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CURLOPT_RESOLVE(3)         curl_easy_setopt options         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 single name resolve string 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 "+" signifies whether the new entry should time-
       out or not. Entries added with "HOST:..." 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,
       then this entry will be removed and a new entry will be created. This
       is because the old entry may have have different addresses or a
       different time-out setting.

       The provided ADDRESS set by this option will be used even if
       CURLOPT_IPRESOLVE(3) is set to make libcurl use another IP version.

       Remove names from the DNS cache again, to stop providing these fake
       resolves, by including a string in the linked list that uses the format
       "-HOST:PORT". The host name must be prefixed with a dash, and the host
       name and port number must exactly match what was already added
       previously.

       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.


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.


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),

libcurl 7.76.0                 February 25, 2021            CURLOPT_RESOLVE(3)

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