feat: pool and multiplex relay-to-relay tcp channels

common/src/protocol.rs

@@ -57,6 +57,30 @@ pub struct RelayForwardPrelude {
     pub initial_data: Vec<u8>,
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct R2rStreamData {
+    pub session_id: String,
+    pub stream_id: String,
+    pub data: Vec<u8>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct R2rStreamClosed {
+    pub session_id: String,
+    pub stream_id: String,
+    pub reason: Option<String>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(tag = "type", content = "data")]
+pub enum R2rFrame {
+    Open(RelayForwardPrelude),
+    Data(R2rStreamData),
+    Close(R2rStreamClosed),
+    Ping,
+    Pong,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 #[serde(tag = "type", content = "data")]
 pub enum ClientFrame {