title: WebSocket not working with HAProxy in tcp mode
body: <p>Consider this <code>HAProxy</code> configuration here:</p>
  <pre><code>global
      chroot /var/lib/haproxy
      user haproxy
      group haproxy
  
  defaults
      timeout connect 10s
      timeout client 50s
      timeout server 50s
  
  frontend fe_https_tomcat
      mode tcp
      bind *:443 ssl crt /path/cert.pem alpn h2,http/1.1
      default_backend be_tomcat
  
  backend be_tomcat
      mode tcp
      server localhost localhost:8081 check
  </code></pre>
  <p>The issue I have is that WebSocket do not seem to get through. My guess was that in tcp mode everything would pass through. Looks like it doesn't ... :-)</p>
  <p>The server responds with an error <code>403</code> when the WebSocket connection is getting established.</p>
  <p>Note that with the following http-mode setup, the WebSocket just works:</p>
  <pre><code>frontend fe_http_8080
      mode http
      bind *:8080
      default_backend be_tomcat_8080
  
  backend be_tomcat_8080
      mode http
      server localhost localhost:8081 check
  </code></pre>
  <p>Note that I need tcp-mode to have http/2 working.</p>