4 files changed, 100 insertions, 16 deletions

diff --git a/src/swarm/members.rs b/src/swarm/members.rs
index cb8a558..c2edd01 100644
--- a/src/swarm/members.rs
+++ b/src/swarm/members.rs
@@ -10,8 +10,10 @@
 //!
 //! Besides its tier, an entry holds the alias a node gives itself (`--alias`), a name
 //! for people reading /peers and metrics (not unique and never an identity: the public
-//! key stays that), and an `alive` stamp the node renews now and then: the members
-//! renewed within `--electorate-window` are the electorate of a remake.
+//! key stays that), where it can be reached (`addresses`, as its transport gives them:
+//! hints for the others' transports), and an `alive` stamp the node renews now and
+//! then: the members renewed within `--electorate-window` are the electorate of a
+//! remake.
 
 use std::collections::HashMap;
 use std::time::Duration;
@@ -108,6 +110,42 @@ fn set_alias(doc: &mut AutoCommit, pk: &str, alias: Option<&str>) -> Result<(),
     }
 }
 
+fn addresses_path(pk: &str) -> Vec<String> {
+    let mut path = member_path(pk);
+    path.push("addresses".to_owned());
+    path
+}
+
+/// Addresses a member most likely has, at most: one per transport.
+const MAX_ADDRESSES: usize = 8;
+
+/// Where `pk` says it can be reached (at most `MAX_ADDRESSES`); none if its entry
+/// doesn't say.
+pub(crate) fn addresses(doc: &AutoCommit, pk: &str) -> Vec<String> {
+    match store::read_path(doc, &addresses_path(pk)) {
+        Ok(Some(JsonValue::Array(items))) => items
+            .into_iter()
+            .filter_map(|item| match item {
+                JsonValue::String(address) => Some(address),
+                _ => None,
+            })
+            .take(MAX_ADDRESSES)
+            .collect(),
+        _ => Vec::new(),
+    }
+}
+
+/// Hands every other member's addresses to the transport (`Transport::learn_addresses`):
+/// the member list is how a node finds where members it never met are.
+pub(crate) fn learn_addresses(state: &AppState, doc: &AutoCommit) {
+    let me = state.local_id();
+    for pk in members(doc) {
+        if pk != me {
+            state.transport.learn_addresses(&pk, &addresses(doc, &pk));
+        }
+    }
+}
+
 fn alive_path(pk: &str) -> Vec<String> {
     let mut path = member_path(pk);
     path.push("alive".to_owned());
@@ -146,15 +184,16 @@ fn alive_renewal(window: Duration) -> Duration {
 }
 
 /// Registers this node if it is ready and its entry is missing, keeps its alias as
-/// configured (set, changed or removed after a restart with another `--alias`), and
-/// renews its `alive` stamp now and then (see `electorate`).
+/// configured (set, changed or removed after a restart with another `--alias`) and its
+/// addresses as the transport gives them, and renews its `alive` stamp now and then
+/// (see `electorate`).
 pub(crate) async fn ensure_registered(state: &AppState) {
     if !state.is_ready().await {
         return;
     }
     let local = state.local_id().to_owned();
     let own = member_path(&local);
-    let (registered, recorded_alias, alive) = {
+    let (registered, recorded_alias, recorded_addresses, alive) = {
         let replica = state.doc.read().await;
         let registered = store::read_path(&replica.doc, &own)
             .ok()
@@ -163,14 +202,17 @@ pub(crate) async fn ensure_registered(state: &AppState) {
         (
             registered,
             alias(&replica.doc, &local),
+            addresses(&replica.doc, &local),
             millis_at(&replica.doc, &alive_path(&local)),
         )
     };
     let wanted = state.alias.clone();
+    let mut own_addresses = state.transport.local_addresses();
+    own_addresses.truncate(MAX_ADDRESSES);
     let now = state.clock.now_millis().as_u64();
 
     if !registered {
-        let mut entry = json!({ "since": now, "alive": now });
+        let mut entry = json!({ "since": now, "alive": now, "addresses": own_addresses });
         if let Some(alias) = &wanted {
             entry["alias"] = json!(alias);
         }
@@ -199,6 +241,18 @@ pub(crate) async fn ensure_registered(state: &AppState) {
         }
     }
 
+    if recorded_addresses != own_addresses {
+        let path = addresses_path(&local);
+        let value = json!(own_addresses);
+        match state
+            .mutate_doc(move |doc| store::write_path(doc, &path, &value))
+            .await
+        {
+            Ok(()) => info!(addresses = ?own_addresses, "Addresses updated in the member list"),
+            Err(error) => warn!(error = %error, "Failed to record our addresses"),
+        }
+    }
+
     if recorded_alias == wanted {
         return;
     }
diff --git a/src/swarm/peer/handshake.rs b/src/swarm/peer/handshake.rs
index 4c657ad..4a7f451 100644
--- a/src/swarm/peer/handshake.rs
+++ b/src/swarm/peer/handshake.rs
@@ -19,6 +19,9 @@ use crate::transport::{self, ParsedMessage};
 /// costs the recipient as much as it is long. A joining node needs only a few to find
 /// the swarm; the member list gives it the rest once it is ready.
 const MAX_LISTED_PEERS: usize = 64;
+/// Addresses of one peer listed in a HELLO_REPLY, at most (a node has one per transport,
+/// so a few).
+const MAX_LISTED_ADDRESSES: usize = 8;
 
 pub(crate) async fn remember_peer(state: &AppState, peer: &str) {
     if peer.is_empty() {
@@ -202,6 +205,17 @@ pub(super) async fn send_hello_reply(
         peers.sort_by_cached_key(|known| topology::pair_score(peer, known));
         peers.truncate(MAX_LISTED_PEERS);
     }
+    let peers = peers
+        .into_iter()
+        .map(|known| {
+            let mut addresses = state.transport.addresses_of(&known);
+            addresses.truncate(MAX_LISTED_ADDRESSES);
+            transport::ListedPeer {
+                id: known,
+                addresses,
+            }
+        })
+        .collect();
 
     let auth = state
         .swarm_key
@@ -237,11 +251,17 @@ pub(super) async fn send_hello_reply(
 /// Greets the peers a HELLO_REPLY listed: at most `MAX_LISTED_PEERS`, only valid
 /// identities, and, once the member list is known, only those that are our neighbours
 /// (it says whom we greet; a listed peer that isn't one would get nothing from us, so
-/// it isn't remembered either).
-pub(super) async fn discover_peers(state: &AppState, from_peer: &str, advertised_peers: &[String]) {
+/// it isn't remembered either). Where the sender reaches them is a hint to the
+/// transport (at most `MAX_LISTED_ADDRESSES` each).
+pub(super) async fn discover_peers(
+    state: &AppState,
+    from_peer: &str,
+    advertised_peers: &[transport::ListedPeer],
+) {
     let view_known = topology::view_known(state);
     let mut taken = 0;
-    for discovered_peer in advertised_peers {
+    for listed in advertised_peers {
+        let discovered_peer = &listed.id;
         if discovered_peer == from_peer || !state.transport.is_peer_id(discovered_peer) {
             continue;
         }
@@ -258,6 +278,8 @@ pub(super) async fn discover_peers(state: &AppState, from_peer: &str, advertised
         }
         taken += 1;
 
+        let addresses = &listed.addresses[..listed.addresses.len().min(MAX_LISTED_ADDRESSES)];
+        state.transport.learn_addresses(discovered_peer, addresses);
         remember_peer(state, discovered_peer).await;
         if let Err(error) = send_hello_once(state, discovered_peer).await {
             warn!(
diff --git a/src/swarm/state_file.rs b/src/swarm/state_file.rs
index 73b80a2..3693d89 100644
--- a/src/swarm/state_file.rs
+++ b/src/swarm/state_file.rs
@@ -31,7 +31,8 @@ const MIN_WRITE_INTERVAL: Duration = Duration::from_secs(3600);
 #[serde(rename_all = "camelCase")]
 pub(crate) struct Remembered {
     pub(crate) swarm_id: String,
-    /// Public keys of members to join through (sorted).
+    /// Addresses of members to join through (sorted), as their member list entries give
+    /// them (`swarm::members::addresses`).
     #[serde(default)]
     pub(crate) seeds: Vec<String>,
 }
@@ -173,16 +174,22 @@ pub(crate) async fn update(state: &AppState, now: bool) {
     }
 }
 
-/// Members to rejoin through: those alive within the electorate window, stable ones
-/// first, at most `MAX_SEEDS`, sorted. Changes only when members join, leave or change
-/// tier, so the file rarely does.
+/// Where to rejoin through: the addresses of members alive within the electorate
+/// window, stable ones first, of at most `MAX_SEEDS` members, sorted. Changes only when
+/// members join, leave, move or change tier, so the file rarely does.
 fn seeds(doc: &automerge::AutoCommit, me: &str, window: Duration, now: u64) -> Vec<String> {
     let (mut stable, transient): (Vec<String>, Vec<String>) = members::electorate(doc, now, window)
         .into_iter()
         .filter(|pk| pk != me)
         .partition(|pk| members::tier(doc, pk) == members::Tier::Stable);
     stable.extend(transient);
-    stable.truncate(MAX_SEEDS);
-    stable.sort();
-    stable
+    let mut seeds: Vec<String> = stable
+        .iter()
+        .filter(|pk| !members::addresses(doc, pk).is_empty())
+        .take(MAX_SEEDS)
+        .flat_map(|pk| members::addresses(doc, pk))
+        .collect();
+    seeds.sort();
+    seeds.dedup();
+    seeds
 }
diff --git a/src/swarm/topology.rs b/src/swarm/topology.rs
index f8a1c30..bdfeb53 100644
--- a/src/swarm/topology.rs
+++ b/src/swarm/topology.rs
@@ -134,6 +134,7 @@ pub(crate) async fn refresh(state: &AppState) -> Option<NeighbourChange> {
     }
     let (current, stable) = {
         let replica = state.doc.read().await;
+        members::learn_addresses(state, &replica.doc);
         let current = members::members(&replica.doc);
         let stable: BTreeSet<String> = current
             .iter()