What applications would be expected to setup a network interface "stf0" and "gif0"
Those are Tunnel-Interfaces. They are commonly used to provide IPv6- or VPN-Services. They are usually always active, but not connected unless you set up your system to use them. 

You can determine if an interface is enabled but not active by observing its flags using ifconfig &lt;interfacename&gt; to not contain UP. 

You can look up the definition for those interfaces on the terminal with man gif or man stf, respectively.