net: CJDNS overlay (--cjdns-reachable, --only-net=cjdns)

OPERATOR.md

@@ -369,7 +369,8 @@ Clean smoke:
 | `--no-listen` / `--listen=0` | `listen=0` / `no_listen=` | bind a loopback default; **off** = no clearnet P2P socket |
 | `--listen-onion` | `listen_onion=` | **off** — loopback P2P + `ADD_ONION` (`{datadir}/onion/p2p.priv`); needs `--tor-control` and `--max-inbound` > 0 |
 | `--no-discover` | `no_discover=` | discover **on**; flag off = no home-IP self-announce; P2P/wallet onions still listed |
-| `--only-net NET` | `only_net=` | all nets; repeatable `ipv4` / `ipv6` / `onion` / `i2p` (`cjdns` later) |
+| `--only-net NET` | `only_net=` | all nets; repeatable `ipv4` / `ipv6` / `onion` / `i2p` / `cjdns` |
+| `--cjdns-reachable` | `cjdns_reachable=` | **off** — `fc00::/8` is unroutable until set; `--only-net=cjdns` requires it |
 | `--connect ADDR` | `connect=` (repeatable) | seeds; `IP:port`, Tor v3 `.onion:port`, or `{52}.b32.i2p:port` |
 | `--proxy HOST:PORT` | `proxy=` | unset — SOCKS5 for all P2P outbound |
 | `--onion HOST:PORT` | `onion=` | unset — SOCKS5 for onion destinations |
@@ -453,7 +454,7 @@ sends `tx`, and disconnects. This is **not** Dandelion++. If that
 one-shot fails, the tx stays in the mempool and is still not INV'd;
 confirmation can still arrive in a block.
 `--onion HOST:PORT` stores a separate SOCKS endpoint for onion destinations.
-`--only-net onion` (repeatable with `ipv4`/`ipv6`/`i2p`) filters dial and learn;
+`--only-net onion` (repeatable with `ipv4`/`ipv6`/`i2p`/`cjdns`) filters dial and learn;
 onion requires `--proxy` or `--onion`. `--connect foo.onion:8333` is a start
 error when the v3 checksum is invalid. The peers file is `rbitcoin-peers-v2`
 (v1 IPv4/IPv6 still loads).
@@ -488,10 +489,18 @@ error. Unset: I2P rows may still load from `peers` v2 but are not dialed.
 `--only-net i2p` without `--i2p-sam` is a start error. `--i2p-accept-incoming`
 creates a persistent local destination (`{datadir}/i2p/p2p.priv`, 0600) and
 `STREAM FORWARD`s to the P2P bind. With `--listen=0` that is a start error
-naming `--listen` (overlay incoming still needs a loopback P2P accept). NixOS:
+unless `--listen-onion` provides a loopback accept. NixOS:
 `services.rbitcoin.i2p.sam` / `i2p.acceptIncoming`; the unit `After`/`Wants`
 `i2pd.service` when SAM is set. Do not start i2pd from this module.
 
+`--cjdns-reachable` treats BIP155 `fc00::/8` as the kernel CJDNS overlay: dial
+with ordinary TCP (OS routing), advertise a `--listen` on that IPv6, keep
+tagged rows in `peers` v2. Off (default): do not dial CJDNS; do not treat
+`fc00::/8` as advertisable. `--only-net=cjdns` without the flag is a start
+error. `--listen [fc00:…]:port` binds that address when the OS has it; no
+cjdns daemon in-process and no TUN in CI. NixOS: `cjdns.reachable`;
+`After`/`Wants` `cjdns.service`. Do not start a cjdns router from this module.
+
 `--datadir` holds the node root (`store/`, `mempool/`, `peers`, `rpc.token`, `rpc.sock`).
 Omit `--datadir-cold` and cold files live there too. Set it to put the large
 rarely-read Class A **inwit** stem (`inwit.body` + `inwit.loc`, ~486 GiB + loc

crates/rbitcoin-net/src/ephemeral.rs

@@ -25,6 +25,7 @@ pub(crate) fn isolated_broadcast_targets(am: &AddrMan, max: usize) -> Vec<NetAdd
             NetAddr::Onion { .. } => onions.push(e.addr),
             NetAddr::Ip(_) => ips.push(e.addr),
             NetAddr::I2p { .. } => {}
+            NetAddr::Cjdns { .. } => {}
         }
     }
     let mut out = Vec::new();
@@ -114,7 +115,12 @@ pub fn spawn_isolated_broadcast_loop(
     }
     let mut rx = mp.subscribe_isolated();
     tokio::spawn(async move {
-        while let Ok(txid) = rx.recv().await {
+        loop {
+            let txid = match rx.recv().await {
+                Ok(txid) => txid,
+                Err(tokio::sync::broadcast::error::RecvError::Lagged(_)) => continue,
+                Err(tokio::sync::broadcast::error::RecvError::Closed) => break,
+            };
             let Some(tx) = mp.get_tx(&txid) else {
                 continue;
             };
@@ -428,6 +434,38 @@ mod tests {
         let _ = std::fs::remove_dir_all(dir);
     }
 
+    #[tokio::test]
+    async fn ephemeral_broadcast_loop_survives_lagged_kicks() {
+        use bitcoin::hashes::Hash;
+        use bitcoin::Txid;
+
+        let (dir, hub) = crate::chain::tiny_regtest_hub_labeled("iso-lag");
+        let mp = MempoolHub::open(dir.join("mp"), Arc::clone(&hub.query)).unwrap();
+        mp.set_isolated_broadcast(true);
+        let am = Arc::new(Mutex::new(AddrMan::new()));
+        let h = spawn_isolated_broadcast_loop(
+            mp.clone(),
+            Dialer::Direct,
+            am,
+            Magic::REGTEST,
+            "/rbitcoin:test/".into(),
+        );
+        tokio::time::sleep(Duration::from_millis(20)).await;
+        for i in 0..40u8 {
+            mp.mark_local_origin(Txid::from_byte_array([i; 32]));
+        }
+        tokio::time::sleep(Duration::from_millis(50)).await;
+        assert!(
+            !h.is_finished(),
+            "broadcast Lagged must not stop isolated send"
+        );
+        mp.mark_local_origin(dummy_tx().compute_txid());
+        tokio::time::sleep(Duration::from_millis(20)).await;
+        assert!(!h.is_finished());
+        h.abort();
+        let _ = std::fs::remove_dir_all(dir);
+    }
+
     #[tokio::test]
     async fn ephemeral_broadcast_known_tx_no_addrman_targets() {
         let tx = dummy_tx();

crates/rbitcoin-net/src/ibd/assign.rs

@@ -1283,6 +1283,10 @@ mod tests {
         PeerSlot {
             id,
             addr: SocketAddr::new(IpAddr::V4(Ipv4Addr::LOCALHOST), 18444 + id as u16),
+            net: crate::NetAddr::from_socket(SocketAddr::new(
+                IpAddr::V4(Ipv4Addr::LOCALHOST),
+                18444 + id as u16,
+            )),
             cmd_tx,
             in_flight: HashSet::new(),
             peer_height: 100,

crates/rbitcoin-net/src/ibd/dial.rs

@@ -336,7 +336,7 @@ pub(crate) fn apply_dial_result(book: &mut AddrMan, result: &DialBatchResult) {
         book.note_attempt_addr(addr);
     }
     for s in &result.slots {
-        book.note_connected(s.addr);
+        book.note_connected_addr(s.net);
     }
     for &(addr, kind) in &result.failed {
         book.note_connect_failed_addr(addr, kind == DialFailKind::Incompatible);
@@ -442,8 +442,7 @@ pub(crate) fn dial_blocked_addrs(
     cooldown: &HashMap<SocketAddr, Instant>,
     now: Instant,
 ) -> HashSet<crate::NetAddr> {
-    let mut blocked: HashSet<crate::NetAddr> =
-        slots.iter().map(|s| crate::NetAddr::Ip(s.addr)).collect();
+    let mut blocked: HashSet<crate::NetAddr> = slots.iter().map(|s| s.net).collect();
     for (&addr, &until) in cooldown {
         if until > now {
             blocked.insert(crate::NetAddr::Ip(addr));
@@ -454,7 +453,11 @@ pub(crate) fn dial_blocked_addrs(
 
 /// Live slot addrs whose netgroups occupy outbound diversity (cooldown is exclude-only).
 pub(crate) fn alive_dial_addrs(slots: &[PeerSlot]) -> Vec<SocketAddr> {
-    slots.iter().filter(|s| s.alive).map(|s| s.addr).collect()
+    slots
+        .iter()
+        .filter(|s| s.alive)
+        .filter_map(|s| s.net.socket_addr())
+        .collect()
 }
 
 pub(crate) fn expire_addr_cooldown(cooldown: &mut HashMap<SocketAddr, Instant>, now: Instant) {
@@ -648,6 +651,7 @@ mod tests {
         PeerSlot {
             id,
             addr: a,
+            net: crate::NetAddr::from_socket(a),
             cmd_tx,
             in_flight: HashSet::new(),
             peer_height: 0,

crates/rbitcoin-net/src/ibd/events/confirm_reject_tests.rs

@@ -1018,6 +1018,7 @@ fn confirmed_height_mids_blocked_while_densify_ahead_leaves_tip_hole() {
     let slot = PeerSlot {
         id: 0,
         addr: SocketAddr::new(IpAddr::V4(Ipv4Addr::LOCALHOST), 18444),
+        net: crate::NetAddr::from_socket(SocketAddr::new(IpAddr::V4(Ipv4Addr::LOCALHOST), 18444)),
         cmd_tx,
         in_flight: HashSet::new(),
         peer_height: 100,
@@ -1201,6 +1202,7 @@ fn zombie_pending_mid_at_confirmed_height_never_reget() {
     let slot = PeerSlot {
         id: 0,
         addr: SocketAddr::new(IpAddr::V4(Ipv4Addr::LOCALHOST), 18445),
+        net: crate::NetAddr::from_socket(SocketAddr::new(IpAddr::V4(Ipv4Addr::LOCALHOST), 18445)),
         cmd_tx,
         in_flight: HashSet::new(),
         peer_height: 100,
@@ -1800,6 +1802,7 @@ fn apply_peer_event_body_and_control_surface() {
         PeerSlot {
             id,
             addr: a,
+            net: crate::NetAddr::from_socket(a),
             cmd_tx,
             in_flight: HashSet::new(),
             peer_height: 10,
@@ -2036,6 +2039,10 @@ fn apply_peer_event_repeat_headers_skips_ensure_header_fk() {
         PeerSlot {
             id: 1,
             addr: SocketAddr::new(IpAddr::V4(Ipv4Addr::new(10, 1, 0, 1)), 18444),
+            net: crate::NetAddr::from_socket(SocketAddr::new(
+                IpAddr::V4(Ipv4Addr::new(10, 1, 0, 1)),
+                18444,
+            )),
             cmd_tx,
             in_flight: HashSet::new(),
             peer_height: 10,
@@ -2177,6 +2184,10 @@ fn apply_peer_event_block_framed_bq_horizon_and_headers_done() {
         PeerSlot {
             id,
             addr: SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 18444),
+            net: crate::NetAddr::from_socket(SocketAddr::new(
+                IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)),
+                18444,
+            )),
             cmd_tx,
             in_flight: HashSet::new(),
             peer_height: 5,
@@ -2456,6 +2467,10 @@ fn block_framed_raw_offers_body_queue_with_confirm_feed() {
         PeerSlot {
             id,
             addr: SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 18444),
+            net: crate::NetAddr::from_socket(SocketAddr::new(
+                IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)),
+                18444,
+            )),
             cmd_tx,
             in_flight: HashSet::new(),
             peer_height: 5,
@@ -2593,6 +2608,10 @@ fn known_headers_re_admit_to_ordered_after_tip_drain() {
         PeerSlot {
             id,
             addr: SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 18444),
+            net: crate::NetAddr::from_socket(SocketAddr::new(
+                IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)),
+                18444,
+            )),
             cmd_tx,
             in_flight: HashSet::new(),
             peer_height: 5,
@@ -2744,6 +2763,7 @@ fn path_slot_first_wins_chained_via_headers() {
         PeerSlot {
             id,
             addr: a,
+            net: crate::NetAddr::from_socket(a),
             cmd_tx,
             in_flight: HashSet::new(),
             peer_height: 10,

crates/rbitcoin-net/src/ibd/mod.rs

@@ -674,9 +674,7 @@
                         let mut n = 0usize;
                         for s in result.slots {
                             // Race: same addr may have connected on another path.
-                            if blocked.contains(&crate::NetAddr::Ip(s.addr))
-                                || st.slots.iter().any(|x| x.addr == s.addr)
-                            {
+                            if blocked.contains(&s.net) || st.slots.iter().any(|x| x.net == s.net) {
                                 warn!(
                                     "ibd: drop duplicate/cooldown dial peer[{}] {}",
                                     s.id, s.addr

crates/rbitcoin-net/src/ibd/peer_io.rs

@@ -89,6 +89,7 @@ impl PeerEventSinks {
 pub(crate) struct PeerSlot {
     pub id: usize,
     pub addr: SocketAddr,
+    pub net: crate::NetAddr,
     pub cmd_tx: mpsc::UnboundedSender<PeerCmd>,
     /// Hashes currently requested from this peer.
     pub in_flight: HashSet<BlockHash>,
@@ -426,6 +427,7 @@ pub(crate) async fn spawn_peer(
     Ok(PeerSlot {
         id,
         addr: version_socket,
+        net: addr,
         cmd_tx,
         in_flight: HashSet::new(),
         peer_height,
@@ -507,6 +509,10 @@ mod tests {
         PeerSlot {
             id,
             addr: SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 18444),
+            net: crate::NetAddr::from_socket(SocketAddr::new(
+                IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)),
+                18444,
+            )),
             cmd_tx,
             in_flight: HashSet::new(),
             peer_height: 100,

crates/rbitcoin-net/src/lib.rs

@@ -48,7 +48,7 @@ pub use net_permissions::{
     apply_implicit, parse_whitebind, parse_whitelist, NetPermTable, NetPermissionFlags,
     WhitebindGrant, WhitelistGrant, DEFAULT_WHITELISTFORCERELAY, DEFAULT_WHITELISTRELAY,
 };
-pub use netaddr::{addr_allowed, NetAddr, OnlyNet};
+pub use netaddr::{is_cjdns_ip, NetAddr, OnlyNet};
 pub use netgroup::netgroup;
 pub use peer::{
     drain_pending_now, flush_tx_invs, force_announce_txid, local_service_flags, run_feeler_timed,