PPPoE support

A GTPv2 session or GTPv1 PDP context is set up when PPPoE session authentication includes any GTP parameters. The GTP session provides the IPv4 and IPv6 address to be used for the connecting host. IPCP and IPv6CP with SLAAC are supported to signal these addresses to the client. Only a single PPPoE session is supported per GTP subscriber. Additionally, DNS and NBNS can be signaled via GTP (A)PCO and reflected in IPCP, SLAAC, and stateless DHCPv6. Control plane packets such as ICMPv6 RS are always terminated on the BNG and are not forwarded over GTP.