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CURLOPT_IPRESOLVE

Section: C Library Functions (3)
Updated: 202-0-19
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NAME

CURLOPT_IPRESOLVE - IP protocol version to use

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_IPRESOLVE, long resolve);

DESCRIPTION

Allows an application to select what kind of IP addresses to use when establishing a connection or choosing one from the connection pool. This is interesting when using hostnames that resolve to more than one IP family.

If the URL provided for a transfer contains a numerical IP version as a host name, this option does not override or prohibit libcurl from using that IP version.

Available values for this option are:

CURL_IPRESOLVE_WHATEVER: Default, can use addresses of all IP versions that your system allows.
CURL_IPRESOLVE_V4: Uses only IPv4 addresses.
CURL_IPRESOLVE_V6: Uses only IPv6 addresses.

DEFAULT

CURL_IPRESOLVE_WHATEVER

PROTOCOLS

This functionality affects all supported protocols

EXAMPLE

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/foo.bin");

    /* of all addresses example.com resolves to, only IPv6 ones are used */
    curl_easy_setopt(curl, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V6);

    result = curl_easy_perform(curl);

    curl_easy_cleanup(curl);
  }
}

HISTORY

CURL_IPRESOLVE_* macros became long types in 8.15.0, before this version a long cast was necessary when passed to curl_easy_setopt(3).

AVAILABILITY

Added in curl 7.10.8

RETURN VALUE

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).