Tribblix: manual page: CURLOPT

CURLOPT_RESOLVE(3) Introduction to Library Functions CURLOPT_RESOLVE(3)

NAME

CURLOPT_RESOLVE - provide custom hostname 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 hostname 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.

libcurl does not copy the list, it needs to be kept around until
after the transfer has completed.

Each resolve rule to add should be written using the format

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

HOST is the name libcurl wants 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.

Specify the host as a single asterisk (*) to match all names. This
wildcard is resolved last so any resolve with a specific host and
port number is given priority.

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

The optional leading plus (+) specifies that the new entry should
timeout. Entries added without the leading plus character never
times out whereas entries added with +HOST:... times out just like
ordinary DNS cache entries.

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

An ADDRESS provided by this option is only 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 hostname
and port number must exactly match what was added previously.

Using this option multiple times makes the last set list override the
previous ones. Set it to NULL to disable its use again.

DEFAULT

NULL

PROTOCOLS

This functionality affects all supported protocols

EXAMPLE

int main(void)
{
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);
}

HISTORY

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.

AVAILABILITY

Added in curl 7.21.3

RETURN VALUE

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error
occurred, see libcurl-errors(3).