Tribblix: manual page: CURLOPT_DOH

CURLOPT_DOH_URL(3) Introduction to Library Functions CURLOPT_DOH_URL(3)

NAME

CURLOPT_DOH_URL - provide the DNS-over-HTTPS URL

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DOH_URL, char *URL);

DESCRIPTION

Pass in a pointer to a URL for the DoH server to use for name
resolving. The parameter should be a char pointer to a
null-terminated string which must be a valid and correct HTTPS URL.

libcurl does not validate the syntax or use this variable until the
transfer is issued. Even if you set a crazy value here,
curl_easy_setopt(3) still returns CURLE_OK.

curl sends POST requests to the given DNS-over-HTTPS URL.

To find the DoH server itself, which might be specified using a name,
libcurl uses the default name lookup function. You can bootstrap that
by providing the address for the DoH server with CURLOPT_RESOLVE(3).

The application does not have to keep the string around after setting
this option.

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

INHERIT OPTIONS

DoH lookups use SSL and some SSL settings from your transfer are
inherited, like CURLOPT_SSL_CTX_FUNCTION(3).

The hostname and peer certificate verification settings are not
inherited but can be controlled separately via
CURLOPT_DOH_SSL_VERIFYHOST(3) and CURLOPT_DOH_SSL_VERIFYPEER(3).

A set CURLOPT_OPENSOCKETFUNCTION(3) callback is not inherited.

KNOWN BUGS

Even when DoH is set to be used with this option, there are still
some name resolves that are performed without it, using the default
name resolver mechanism. This includes name resolves done for
CURLOPT_INTERFACE(3), CURLOPT_FTPPORT(3), a proxy type set to
CURLPROXY_SOCKS4 or CURLPROXY_SOCKS5 and probably some more.

DEFAULT

NULL

PROTOCOLS

This functionality affects all supported protocols

EXAMPLE

int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
curl_easy_setopt(curl, CURLOPT_DOH_URL, "https://dns.example.com");
curl_easy_perform(curl);
}
}

AVAILABILITY

Added in curl 7.62.0

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).

Note that curl_easy_setopt(3) does immediately parse the given string
so when given a bad DoH URL, libcurl might not detect the problem
until it later tries to resolve a name with it.