN_OPTION.