title: SSL_CTX_set_verify with NULL verify_callback
body: <p>In openSSL I used function <a href="https://www.openssl.org/docs/manmaster/man3/SSL_CTX_set_verify.html" rel="nofollow noreferrer">SSL_CTX_set_verify</a> with <code>verify_mode= SSL_VERIFY_PEER</code> and <code>verify_callback= NULL</code> .</p>
  <p>What does it mean? The client will verify the server certificates chain or not?</p>