Update troubleshooting docs to include iOS reconnection loop (trailof…

…bits#1042)

* Update troubleshooting docs to include iOS reconnection loop

* nits

docs/troubleshooting.md

@@ -18,6 +18,7 @@
      * [I can't get my router to connect to the Algo server](#i-cant-get-my-router-to-connect-to-the-algo-server)
      * [I can't get Network Manager to connect to the Algo server](#i-cant-get-network-manager-to-connect-to-the-algo-server)
      * [Various websites appear to be offline through the VPN](#various-websites-appear-to-be-offline-through-the-vpn)
+     * [Devices appear to be stuck in reconnection loop](#devices-appear-to-be-stuck-in-reconnection-loop)
      * ["Error 809" or IKE_AUTH requests that never make it to the server](#error-809-or-ike_auth-requests-that-never-make-it-to-the-server)
   * [I have a problem not covered here](#i-have-a-problem-not-covered-here)
 
@@ -213,6 +214,17 @@ $ sudo ifconfig wlan0 mtu 1438
 
 You can also set the `max_mss` variable to a new value in config.cfg, and then redeploy your server rather than reconfigure the current one in-place.
 
+### Clients appear stuck in a reconnection loop
+
+If you're using 'Connect on Demand' on iOS and your client device appears stuck in a reconnection loop after switching from WiFi to LTE or vice versa, you may want to try disabling DoS protection in strongSwan.
+
+The configuration value can be found in `/etc/strongswan.d/charon.conf`. After making the change you must reload or restart ipsec.
+
+Example command:
+```
+sed -i -e 's/#*.dos_protection = yes/dos_protection = no/' /etc/strongswan.d/charon.conf && ipsec restart
+```
+
 ### "Error 809" or IKE_AUTH requests that never make it to the server
 
 On Windows, this issue may manifest with an error message that says "The network connection between your computer and the VPN server could not be established because the remote server is not responding... This is Error 809." On other operating systems, you may try to debug the issue by capturing packets with tcpdump and notice that, while IKE_SA_INIT request and responses are exchanged between the client and server, IKE_AUTH requests never make it to the server.