Provided by: libcurl4-doc_7.81.0-1ubuntu1.20_all bug

NAME

       CURLOPT_RESOLVE - provide custom host name to IP address resolves

SYNOPSIS

       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_RESOLVE,
                                 struct curl_slist *hosts);

DESCRIPTION

       Pass  a  pointer  to a linked list of strings with host name resolve information to use for requests with
       this handle. The linked list should be a fully valid list of struct curl_slist  structs  properly  filled
       in. Use curl_slist_append(3) to create the list and curl_slist_free_all(3) to clean up an entire list.

       Each resolve rule to add should be written using the format

        [+]HOST:PORT:ADDRESS[,ADDRESS]

       ...  where  HOST  is  the  name libcurl will try to resolve, PORT is the port number of the service where
       libcurl wants to connect to the HOST and ADDRESS is one or more numerical IP addresses.  If  you  specify
       multiple  ip  addresses  they need to be separated by comma. If libcurl is built to support IPv6, each of
       the ADDRESS entries can of course be either IPv4 or IPv6 style addressing.

       This option effectively pre-populates the DNS cache with entries for the host+port pair so redirects  and
       everything that operations against the HOST+PORT will instead use your provided ADDRESS.

       The  optional leading "+" specifies that the new entry should time-out. Entries added without the leading
       plus character will never time-out whereas  entries  added  with  "+HOST:..."  will  time-out  just  like
       ordinary DNS cache entries.

       If  the  DNS  cache  already  has  an entry for the given host+port pair, the new entry will override the
       former one.

       An  ADDRESS  provided  by  this  option  will  only  be  used  if  not  restricted  by  the  setting   of
       CURLOPT_IPRESOLVE(3) to a different IP version.

       To  remove names from the DNS cache again, to stop providing these fake resolves, include a string in the
       linked list that uses the format

         -HOST:PORT

       The entry to remove must be prefixed with a dash, and the host name and port number  must  exactly  match
       what was added previously.

DEFAULT

       NULL

PROTOCOLS

       All

EXAMPLE

       CURL *curl;
       struct curl_slist *host = NULL;
       host = curl_slist_append(NULL, "example.com:80:127.0.0.1");

       curl = curl_easy_init();
       if(curl) {
         curl_easy_setopt(curl, CURLOPT_RESOLVE, host);
         curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

         curl_easy_perform(curl);

         /* always cleanup */
         curl_easy_cleanup(curl);
       }

       curl_slist_free_all(host);

AVAILABILITY

       Added in 7.21.3. Removal support added in 7.42.0.

       Support for providing the ADDRESS within [brackets] was added in 7.57.0.

       Support for providing multiple IP addresses per entry was added in 7.59.0.

       Support for adding non-permanent entries by using the "+" prefix was added in 7.75.0.

RETURN VALUE

       Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.

SEE ALSO

       CURLOPT_IPRESOLVE(3), CURLOPT_DNS_CACHE_TIMEOUT(3), CURLOPT_CONNECT_TO(3),