CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DOH_SSL_VERIFYHOST, long verify);
This option is the DOH equivalent of CURLOPT_SSL_VERIFYHOST(3) and only affects requests to the DOH server.
When CURLOPT_DOH_SSL_VERIFYHOST(3) is 2, the SSL certificate provided by the DOH server must indicate that the server name is the same as the server name to which you meant to connect to, or the connection fails.
Curl considers the DOH server the intended one when the Common Name field or a Subject Alternate Name field in the certificate matches the host name in the DOH URL to which you told Curl to connect.
When the verify value is set to 1L it is treated the same as 2L. However for consistency with the other VERIFYHOST options we suggest use 2 and not 1.
When the verify value is set to 0L, the connection succeeds regardless of the names used in the certificate. Use that ability with caution!
See also CURLOPT_DOH_SSL_VERIFYPEER(3) to verify the digital signature of the DOH server certificate. If libcurl is built against NSS and CURLOPT_DOH_SSL_VERIFYPEER(3) is zero, CURLOPT_DOH_SSL_VERIFYHOST(3) is also set to zero and cannot be overridden.
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
curl_easy_setopt(curl, CURLOPT_DOH_URL, "https://cloudflare-dns.com/dns-query");
/* Disable host name verification of the DOH server */
curl_easy_setopt(curl, CURLOPT_DOH_SSL_VERIFYHOST, 0L);
curl_easy_perform(curl);
}