The roadwarriors carol and dave set up an IPv6 connection each
to gateway moon. The authentication is based on X.509 certificates.
Upon the successful establishment of the IPv6 ESP tunnels, leftfirewall=yes
automatically inserts ip6tables-based firewall rules that let pass the tunneled traffic.
In order to test both tunnel and firewall, both carol and dave send
an IPv6 ICMP request to the client alice behind the gateway moon
using the ping6 command.