CURLOPT_INTERFACE(3)       curl_easy_setopt options       CURLOPT_INTERFACE(3)

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 as only as
       interface name and no attempt will ever be named to do treat it as an
       IP address or to do name resolution on it.  If the parameter starts
       with "host!" it is treated as either an IP address or a hostname.
       Hostnames are resolved synchronously.  Using the if! format is highly
       recommended when using the multi interfaces to avoid allowing the code
       to block.  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.

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

         curl_easy_setopt(curl, CURLOPT_INTERFACE, "eth0");

         ret = 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),

libcurl 7.77.0                 November 4, 2020           CURLOPT_INTERFACE(3)