init

crates/vpnshare-transport/src/lib.rs

@@ -0,0 +1,55 @@
+//! Transport abstraction for USB, Wi-Fi, and hotspot-local VSHP sessions.
+
+use std::io;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum TransportKind {
+    UsbAccessory,
+    WifiLan,
+    LocalOnlyHotspot,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct TransportDescriptor {
+    pub kind: TransportKind,
+    pub label: String,
+    pub mtu_hint: Option<u16>,
+}
+
+pub trait PacketTransport {
+    fn descriptor(&self) -> &TransportDescriptor;
+    fn send_frame(&mut self, bytes: &[u8]) -> io::Result<()>;
+    fn receive_frame(&mut self, buffer: &mut [u8]) -> io::Result<usize>;
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ResumeToken {
+    pub session_id: [u8; 16],
+    pub transport_generation: u64,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Backpressure {
+    pub queued_bytes: usize,
+    pub max_queue_bytes: usize,
+}
+
+impl Backpressure {
+    pub fn should_pause_reads(&self) -> bool {
+        self.queued_bytes >= self.max_queue_bytes
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn backpressure_pauses_when_queue_is_full() {
+        assert!(Backpressure {
+            queued_bytes: 1024,
+            max_queue_bytes: 1024,
+        }
+        .should_pause_reads());
+    }
+}