External/Libraries/CURL/share/man/man3/CURLOPT_RESOLVE.3

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.TH CURLOPT_RESOLVE 3 "January 02, 2023" "libcurl 7.88.1" "curl_easy_setopt options"

.SH NAME
CURLOPT_RESOLVE \- provide custom host name to IP address resolves
.SH SYNOPSIS
.nf
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_RESOLVE,
                          struct curl_slist *hosts);
.SH 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 \fBstruct curl_slist\fP structs properly filled in. Use
\fIcurl_slist_append(3)\fP to create the list and \fIcurl_slist_free_all(3)\fP
to clean up an entire list.

Each resolve rule to add should be written using the format

.nf
 [+]HOST:PORT:ADDRESS[,ADDRESS]
.fi

\&... 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 \fICURLOPT_IPRESOLVE(3)\fP 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

.nf
  -HOST:PORT
.fi

The entry to remove must be prefixed with a dash, and the host name and port
number must exactly match what was added previously.
.SH DEFAULT
NULL
.SH PROTOCOLS
All
.SH EXAMPLE
.nf
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);
.fi
.SH 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.
.SH RETURN VALUE
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
.SH "SEE ALSO"
.BR CURLOPT_IPRESOLVE "(3), " CURLOPT_DNS_CACHE_TIMEOUT "(3), "
.BR CURLOPT_CONNECT_TO "(3), "