version 2026-02-12
                        sshd             sshd
                          |               |
          sshd            | +-------------+
            \             | |
             +          remote(for client 2001)
             |                 |
         remote(client 2000)   +
              \               /
               \             +
                +------+     |
                        \    |
                     8000\   |8000
                          central
                     8001/   |8001
                    +---+    +
                   /          \
                  /           |6143 (port chosen by kernel)
             client          client
                 \2000         |  \2001
                  +---+        |   \
                       \       |    \4321 (port chosen by kernel)
                        ssh    |    ssh
                               |
                             ssh

central always listens port 8001

1 - client starts, creates KEY, connects to central, sends KEY to central, waits for remote
2 - central opens port 8000, waits for remote
3 - remote connects to central on port 8000, sends KEY, if wrong key, central kills connection
    (remote AND client will need to restart)
4 - central creates a link between remote and client
6 - client/remote connected


when ssh happens on client (kernel chooses port xx for ssh source port):

1 - client sends [<port xx> 0] to remote
2 - remote creates a tcp socket (let's call it RS) to 127.0.0.1 port 22
3 - all data from RS on remote is sent to client as [<port xx> <length> <data>]
    and all data from client to remote is sent on RS socket, same format
4 - when remote socket RS dies remote sends [<port xx> -1] to client
  - when ssh on client is killed, client sends [<port xx> -1] to remote
5 - the end receiving [<port xx> -1] kills the ssh central link, deletes link

when remote-central link dies, central kills client-central corresponding link
and vice-versa

messages:
[<port xx> 0] : <port xx> is an integer, 0 too
[<port xx> -1] : <port xx> is an integer, -1 too
[<port xx> <length> <data>]: <port xx> and <length> are integers, <data> is a buffer of
                             bytes, length of buffer: <length>
Integers are sent as 32 bits, little endian.