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CURLOPT_INTERFACE(3)                libcurl               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.

       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 will 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

       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),

ibcurl 8.1.2                    April 26, 2023            CURLOPT_INTERFACE(3)

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