Escaping NAT using a reverse proxy

[Akilan1999]

Abstract

We focus here on escaping NAT for the project P2PRC. The intial plan is to use a middle server with an IPV4 address to escape NAT. The future plan would be to use a WebRTC approach to where we use a middle server to intansiate a direct p2p connection using UDP sockets with nodes behind NAT.

Architecture plan

The server behind NAT would use a reverse proxy server with an IPV4 address to be a possible way to communicate with the outside world.

Ex:

        NAT
         |
Server  <--> Reverse Proxy server with <--> Clients 
         |   public IPV4

We use the libaray known as frp. "frp is A fast reverse proxy to help you expose a local server behind a NAT or firewall to the internet."

The server behind the NAT IPTable would be broadcasted through the reverse proxy. The mapping would be done automatically though P2PRC because the reverse proxy could have certain ports already taken.

We are introducting a new concept of detecting reverse proxies over P2PRC. We call this reverse_proxy_server.json and reverse_proxy_mapping.json. The reverse_proxy_server.json file is incharge of detecting all reverse proxy servers and the reverse_proxy_mapping.json is incharge of logging all the reverse proxy server mappings talking place.

reverse_proxy_server.json

{
   "reverse_proxy_servers": [
           {
                   "Server_name": <server name>,
                   "Address": <remote address>,
                   "Latency": <latency>
           }, ... n
   ]
}

reverse_proxy_mapping.json

{
   "reverse_proxy_mappings": [
           {
                   "Server_name": <server name>,
                   "Address": <remote address>,
                   "Type": <TCP or UDP>,
                   "blind_port": <port no>
           }, ... n
   ]
}

Port allocation

The function for port allocation would need certain modifications need to ensure that the port is not only free on the server but also on the on reverse proxy server. We are debate on this would occur as it requires further reading on the inner depths of frp. The idea scenario would be that the odds a 5 or 6 digit taken is a low probability.

How would the ip tables would look

There would not be much change when a client looks at it. This only difference is that the client see's the address of the proxy server.

Ex:

{
 "ip_address": [
  {
   "ipv4": "<reverse proxy address>",
   "ipv6": "",
   "latency": 0,
   "download": 0,
   "upload": 0,
   "serverport": "<server port no>"
  }
 ]
}

If the server is using a reverse proxy then the server port no should be decided by P2PRC to ensure that there is no scenario where the port is already taken.

New Cli Commands

We will be introducing a new set of Cli commands. These cli commands would be incharge to starting the reverse proxy or connecting to the reverse proxy and various other function.

1. start reverse proxy (need public IPV4)

   p2prc -s --reverse-proxy

   This will start the reverse and autoamtically broadcast as a reverse proxy as well.

2. connecting to a reverse proxy

   p2prc -s --connect-reverse-proxy <proxy ip address>

   This will start p2prc as server and automatically set the server port and link it to the reverse proxy and any connections would go through the reverse proxy.

3. Listing all proxy servers avaliable

   p2prc --view-rps or p2prc --view-reverse-proxy-servers

4. Listing all reverse proxy connection mapping

   p2prc --view-rpm or p2prc --view-reverse-proxy-mapping 

source: https://akilan.io/technicalposts/p2prc-escaping-nat/