testing: Add route-based/net2net-vti scenario

testing/tests/route-based/net2net-vti/description.txt

@@ -0,0 +1,12 @@
+A connection between the subnets behind the gateways <b>moon</b> and <b>sun</b>
+is set up using VTI interfaces.
+<p/>
+The gateways use <b>route-based forwarding</b> with <b>VTI tunnels</b>, with
+firewall rules to allow traffic to pass. The IPsec traffic selector used is
+0.0.0.0/0, however specific routing is achieved with routes on the VTI
+interfaces. The IKE daemon is configured to not install routes with
+<em>charon.install_routes=0</em>, and static routes are installed for the
+target subnets on the VTI interfaces.
+<p/>
+Client <b>alice</b> behind gateway <b>moon</b> pings client <b>bob</b> located
+behind gateway <b>sun</b>.