---
name: "CURLOPT_DNS_INTERFACE"
section: "3"
platform: "linux"
package: "curl"
version: "8.23.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_DNS_INTERFACE"
---

# CURLOPT\_DNS\_INTERFACE(3)

interface to speak DNS over

## 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)](/curl_easy_setopt/3.md)* returns a CURLcode indicating success or error.

CURLE\_OK (0) means everything was OK, non-zero means an error occurred, see *[libcurl-errors(3)](/libcurl-errors/3.md)*.

## SEE ALSO

[**CURLOPT\_DNS\_LOCAL\_IP4**(3)](/CURLOPT_DNS_LOCAL_IP4/3.md), [**CURLOPT\_DNS\_LOCAL\_IP6**(3)](/CURLOPT_DNS_LOCAL_IP6/3.md), [**CURLOPT\_DNS\_SERVERS**(3)](/CURLOPT_DNS_SERVERS/3.md), [**CURLOPT\_INTERFACE**(3)](/CURLOPT_INTERFACE/3.md)