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CURLOPT_RESOLVE(3)                  libcurl                 CURLOPT_RESOLVE(3)


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:443:127.0.0.1");

       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),

ibcurl 8.1.2                    April 26, 2023              CURLOPT_RESOLVE(3)

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