Modify transit XDP to fork action based on gateway check

[pdgetrf]

The transit XDP on the gateway host behaves differently from it on none-gateway hosts. This host is to add the code to split function based on whether the XDP is on the gateway or not.

Determine whether we are on a gateway

if (pkt->ip->daddr == gateway_host_ip) {
...
}

gateway_host_ip is obtained from work in #63.

On the gateway host

• If pkt is a valid geneve pkt

• [x] If dst ip is internal, process as usual. This is assuming gateway host could also run normal pods. Gateway host will not be bouncer or divider of internal subnets but still could accept traffic destined to pods.
• [x] If dst ip is external (remote subnet), send to user space

• [x] if src ip is not a valid geneve pkt (e.g. sent from another gateway), pass pkt to user space

  • this is done already by XDP

On none-gateway host ("Muggle" host)

• works as normal Mizar

[pdgetrf]

pending #63 for actual control plane data to use