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CURLOPT_RESOLVER_START_FUNCcurl_easy_setopt CURLOPT_RESOLVER_START_FUNCTION(3)

NAME
       CURLOPT_RESOLVER_START_FUNCTION	-  set	callback to be called before a
       new resolve request is started

SYNOPSIS
       #include <curl/curl.h>

       int resolver_start_cb(void *resolver_state, void *reserved, void *userdata);

       CURLcode curl_easy_setopt(CURL *handle,
				 CURLOPT_RESOLVER_START_FUNCTION,
				 resolver_start_cb);

DESCRIPTION
       Pass a pointer to your callback function, which should match the proto-
       type shown above.

       This  callback  function gets called by libcurl every time before a new
       resolve request is started.

       resolver_state points to a backend-specific resolver  state.  Currently
       only  the ares resolver backend has a resolver state. It can be used to
       set up any desired option on the ares channel  before  it's  used,  for
       example setting up socket callback options.

       reserved is reserved.

       userdata     is	  the	 user	 pointer    set    with    the	  CUR-
       LOPT_RESOLVER_START_DATA(3) option.

       The callback must return 0 on success. Returning a non-zero value  will
       cause the resolve to fail.

DEFAULT
       NULL (No callback)

PROTOCOLS
       All

EXAMPLE
       static int resolver_start_cb(void *resolver_state, void *reserved,
				    void *userdata)
       {
	 (void)reserved;
	 printf("Received resolver_state=%p userdata=%p\n",
		resolver_state, userdata);
	 return 0;
       }

       CURL *curl = curl_easy_init();
       if(curl) {
	 curl_easy_setopt(curl, CURLOPT_RESOLVER_START_FUNCTION, resolver_start_cb);
	 curl_easy_setopt(curl, CURLOPT_RESOLVER_START_DATA, curl);
	 curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
	 curl_easy_perform(curl);
	 curl_easy_cleanup(curl);
       }

AVAILABILITY
       Added in 7.59.0

RETURN VALUE
       Returns CURLE_OK

SEE ALSO
       CURLOPT_RESOLVER_START_DATA(3)

libcurl 7.63.0		       February 14, CURLOPT_RESOLVER_START_FUNCTION(3)