work on packet processing

libsrt/src/tunnel.rs

@@ -1,12 +1,92 @@
+use std::error::Error;
 use std::net::SocketAddr;
 use rand::rngs::OsRng;
 use x25519_dalek::{EphemeralSecret, PublicKey};
 use crate::cryptography::HASH;
+use crate::packets::clientbound::{ChannelInUsePacket, ChannelNotReadyPacket, ChannelReadyPacket};
+use crate::packets::initbound::HandshakeStartPacket;
+use crate::packets::recvbound::{EncryptedDataPacket, HandshakeResponsePacket};
+use crate::packets::relaybound::RelayDataPacket;
+use crate::packets::SRTPacket;
+
+// so we should have a method to handle each of the different types of packets
+
+// lets plan out the state machine?
+
+// State = NotConnected
+// ... => Ignore // we should not be receiving packets if we are not connected to the relay
+// <connect to relay> => State = Connected
+
+// State = Connected
+// ... => Ignore // even if we are connected to the relay, we havent sent init yet so shouldnt be recv anything
+// <send ChannelWait> => State = SentChannelWait
+
+// State = SentChannelWait
+// ChannelReady(init) => State = TunnelSendInit
+// ChannelReady(recv) => State = TunnelWaitForInit
+// ChannelNotReady => Wait for ChannelReady
+// ... => Ignore
+
+// State = TunnelSentInit
+// ChannelNotReady => State = Connected // receiving a ChannelNotReady while a tunnel is active indicates the other side disconnected
+// ... => Ignore
+// <send HandshakeStart> => State = TunnelWaitForResp
+
+// State = TunnelWaitForInit
+// HandshakeStart => State = TunnelSendHandshakeResponse
+// ChannelNotReady => State = Connected
+// ... => Ignore
+
+// State = TunnelWaitForResp
+// HandshakeResponse => State = Active
+// ChannelNotReady => State = Connected
+// ... => Ignore
+
+// State => TunnelSendHandshakeResponse
+// ChannelNotReady => State = Connected
+// ... => Ignore
+// <send HandshakeResponse> => State = Active
+
+// State => Active
+// EncryptedData => <process>
+// ChannelNotReady => State = Connected
+// ... => Ignore
+
+// something like this?
+// i think this covers every possible situation that the system could be in
+// i cannot think of others so good enough
+pub enum SPTunnelState {
+    TunnelNeedToSendChannelWait,
+    TunnelInUse,
+    TunnelSentChannelWaitWaitingForPartner,
+
+    TunnelNeedToSendInit,
+    TunnelSentInit,
+    TunnelWaitForResp,
+
+    TunnelWaitForInit,
+    TunnelNeedToSendHandshakeResponse,
+    TunnelSentHandshakeResponse,
+
+    Active
+}
+
+// keeping this for reference
+
+// so i guess we should go through each of these and make a function that implements that logic
+// we should make a function to handle every packet type we could receive, and then match the current state to figure out what to do
+// (arbitrary decision) match type then handle based on state, or check state then analyse packet?
+
+// like, say the recv loop parses a RelayData packet
+// it would then call .recv_relay_data() on the SPTunnel, which will decide what to do with that packet based on the current internal state of the tunnel
+// ok, so check pkt type first
+// then we need one big switch-case
+// each packet type gets its own function; parsing it from bytes into the struct form is done in the receive loop
+// so we should make .recv_relay_data(), .recv_encrypted_data(), etc
+// right
 
 /// The main tunnel state machine container
 pub struct SPTunnel {
-    relay: SocketAddr,
-    channel_name: String,
     pmk: [u8; 32],
     cid: [u8; 32],
 
@@ -14,10 +94,13 @@ pub struct SPTunnel {
     ee: PublicKey,
     eer: PublicKey,
 
-    state: SPTunnelState
+    state: SPTunnelState,
+
+    we_are_initializer: bool
 }
 impl SPTunnel {
-    fn new(relay: SocketAddr, channel_name: String) -> Self {
+    fn new(channel_name: String) -> Self {
+        let state = SPTunnelState::TunnelNeedToSendChannelWait;
         // calculate the pmk and cid (various hashes of the channel name)
         let pmk = HASH(&channel_name);
         let cid = HASH(&pmk);
@@ -27,18 +110,66 @@ impl SPTunnel {
         let ee = PublicKey::from(&e);
 
         SPTunnel {
-            relay,
-            channel_name,
             pmk,
             cid,
             e,
             ee,
+            we_are_initializer: false,
             eer: PublicKey::from([0u8; 32]),
             state: SPTunnelState::NotConnected,
         }
     }
+
+    /** FROM-RELAY Packets (us <- relay) **/
+    fn recv_channel_not_ready(&mut self, pkt: &ChannelNotReadyPacket) {
+        if pkt.channel != self.cid {
+            return; // ignore this packet, it isnt for us
+        }
+
+        // regenerate eph keys
+        self.e = EphemeralSecret::new(OsRng);
+        self.ee = PublicKey::from(&self.e);
+
+        self.state = SPTunnelState::TunnelSentChannelWaitWaitingForPartner;
+    }
+    fn recv_channel_ready(&mut self, pkt: &ChannelReadyPacket) {
+        if pkt.channel != self.cid {
+            return; // ignore this packet, it isnt for us
+        }
+        if pkt.you_are_initializer {
+            self.we_are_initializer = true;
+            self.state = SPTunnelState::TunnelNeedToSendInit;
+        } else {
+            self.we_are_initializer = false;
+            self.state = SPTunnelState::TunnelWaitForInit;
+        }
+    }
+    fn recv_channel_in_use(&mut self, pkt: &ChannelInUsePacket) {
+        if pkt.channel != self.cid {
+            return; // ignore this packet, it isnt for us
+        }
+        // we cant use this channel right now; set our state to reflect that
+        self.state = SPTunnelState::TunnelInUse;
+    }
+    fn recv_channel_relay_data(&mut self, pkt: &RelayDataPacket) {
+        if pkt.channel != self.cid {
+            return;
+        }
+        // we need to deencapsulate the packet and hand it BACK to the packet parse loop to be sent back to us and parse
+
+    }
+
+    /** VIA-RELAY Packets (us <--relay--< them)  **/
+    fn recv_handshake_start(&mut self, pkt: &HandshakeStartPacket) {
+    }
+    fn recv_handshake_response(&mut self, pkt: &HandshakeResponsePacket) {
+    }
+    fn recv_encrypted_data(&mut self, pkt: &EncryptedDataPacket) {
+    }
+
+    // State = Connected
+// ... => Ignore // even if we are connected to the relay, we havent sent init yet so shouldnt be recv anything
+// <send ChannelWait> => State = SentChannelWait
+
 }
 
-pub enum SPTunnelState {
-    NotConnected
-}