docs: updated the TriBA docs to match the response update

docs/TrinitrixBackendAPI.md

@@ -1,5 +1,7 @@
 # Trinitrix Backend API (TriBA)
 
+**Disclaimer:** These docs are WIP and going to receive a lot of improvement.
+
 ## Basic concept
 
 The core starts a CBS as its child process and gives it as first Arg a base64 encoded UUID.
@@ -16,12 +18,29 @@ Post-Handshake communication is structured in packets, which have the following
 | 4            | uint32            | The size of the payload.                                           |
 | -            | encrypted payload | The AES-GCM-SIV encrypted MessagePack serialization of the packet. |
 
-A decrypted and deserialized packet looks like this:
+A decrypted and deserialized payload contains either a response or a request.
+A request looks as follows:
 
 | Size | Name   | Type   | Content                                                                                                           |
 |------|--------|--------|-------------------------------------------------------------------------------------------------------------------|
-| 8    | `id`   | uint64 | The ID of _this_ packet. Is expected to be an incrementing counter.                                               |
-| -    | `body` | enum   | The actual packet date. (this will be better documented, as soon, as I dive into the mPack serialization details) |
+| 8    | `id`   | uint64 | The ID of _this_ packet.                                                                                          |
+| -    | `body` | enum   | The actual packet data. (this will be better documented, as soon, as I dive into the mPack serialization details) |
+
+A response looks like this:
+
+| Size | Name   | Type   | Content                                               |
+|------|--------|--------|-------------------------------------------------------|
+| 8    | `id`   | uint64 | The ID of _this_ packet.                              |
+| 8    | `req`  | uint64 | The ID of the request packet this response refers to. |
+| -    | `body` | enum   | The actual packet data.                               |
+
+**Every request packet, that is sent over the socket, has to get a linked response packet.**
+
+### IDs
+
+Packet IDs are expected to be an incremental counter.
+There is no difference between requests and responses originating from the same socket side when it comes to IDs.
+So both - requests and responses - should share the same counter.
 
 ## Handshake
 
@@ -35,6 +54,8 @@ The handshaking process after connecting to the socket looks as follows:
 6. __Connection Upgrade:__ From this point on, all communication is structured by packets.
    The packet encryption key is calculated using x25519 Diffie-Hellman and the previously exchanged keys.
    The nonce from step 5 will be used as nonce for all packets.
-7. The CBS sends the `HandshakeUpgradeConnection` packet.
-8. (In here there is going to happen API version information exchange etc.)
-9. The Core responds with `HandshakeSuccess`
+7. The CBS sends the `Request::HandshakeUpgradeConnection` packet.
+8. The core responds with `Response::Success`.
+9. (In here there is going to happen API version information exchange etc.)
+10. The Core sends a `Request::HandshakeSuccess`
+11. The CBS responds with `Response::Succcess`

src/cbs/connection.rs

@@ -56,6 +56,8 @@ impl UnstableConnection {
         let packet = Packet::recv(&mut sock_rx, &cipher, &nonce).await?;
         match packet {
             Packet::Request { id, body } => {
+                match body {
+                    Request::HandshakeUpgradeConnection => {
                         Packet::response(id_pool.acquire(), id, Response::Success)
                             .send(&mut sock_tx, &cipher, &nonce)
                             .await?;
@@ -65,6 +67,11 @@ impl UnstableConnection {
                             id = self.id
                         );
                     }
+                    req => return Err(anyhow!(
+                        "expected cbs to send: Request::HandshakeUpgradeConnection, but got: Request::{req}"
+                    ))
+                }
+            }
             body => {
                 return Err(anyhow!(
                     "expected cbs to send: Request::HandshakeUpgradeConnection, but got: {body}"
@@ -72,6 +79,10 @@ impl UnstableConnection {
             }
         }
 
+        Packet::request(id_pool.acquire(), Request::HandshakeSuccess)
+            .send(&mut sock_tx, &cipher, &nonce)
+            .await?;
+
         // Poll packets from socket
         {
             let cipher = cipher.clone();