NAME

       CURLOPT_RESOLVER_START_FUNCTION - callback called before a new name resolve 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 prototype 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 CURLOPT_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, "https://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)