NAME

       CURLOPT_INTERFACE - source interface for outgoing traffic

SYNOPSIS

       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_INTERFACE, char *interface);

DESCRIPTION

       Pass  a  char  *  as  parameter.  This  sets the interface name to use as outgoing network
       interface. The name can be an interface name, an IP address, or a host name.

       If the parameter starts with "if!" then it is treated only as an interface  name.  If  the
       parameter starts with "host!" it is treated as either an IP address or a hostname.

       If   "if!"  is  specified  but  the  parameter  does  not  match  an  existing  interface,
       CURLE_INTERFACE_FAILED is returned from the libcurl function used to perform the transfer.

       libcurl does not support using network interface names for this option on Windows.

       We strongly advise against specifying the interface with a hostname, as it causes  libcurl
       to do a blocking name resolve call to retrieve the IP address. That name resolve operation
       does not use DNS-over-HTTPS even if CURLOPT_DOH_URL(3) is set.

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

DEFAULT

       NULL, use whatever the TCP stack finds suitable

PROTOCOLS

       All

EXAMPLE

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

           curl_easy_setopt(curl, CURLOPT_INTERFACE, "eth0");

           res = curl_easy_perform(curl);

           curl_easy_cleanup(curl);
         }
       }

AVAILABILITY

       The "if!" and "host!" syntax was added in 7.24.0.

RETURN VALUE

       Returns CURLE_OK on success or CURLE_OUT_OF_MEMORY if there was insufficient heap space.

SEE ALSO

       CURLOPT_SOCKOPTFUNCTION(3), CURLOPT_TCP_NODELAY(3)