Devices with static WAN IP address needn't ping to a Super Node

[photosssa]

Discussed in #76

^{Originally posted by photosssa January 3, 2023}

If a device connected to ethernet with NAT, to establish a P2P connection to this device from any device, Super Node(SN) is needed;

• Device got its WAN IP address with NAT from ping/pong with a SN;
• Device keep its WAN IP address alive with ping/pong with a SN continuously;
• Device got a handshake transited from SN for NAT may drop packet from IP addresses without a former deliver record;

If a device has static WAN IP address, means:

• Device administrator knows its WAN IP address;
• Device WAN IP address keeps unchanged(static);
• Packets from any location sent to this WAN IP address reaches;
  SN is no more needed to establish a connection to devices with static WAN address;

How to config WAN IP address and no pinging SN in CYFS

Config endpoints for CYFS Stack

1. Device has WAN IP address (without NAT): Config this WAN address for CYFS stack, socket bound to this WAN address;
2. Device has a mapped static WAN IP address(with NAT):

• Config both local address and its mapped WAN address for CYFS stack, socket bound to local address
• Config local address and a its mapped port for CYFS stack, socket bound to local address, then ping/pong with SN once, got its mapped WAN address combining WAN IP and mapped port;

Config optional super nodes for CYFS stack

• Config optional super nodes for CYFS stack, select one or more SN from those to ping/pong with;
• If device needn't SN, config an empty optional super nodes; but CYFS stack need other ways to announce its endpoints(i.e. static configed known device; object Key-value storage on block chain);

Config known super nodes for CYFS stack

1. To establish a connection from device with static WAN address to other devices, target device's pinging SN is still needed;
2. Config known super nodes for CYFS stack to find target device's ping SN in those; it differs from optional super nodes;

[lurenpluto]

Support for NO-SN mode has been added, see the issue below
cyfs-stack support NO-SN online#56