title: Redirecting non-SNI browsers to HTTP-only warning page in nginx
body: <p>When using an SNI-only certificate (Let's Encrypt, CloudFlare free), users who are using Windows XP with Chrome or IE are <a href="https://github.com/letsencrypt/letsencrypt/issues/1660" rel="nofollow">not able to connect to your site</a>. Firefox on XP works fine.</p>
  
  <p>I would like to test if the user agent is Chrome on XP or IE on XP (or anything on XP which is not Firefox), and redirect them to a HTTP warning page which tells them to use Firefox on XP.</p>
  
  <p>How would you do that under nginx?</p>
  
  <p>At the moment, I'm using this block to redirect all http links to https.</p>
  
  <pre><code>if ($http_cf_visitor ~ '{"scheme":"http"}') {
      return 301 https://$server_name$request_uri;
  }
  </code></pre>
  
  <p>How can I combine the above user agent detection into this block so non-SNI users are redirected to a HTTP only warning page?</p>