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curl/docs/libcurl/opts/CURLOPT_IPRESOLVE.3
Lucas Clemente Vella 84d2839740
CURLOPT_IPRESOLVE: preventing wrong IP version from being used
In some situations, it was possible that a transfer was setup to
use an specific IP version, but due do DNS caching or connection
reuse, it ended up using a different IP version from requested.

This commit changes the effect of CURLOPT_IPRESOLVE from simply
restricting address resolution to preventing the wrong connection
type being used, when choosing a connection from the pool, and
to restricting what addresses could be used when establishing
a new connection.

It is important that all addresses versions are resolved, even if
not used in that transfer in particular, because the result is
cached, and could be useful for a different transfer with a
different CURLOPT_IPRESOLVE setting.

Closes #6853
2021-05-20 16:58:31 +02:00

66 lines
2.3 KiB
Groff

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.TH CURLOPT_IPRESOLVE 3 "19 Jun 2014" "libcurl 7.37.0" "curl_easy_setopt options"
.SH NAME
CURLOPT_IPRESOLVE \- specify which IP protocol version to use
.SH SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_IPRESOLVE, long resolve);
.SH DESCRIPTION
Allows an application to select what kind of IP addresses to use when
establishing a connection or choosing one from the connection pool. This is
interesting when using host names that resolve addresses using more than
one version of IP. The allowed values are:
.IP CURL_IPRESOLVE_WHATEVER
Default, can use addresses of all IP versions that your system allows.
.IP CURL_IPRESOLVE_V4
Uses only IPv4 addresses.
.IP CURL_IPRESOLVE_V6
Uses only IPv6 addresses.
.SH DEFAULT
CURL_IPRESOLVE_WHATEVER
.SH PROTOCOLS
All
.SH EXAMPLE
.nf
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/foo.bin");
/* of all addresses example.com resolves to, only IPv6 ones are used */
curl_easy_setopt(curl, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V6);
ret = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
.fi
.SH AVAILABILITY
Always
.SH RETURN VALUE
Returns CURLE_OK
.SH "SEE ALSO"
.BR CURLOPT_HTTP_VERSION "(3), " CURLOPT_SSLVERSION "(3), "