CURLOPT_DNS_SHUFFLE_ADDRESSES

Section: curl_easy_setopt options (3)
Updated: November 04, 2020
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NAME

CURLOPT_DNS_SHUFFLE_ADDRESSES - Shuffle addresses when a hostname returns more than one

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DNS_SHUFFLE_ADDRESSES, long onoff);

DESCRIPTION

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

Addresses will not be reshuffled if a name resolution is completed using the DNS cache. CURLOPT_DNS_CACHE_TIMEOUT(3) 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 will be reordered randomly, their order will not be 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

All

EXAMPLE

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 7.60.0

RETURN VALUE

CURLE_OK or an error such as CURLE_UNKNOWN_OPTION.