CURLOPT_DNS_INTERFACE(3) Introduction to Library Functions

NAME

CURLOPT_DNS_INTERFACE - interface to speak DNS over

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DNS_INTERFACE, char *ifname);

DESCRIPTION

Pass a char pointer as parameter. Set the name of the network
interface that the DNS resolver should bind to. This must be an
interface name (not an address). Set this option to NULL to use the
default setting (do not bind to a specific interface).

The application does not have to keep the string around after setting
this option.

Using this option multiple times makes the last set string override
the previous ones. Set it to NULL to disable its use again.

DEFAULT

NULL

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");
curl_easy_setopt(curl, CURLOPT_DNS_INTERFACE, "eth0");
result = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}

NOTES

This option requires that libcurl was built with a resolver backend
that supports this operation. The c-ares backend is the only such
one.

AVAILABILITY

Added in curl 7.33.0

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).

SEE ALSO

CURLOPT_DNS_LOCAL_IP4(3), CURLOPT_DNS_LOCAL_IP6(3),
CURLOPT_DNS_SERVERS(3), CURLOPT_INTERFACE(3)

libcurl 2026-01-08 CURLOPT_DNS_INTERFACE(3)