CURLOPT_DOH_URL - Man Page

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 * to a null-terminated string which must be URL-encoded in the following format: "https://host:port/path". It MUST specify an 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) will still return 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 will use the default name lookup function. You can bootstrap that by providing the address for the DoH server with CURLOPT_RESOLVE(3).

Disable DoH use again by setting this option to NULL.

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 - there is no default DoH URL. If this option is not set, libcurl will use the default name resolver.

Protocols

All

Example

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 7.62.0

Return Value

Returns CURLE_OK on success or CURLE_OUT_OF_MEMORY if there was insufficient heap space.

Note that curl_easy_setopt(3) will not 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.

See Also

CURLOPT_VERBOSE(3), CURLOPT_RESOLVE(3),

Referenced By

curl_easy_setopt(3), CURLOPT_SSL_CTX_FUNCTION(3).

May 17, 2022 libcurl 7.86.0 curl_easy_setopt options