feat(p2p): mesh stack, LoRa mock transport, and relay demo

Implement transport abstraction (TCP/iroh), announce and routing table,
multi-hop mesh router, truncated-address link layer, and LoRa mock
medium with fragmentation plus EU868-style duty-cycle accounting.
Add mesh_lora_relay_demo and scripts/mesh-demo.sh. Relax CBOR vs JSON
size assertion to match fixed-size cryptographic overhead. Extend
.gitignore for nested targets and node_modules.

Made-with: Cursor

crates/quicprochat-p2p/src/transport_manager.rs

@@ -0,0 +1,181 @@
+//! Multi-transport manager for routing packets across different backends.
+//!
+//! The [`TransportManager`] holds multiple [`MeshTransport`] implementations
+//! and selects the best one for a given [`TransportAddr`] variant.
+//!
+//! [`crate::transport_lora::LoRaTransport`] performs MTU-aware fragmentation internally; use
+//! [`crate::transport_lora::split_for_mtu`] only when chunking at a higher layer.
+
+use anyhow::{bail, Result};
+
+use crate::transport::{MeshTransport, TransportAddr, TransportInfo};
+
+/// Manages multiple mesh transports and routes packets to the best available one.
+pub struct TransportManager {
+    transports: Vec<Box<dyn MeshTransport>>,
+}
+
+impl TransportManager {
+    /// Create an empty transport manager.
+    pub fn new() -> Self {
+        Self {
+            transports: Vec::new(),
+        }
+    }
+
+    /// Register a transport backend.
+    pub fn add(&mut self, transport: Box<dyn MeshTransport>) {
+        self.transports.push(transport);
+    }
+
+    /// Send data, choosing the best transport for the given address type.
+    ///
+    /// The selection heuristic matches the [`TransportAddr`] variant to the
+    /// transport whose name corresponds to that variant (iroh for `Iroh`,
+    /// tcp for `Socket`, etc). Falls back to trying each transport in order.
+    pub async fn send(&self, dest: &TransportAddr, data: &[u8]) -> Result<()> {
+        let target_name = match dest {
+            TransportAddr::Iroh(_) => "iroh-quic",
+            TransportAddr::Socket(_) => "tcp",
+            TransportAddr::LoRa(_) => "lora",
+            TransportAddr::Serial(_) => "serial",
+            TransportAddr::Raw(_) => "",
+        };
+
+        // First, try the transport whose name matches the address type.
+        for t in &self.transports {
+            if t.info().name == target_name {
+                return t.send(dest, data).await;
+            }
+        }
+
+        // Fallback: try each transport in order until one succeeds.
+        let mut last_err = None;
+        for t in &self.transports {
+            match t.send(dest, data).await {
+                Ok(()) => return Ok(()),
+                Err(e) => last_err = Some(e),
+            }
+        }
+
+        match last_err {
+            Some(e) => Err(e),
+            None => bail!("no transports registered"),
+        }
+    }
+
+    /// List all registered transports.
+    pub fn transports(&self) -> &[Box<dyn MeshTransport>] {
+        &self.transports
+    }
+
+    /// Get info for all registered transports.
+    pub fn transport_info(&self) -> Vec<TransportInfo> {
+        self.transports.iter().map(|t| t.info()).collect()
+    }
+
+    /// Shut down all transports.
+    pub async fn close_all(&self) -> Result<()> {
+        for t in &self.transports {
+            t.close().await?;
+        }
+        Ok(())
+    }
+}
+
+impl Default for TransportManager {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::transport::TransportPacket;
+
+    /// A mock transport that accepts any send and returns a fixed name.
+    struct MockTransport {
+        name: String,
+    }
+
+    impl MockTransport {
+        fn new(name: &str) -> Self {
+            Self {
+                name: name.to_string(),
+            }
+        }
+    }
+
+    #[async_trait::async_trait]
+    impl MeshTransport for MockTransport {
+        fn info(&self) -> TransportInfo {
+            TransportInfo {
+                name: self.name.clone(),
+                mtu: 1500,
+                bitrate: 1_000_000,
+                bidirectional: true,
+            }
+        }
+
+        async fn send(&self, _dest: &TransportAddr, _data: &[u8]) -> Result<()> {
+            Ok(())
+        }
+
+        async fn recv(&self) -> Result<TransportPacket> {
+            bail!("MockTransport does not support recv")
+        }
+    }
+
+    #[tokio::test]
+    async fn routes_socket_to_tcp() {
+        let mut mgr = TransportManager::new();
+        mgr.add(Box::new(MockTransport::new("tcp")));
+        mgr.add(Box::new(MockTransport::new("iroh-quic")));
+
+        let addr = TransportAddr::Socket("127.0.0.1:8080".parse().unwrap());
+        let result = mgr.send(&addr, b"test data").await;
+        assert!(result.is_ok());
+    }
+
+    #[tokio::test]
+    async fn routes_iroh_to_iroh_transport() {
+        let mut mgr = TransportManager::new();
+        mgr.add(Box::new(MockTransport::new("tcp")));
+        mgr.add(Box::new(MockTransport::new("iroh-quic")));
+
+        let addr = TransportAddr::Iroh(vec![0xAA; 32]);
+        let result = mgr.send(&addr, b"test data").await;
+        assert!(result.is_ok());
+    }
+
+    #[tokio::test]
+    async fn no_transports_returns_error() {
+        let mgr = TransportManager::new();
+        let addr = TransportAddr::Socket("127.0.0.1:8080".parse().unwrap());
+        let result = mgr.send(&addr, b"data").await;
+        assert!(result.is_err());
+    }
+
+    #[tokio::test]
+    async fn transport_info_lists_all() {
+        let mut mgr = TransportManager::new();
+        mgr.add(Box::new(MockTransport::new("tcp")));
+        mgr.add(Box::new(MockTransport::new("iroh-quic")));
+
+        let infos = mgr.transport_info();
+        assert_eq!(infos.len(), 2);
+        assert_eq!(infos[0].name, "tcp");
+        assert_eq!(infos[1].name, "iroh-quic");
+    }
+
+    #[tokio::test]
+    async fn close_all_succeeds() {
+        let mut mgr = TransportManager::new();
+        mgr.add(Box::new(MockTransport::new("tcp")));
+        mgr.add(Box::new(MockTransport::new("iroh-quic")));
+
+        let result = mgr.close_all().await;
+        assert!(result.is_ok());
+    }
+}