transport/ethernet: rename discovery module to neighbor

Rename the ethernet link-local neighbor-beacon subsystem from the
overloaded "discovery" vocabulary to a neighbor umbrella. The beacon
frame vocabulary is retained (build_beacon/parse_beacon/BEACON_SIZE/
FRAME_TYPE_BEACON/FRAME_TYPE_DATA); only the subsystem and buffer
identifiers change: DiscoveryBuffer becomes NeighborBuffer,
discovery_buffer becomes neighbor_buffer, and DISCOVERY_VERSION becomes
BEACON_VERSION (wire value 0x01 unchanged). Config toggles are left for
a follow-up commit. Behavior-neutral.

src/transport/ethernet/mod.rs

@@ -6,8 +6,8 @@
 //! 802.11 transparently on Linux).
 
 pub mod addr;
-pub mod discovery;
 pub mod io;
+pub mod neighbor;
 pub mod stats;
 
 pub use addr::parse_mac_string;
@@ -17,8 +17,8 @@ use super::{
     TransportId, TransportState, TransportType,
 };
 use crate::config::EthernetConfig;
-use discovery::{DiscoveryBuffer, FRAME_TYPE_BEACON, FRAME_TYPE_DATA, build_beacon, parse_beacon};
 use io::{AsyncPacketSocket, ETHERNET_BROADCAST, PacketSocket};
+use neighbor::{FRAME_TYPE_BEACON, FRAME_TYPE_DATA, NeighborBuffer, build_beacon, parse_beacon};
 use stats::EthernetStats;
 
 use secp256k1::XOnlyPublicKey;
@@ -56,8 +56,8 @@ pub struct EthernetTransport {
     /// (`[type:1][length:2 LE][payload]`). The 2-byte length field is required
     /// to trim NIC minimum-frame padding before AEAD verification.
     effective_mtu: u16,
-    /// Discovery buffer for discovered peers.
-    discovery_buffer: Arc<DiscoveryBuffer>,
+    /// Neighbor buffer for discovered peers.
+    neighbor_buffer: Arc<NeighborBuffer>,
     /// Transport-level statistics.
     stats: Arc<EthernetStats>,
     /// Node's public key for beacon construction.
@@ -73,7 +73,7 @@ impl EthernetTransport {
         packet_tx: PacketTx,
     ) -> Self {
         let interface = config.interface.clone();
-        let discovery_buffer = Arc::new(DiscoveryBuffer::new(transport_id));
+        let neighbor_buffer = Arc::new(NeighborBuffer::new(transport_id));
         let stats = Arc::new(EthernetStats::new());
 
         Self {
@@ -88,7 +88,7 @@ impl EthernetTransport {
             local_mac: None,
             interface,
             effective_mtu: 1499, // default, updated on start
-            discovery_buffer,
+            neighbor_buffer,
             stats,
             local_pubkey: None,
         }
@@ -164,7 +164,7 @@ impl EthernetTransport {
         let packet_tx = self.packet_tx.clone();
         let mtu = self.effective_mtu;
         let discovery_enabled = self.config.discovery();
-        let discovery_buffer = self.discovery_buffer.clone();
+        let neighbor_buffer = self.neighbor_buffer.clone();
         let stats = self.stats.clone();
         let recv_socket = socket.clone();
 
@@ -175,7 +175,7 @@ impl EthernetTransport {
                 packet_tx,
                 mtu,
                 discovery_enabled,
-                discovery_buffer,
+                neighbor_buffer,
                 stats,
             )
             .await;
@@ -368,7 +368,7 @@ impl Transport for EthernetTransport {
     }
 
     fn discover(&self) -> Result<Vec<DiscoveredPeer>, TransportError> {
-        Ok(self.discovery_buffer.take())
+        Ok(self.neighbor_buffer.take())
     }
 
     fn auto_connect(&self) -> bool {
@@ -391,7 +391,7 @@ async fn ethernet_receive_loop(
     packet_tx: PacketTx,
     mtu: u16,
     discovery_enabled: bool,
-    discovery_buffer: Arc<DiscoveryBuffer>,
+    neighbor_buffer: Arc<NeighborBuffer>,
     stats: Arc<EthernetStats>,
 ) {
     // Buffer with headroom: frame type prefix + MTU + some extra
@@ -449,11 +449,11 @@ async fn ethernet_receive_loop(
                         stats.record_beacon_recv();
 
                         if discovery_enabled && let Some(pubkey) = parse_beacon(&buf[..len]) {
-                            discovery_buffer.add_peer(src_mac, pubkey);
+                            neighbor_buffer.add_peer(src_mac, pubkey);
                             trace!(
                                 transport_id = %transport_id,
                                 remote_mac = %format_mac(&src_mac),
-                                "Discovery beacon received"
+                                "Neighbor beacon received"
                             );
                         }
                     }
@@ -735,6 +735,6 @@ mod tests {
 
     #[test]
     fn test_beacon_size() {
-        assert_eq!(discovery::BEACON_SIZE, 34);
+        assert_eq!(neighbor::BEACON_SIZE, 34);
     }
 }

src/transport/ethernet/neighbor.rs

@@ -1,18 +1,18 @@
-//! Ethernet LAN discovery via broadcast beacons.
+//! Ethernet LAN neighbor detection via broadcast beacons.
 //!
 //! Beacon format (34 bytes total):
-//! - `0x01` (1 byte): frame type = discovery announcement
-//! - `0x01` (1 byte): discovery protocol version
+//! - `0x01` (1 byte): frame type = neighbor beacon
+//! - `0x01` (1 byte): beacon protocol version
 //! - x-only public key (32 bytes): node's Nostr identity
 
 use crate::transport::{DiscoveredPeer, TransportAddr, TransportId};
 use secp256k1::XOnlyPublicKey;
 use std::sync::Mutex;
 
-/// Discovery protocol version.
-pub const DISCOVERY_VERSION: u8 = 0x01;
+/// Beacon protocol version.
+pub const BEACON_VERSION: u8 = 0x01;
 
-/// Frame type prefix for discovery announcement beacons.
+/// Frame type prefix for neighbor beacon frames.
 pub const FRAME_TYPE_BEACON: u8 = 0x01;
 
 /// Frame type prefix for FIPS data frames.
@@ -21,16 +21,16 @@ pub const FRAME_TYPE_DATA: u8 = 0x00;
 /// Total beacon payload size: type(1) + version(1) + pubkey(32).
 pub const BEACON_SIZE: usize = 34;
 
-/// Build a discovery announcement beacon payload.
+/// Build a neighbor beacon payload.
 pub fn build_beacon(pubkey: &XOnlyPublicKey) -> [u8; BEACON_SIZE] {
     let mut buf = [0u8; BEACON_SIZE];
     buf[0] = FRAME_TYPE_BEACON;
-    buf[1] = DISCOVERY_VERSION;
+    buf[1] = BEACON_VERSION;
     buf[2..BEACON_SIZE].copy_from_slice(&pubkey.serialize());
     buf
 }
 
-/// Parse a discovery announcement beacon payload.
+/// Parse a neighbor beacon payload.
 ///
 /// Returns the sender's public key, or None if the payload is invalid.
 pub fn parse_beacon(data: &[u8]) -> Option<XOnlyPublicKey> {
@@ -40,20 +40,20 @@ pub fn parse_beacon(data: &[u8]) -> Option<XOnlyPublicKey> {
     if data[0] != FRAME_TYPE_BEACON {
         return None;
     }
-    if data[1] != DISCOVERY_VERSION {
+    if data[1] != BEACON_VERSION {
         return None;
     }
     XOnlyPublicKey::from_slice(&data[2..34]).ok()
 }
 
 /// Buffer for discovered peers, drained by `discover()`.
-pub struct DiscoveryBuffer {
+pub struct NeighborBuffer {
     transport_id: TransportId,
     peers: Mutex<Vec<DiscoveredPeer>>,
 }
 
-impl DiscoveryBuffer {
-    /// Create a new empty discovery buffer.
+impl NeighborBuffer {
+    /// Create a new empty neighbor buffer.
     pub fn new(transport_id: TransportId) -> Self {
         Self {
             transport_id,
@@ -101,7 +101,7 @@ mod tests {
 
         assert_eq!(beacon.len(), BEACON_SIZE);
         assert_eq!(beacon[0], FRAME_TYPE_BEACON);
-        assert_eq!(beacon[1], DISCOVERY_VERSION);
+        assert_eq!(beacon[1], BEACON_VERSION);
 
         let parsed = parse_beacon(&beacon).unwrap();
         assert_eq!(parsed, pubkey);
@@ -134,8 +134,8 @@ mod tests {
     }
 
     #[test]
-    fn test_discovery_buffer() {
-        let buffer = DiscoveryBuffer::new(TransportId::new(1));
+    fn test_neighbor_buffer() {
+        let buffer = NeighborBuffer::new(TransportId::new(1));
         let pubkey = test_pubkey();
         let mac = [0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff];
 
@@ -152,8 +152,8 @@ mod tests {
     }
 
     #[test]
-    fn test_discovery_buffer_dedup() {
-        let buffer = DiscoveryBuffer::new(TransportId::new(1));
+    fn test_neighbor_buffer_dedup() {
+        let buffer = NeighborBuffer::new(TransportId::new(1));
         let pubkey = test_pubkey();
         let mac = [0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff];