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 pointer 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 hostname. If you  prefer
       one of these, you can use the following special prefixes:

       *   if!<name>   -   Interface   name   *   host!<name>   -   IP   address  or  hostname  *
       ifhost!<interface>!<host> - Interface name and IP address or hostname

       If if! or ifhost! 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.

       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, use whatever the TCP stack finds suitable

PROTOCOLS

       This functionality affects all supported protocols

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);
         }
       }

HISTORY

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

       The ifhost! syntax was added in 8.9.0.

AVAILABILITY

       Added in curl 7.3

RETURN VALUE

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

SEE ALSO

       CURLOPT_LOCALPORT(3), CURLOPT_SOCKOPTFUNCTION(3), CURLOPT_TCP_NODELAY(3)