Research and consider implementing cass_cluster_set_use_hostname_resolution

[Lorak-mmk]

We removed it from cassandra.h because we saw no point in disabling hostname resolution.
However, the name is misleading.
Description of this:

 * Enable/Disable retrieving hostnames for IP addresses using reverse IP lookup.
 *
 * This is useful for authentication (Kerberos) or encryption (SSL) services
 * that require a valid hostname for verification.

So this is about reverse-lookup, not just DNS resolution.

It is also mentioned in description of cass_ssl_set_verify_flags:

/**
 * Sets verification performed on the peer's certificate.
 *
 * CASS_SSL_VERIFY_NONE - No verification is performed
 * CASS_SSL_VERIFY_PEER_CERT - Certificate is present and valid
 * CASS_SSL_VERIFY_PEER_IDENTITY - IP address matches the certificate's
 * common name or one of its subject alternative names. This implies the
 * certificate is also present.
 * CASS_SSL_VERIFY_PEER_IDENTITY_DNS - Hostname matches the certificate's
 * common name or one of its subject alternative names. This implies the
 * certificate is also present. Hostname resolution must also be enabled.
 *
 * <b>Default:</b> CASS_SSL_VERIFY_PEER_CERT
 *
 * @public @memberof CassSsl
 *
 * @param[in] ssl
 * @param[in] flags
 * @return CASS_OK if successful, otherwise an error occurred
 *
 * @see cass_cluster_set_use_hostname_resolution()
 */
CASS_EXPORT void
cass_ssl_set_verify_flags(CassSsl* ssl,
                          int flags);

We should verify again if this functionality really is something that we want to totally get rid of.

[wprzytula]

We removed it from cassandra.h because we saw no point in disabling hostname resolution.

No. I removed it from cassandra.h because I saw no use of the reverse IP lookup. It's nothing I ever heard about in the drivers, nor we do have that in Rust Driver.

[Lorak-mmk]

I get that. It doesn't yet mean that the functionality is useless. I'd like to better understand why it was present in the old driver.