title: "Sign in to Wi-Fi Network" never happens on Android devices, but redirection works fine
body: <p>I have a Captive Portal setup using RadiusDesk + FreeRADIUS + CoovaChilli + Nginx.</p>
  
  <p>Redirection works 100% on any device (including Android). If the user is not yet authenticated, when they attempt to go to any http:// webpage, they get redirected to my captive portal "login" page as expected.</p>
  
  <p>Here's where I'm struggling to understand the difference:</p>
  
  <ul>
  <li>on iOS devices, the moment you connect to this Wifi, the popup for "Log in" appears immediately (as expected) and it is going to my captive portal login page</li>
  <li>on Android devices you can connect to the Wifi, but nothing further happens. If you try to browse, you do get redirected, but where is the "Sign in to Wi-Fi network" popup?</li>
  </ul>
  
  <p>Even more suspicious, we have a Captive Portal (this one is a proprietary "Cyberoam" system) here in our office, and when I use the same Android devices to connect to <em>that</em> network over Wifi, I immediately get the "Sign in to Wi-Fi network" popup as expected. What's up with my setup?</p>
  
  <p>Here is my current <code>/etc/coova/config</code> setup:</p>
  
  <pre><code>HS_LANIF=eth2              # Subscriber Interface for client devices
  HS_NETWORK=10.1.1.0        # HotSpot Network (must include HS_UAMLISTEN)
  HS_NETMASK=255.255.255.0     # HotSpot Network Netmask
  HS_UAMLISTEN=10.1.1.1      # HotSpot IP Address (on subscriber network)
  HS_UAMPORT=3990            # HotSpot UAM Port (on subscriber network)
  HS_UAMUIPORT=4990          # HotSpot UAM "UI" Port (on subscriber network, for embedded portal)
  HS_NASID=localhost
  HS_RADIUS=localhost
  HS_RADIUS2=localhost
  HS_RADSECRET=testing123    # Set to be your RADIUS shared secret
  HS_UAMSECRET=greatsecret     # Set to be your UAM secret
  HS_UAMALIASNAME=chilli
  HS_SSID="Struisbaai"
  HS_NASIP=127.0.0.1    # To explicitly set NAS-IP-Address
  HS_UAMSERVER=$HS_UAMLISTEN
  HS_UAMFORMAT=http://\$HS_UAMLISTEN/cake2/rd_cake/dynamic_details/chilli_browser_detect/
  HS_MACAUTH=on              # To turn on MAC Authentication
  HS_TCP_PORTS="80 23 8000"
  HS_MODE=hotspot
  HS_TYPE=chillispot
  HS_WWWDIR=/etc/chilli/www
  HS_WWWBIN=/etc/chilli/wwwsh
  HS_PROVIDER=Coova
  HS_PROVIDER_LINK=http://www.coova.org/
  HS_LOC_NAME="My HotSpot"           # WISPr Location Name and used in portal
  HS_COAPORT=3799
  </code></pre>
  
  <p>I also notice that if I connect with a PC to my hostpot network, I can <code>ping clients3.google.com</code> and get a response (before authentication!) which should not be possible. All other domains get no response (as expected). This would explain why the Android devices think they "have an internet connection", but nowhere do I whitelist this domain in my CoovaChilli configuration as far as I can tell...</p>