libp2p: explode!

1 files changed, 0 insertions, 3411 deletions

diff --git a/src/transport/libp2p.rs b/src/transport/libp2p.rs
deleted file mode 100644
index b9f54a9..0000000
--- a/src/transport/libp2p.rs
+++ /dev/null
@@ -1,3411 +0,0 @@
-//! libp2p as a transport (`--transports libp2p`, in builds with the `libp2p` feature):
-//! direct connections over TCP (Noise, Yamux) and QUIC, to addresses this node knows.
-//!
-//! A node's transport identity is its libp2p peer ID; where it is, its listen addresses
-//! (multiaddrs ending in the peer ID, `locations`). Seeds are such multiaddrs, or ones
-//! without the peer ID, which a connection finds out. Messages go one per stream of the
-//! `/continuum/1` protocol: their length (4 bytes, big endian), then the message as
-//! `wire` encodes it. A send is done once the stream is written and closed; a connection
-//! that can't be made, or a stream that can't be written, refuses it. A stream's protocol
-//! goes with its first data, without waiting for the other side to agree
-//! (`swarm_config`): opening a stream costs no round trip.
-//!
-//! Connected peers tell each other where they listen (libp2p's identify protocol), so a
-//! node learns the addresses of peers that dialled it. A node publishes where it can be
-//! reached (`local_addresses`): the addresses it announces (`--libp2p-announce`, e.g. a
-//! public address forwarded to it), or else those it listens on, loopback left out.
-//!
-//! A node nobody can dial (behind NAT, or a closed port) can still be reached through a
-//! relay: a node of the swarm that relays (`--libp2p-relay`), or one configured
-//! (`--libp2p-relays`), on which it reserves a slot; its address through the relay
-//! (`<relay>/p2p-circuit/p2p/<it>`) is published with the others. Over a relayed connection, both sides then try to
-//! connect directly (libp2p's DCUtR, hole punching); the relay carries the traffic until
-//! that works, or for good if it doesn't (punched again now and then, `PUNCH_RETRIES`),
-//! within its limits (`RELAY_CIRCUIT_DURATION`,
-//! `RELAY_CIRCUIT_BYTES`; a circuit that ends is made again on the next send). Hole
-//! punching needs both sides to listen (`HolePunching`: at their LAN addresses too);
-//! where only one does, the other dials it directly once it knows where (`upgrade`).
-//!
-//! Of several connections to one peer (both dialled at once, or AutoNAT dialled back),
-//! all but one are closed a few seconds later (`DUPLICATE_GRACE`, `Book::duplicates`),
-//! by the side with the smaller peer ID: it keeps the direct one with the shortest round
-//! trip (libp2p's ping, on each connection), so a path over the LAN wins over one
-//! through a VPN, whichever opened first.
-//!
-//! A relay says so where it publishes its addresses: next to each, the same address
-//! ending in `/p2p-circuit` (where to reserve a slot), which other nodes find in the
-//! member list. A node that needs a relay picks up to `AUTO_RELAYS` relays
-//! (`relay_check`): those configured first, then those listed in the document
-//! (`learn_relays`), then members that relay. It needs one when
-//! it has no address others could dial, or when AutoNAT says it can't be dialled:
-//! AutoNAT asks connected peers (nodes of the swarm) to dial it back. Once AutoNAT says
-//! it can be dialled, it lets the relays it picked go.
-//!
-//! With `--libp2p-ignore`, address ranges are left out (VPNs): not published, not
-//! offered for hole punching, not dialled, and connections there refused (`Ignoring`).
-//!
-//! With `--libp2p-upnp`, a node asks its router to forward its listen ports (UPnP), and
-//! publishes the router's public address for them with its own (`Book::direct`): then
-//! it can be dialled from elsewhere, whatever the other side's NAT.
-//!
-//! With `--libp2p-mdns`, a node finds libp2p peers on its LAN (multicast DNS). Their
-//! LAN addresses are noted, and those that turn out to speak continuum (identify says
-//! so) are seeds while the node joins (`discovered_seeds`): nodes on one LAN find each
-//! other without configured seeds.
-//!
-//! It uses public libp2p infrastructure only with `--libp2p-public`: then it joins the
-//! IPFS DHT (Kademlia, through the IPFS bootstrap nodes), where it finds addresses of
-//! peers the member list doesn't have, and public peers that relay; those are picked
-//! after members that relay. Public relays keep circuits short (by default 2 minutes and
-//! 128 KiB): enough to punch holes through NATs, not to carry a swarm's traffic. Without
-//! it, relays are those configured, or members that say they relay.
-
-use std::collections::HashMap;
-use std::path::Path;
-use std::str::FromStr;
-use std::sync::{Arc, Mutex, MutexGuard};
-use std::time::Duration;
-
-use ::libp2p::multiaddr::Protocol;
-use ::libp2p::swarm::dial_opts::{DialOpts, PeerCondition};
-use ::libp2p::swarm::{ConnectionId, SwarmEvent};
-use ::libp2p::{Multiaddr, PeerId, StreamProtocol, Swarm, identity::Keypair};
-use anyhow::{Context, Result, anyhow, bail};
-use async_trait::async_trait;
-use futures::{AsyncReadExt, AsyncWriteExt, StreamExt};
-use tokio::sync::{Semaphore, mpsc, oneshot, watch};
-use tracing::{debug, info, trace, warn};
-
-use crate::locks::MutexExt;
-use crate::transport::stats::{
-    Connections, DialFailures, HolePunches, Libp2pStats, Reachability, RelaySlots, TransportStats,
-};
-use crate::transport::{
-    Addressed, Connection, EncodedMessage, HandlerFn, MessageHandler, ParsedMessage, Transport,
-    hand_on_probe, is_probe, wire,
-};
-
-/// The scheme of this transport's addresses (`transport::paths`).
-pub(crate) const SCHEME: &str = "libp2p";
-
-const PROTOCOL: StreamProtocol = StreamProtocol::new("/continuum/1");
-/// Sends taking this long are logged with where the time went (at debug).
-const SLOW_SEND: Duration = Duration::from_millis(5);
-/// The largest message read: anyone who can connect can send anything, so this bounds
-/// what one stream costs. Sync messages above 16 chunks travel as blobs.
-const MAX_MESSAGE: usize = 128 << 20;
-/// How long a connection may take to come up.
-const CONNECT_TIMEOUT: Duration = Duration::from_secs(10);
-/// A connection nobody uses is closed after this; neighbours keep theirs busy.
-const IDLE_TIMEOUT: Duration = Duration::from_secs(300);
-/// Addresses of one dial tried at once (libp2p's default: 8). Hole punching (`HolePunching`)
-/// dials every address both sides offer, where they listen (LAN, VPNs, public IPv6) and
-/// where others saw them, often more than 8, while the other side punches towards all of
-/// them at the same moment: an address dialled only after others failed (each after
-/// QUIC's 5 s handshake timeout) misses its punch, and the LAN's is often among the
-/// last. Dials of the member list's addresses (`ADDRESSES_PER_PEER`) are unchanged.
-const DIAL_CONCURRENCY: std::num::NonZeroU8 = std::num::NonZeroU8::new(32).unwrap();
-/// How long a stream may take to open and to carry a message, before what its size adds
-/// (`stream_timeout`).
-const STREAM_TIMEOUT: Duration = Duration::from_secs(10);
-/// The slowest a message is expected to go, in bytes per second.
-const MIN_RATE: u64 = 1 << 20;
-/// Inbound streams read at once.
-const READS: usize = 32;
-/// Addresses kept per peer, and peers with addresses at most.
-const ADDRESSES_PER_PEER: usize = 8;
-const MAX_PEERS: usize = 4096;
-
-/// A relayed connection (circuit) through this node lasts at most this long and carries
-/// at most this much: generous, since the swarm's own relays may carry sync traffic for
-/// good where hole punching fails (libp2p's defaults, 2 minutes and 128 KiB, are for
-/// the punching only).
-const RELAY_CIRCUIT_DURATION: Duration = Duration::from_secs(3600);
-const RELAY_CIRCUIT_BYTES: u64 = 1 << 30;
-/// Circuits through this node at once, and per peer (either end: a node behind the
-/// relay is an end of every circuit to it). libp2p's rate limits on circuits and slots
-/// (a burst, then one every minute or two, per peer and per IP address: every node
-/// behind one NAT shares one) are left out: they're for public relays serving
-/// strangers, and refused circuits used them up too.
-const RELAY_CIRCUITS: usize = 1024;
-const RELAY_CIRCUITS_PER_PEER: usize = 64;
-/// A configured relay that couldn't be reached to find out its peer ID is tried again
-/// after this.
-const RELAY_RETRY: Duration = Duration::from_secs(30);
-/// Relays picked among the members, at most, and how often a node checks whether it
-/// needs them.
-const AUTO_RELAYS: usize = 2;
-const RELAY_CHECK: Duration = Duration::from_secs(30);
-/// A relay that refused a slot (`relay_refused`: none left, not allowed, not a relay,
-/// another peer at its address: a relay restarted without its libp2p key) isn't picked
-/// again for this long. One that didn't grant it for another reason (it doesn't answer,
-/// the connection closed) isn't for `RELAY_RETRY`; a slot lost is reserved again at
-/// once.
-const RELAY_PAUSE: Duration = Duration::from_secs(600);
-/// A peer connected only through a relay is dialled directly where it can be reached
-/// (`upgrade`): first at once, then after a failure no sooner than this, doubling up to
-/// `RELAY_PAUSE`.
-const UPGRADE_RETRY: Duration = Duration::from_secs(30);
-/// A peer nobody mentioned for this long (the member list, identify, mDNS, a
-/// connection) is forgotten, unless connected: mostly old peer IDs of nodes restarted
-/// without their libp2p key, whose new ones the member list has since. Members are
-/// mentioned every few seconds (`swarm::topology`). Checked every `PRUNE_EVERY`.
-const STALE_AFTER: Duration = Duration::from_secs(600);
-const PRUNE_EVERY: Duration = Duration::from_secs(60);
-/// Several connections to one peer (both dialled at once, or AutoNAT dialled back to
-/// see whether it can) are cut to one, the fastest (`Book::duplicates`), this long after
-/// the last one opened: long enough for what it was dialled for, and for each to be
-/// pinged (at once, as it opens). Looked for every `DEDUPE_EVERY`.
-const DUPLICATE_GRACE: Duration = Duration::from_secs(10);
-/// The same while a peer is connected only through relays: a new relayed connection is
-/// a hole punch under way (`PUNCH_RETRIES`), which takes its tries (up to a QUIC
-/// handshake's 5 s each, three times) on that connection.
-const PUNCH_GRACE: Duration = Duration::from_secs(60);
-/// After libp2p's hole punching gave up on a peer (three tries, as the relayed
-/// connection opened), it tries again after these, the last one over and over: what
-/// failed may have been passing (a NAT's mapping, a busy link). Each time through a new
-/// connection through the relay, on which the peer starts the punch (`retry_punches`).
-const PUNCH_RETRIES: [Duration; 3] = [
-    Duration::from_secs(60),
-    Duration::from_secs(300),
-    Duration::from_secs(1800),
-];
-const DEDUPE_EVERY: Duration = Duration::from_secs(5);
-
-/// How long a message of `bytes` may take on a stream.
-fn stream_timeout(bytes: usize) -> Duration {
-    STREAM_TIMEOUT + Duration::from_millis(bytes as u64 * 1000 / MIN_RATE)
-}
-
-/// What a libp2p transport is made with.
-pub(crate) struct Libp2pConfig {
-    pub(crate) key: Keypair,
-    /// Multiaddrs to listen on.
-    pub(crate) listen: Vec<Multiaddr>,
-    /// Multiaddrs to publish instead of the listen addresses, if any.
-    pub(crate) announce: Vec<Multiaddr>,
-    /// Relays to reserve a slot on (multiaddrs; without the relay's peer ID, a connection
-    /// finds it out).
-    pub(crate) relays: Vec<Multiaddr>,
-    /// Relay for other nodes.
-    pub(crate) relay: bool,
-    /// Speak continuum (`PROTOCOL`): not on a node that only relays (`--relay-only`),
-    /// which nobody should take for a node.
-    pub(crate) continuum: bool,
-    /// Find peers on the LAN (mDNS).
-    pub(crate) mdns: bool,
-    /// Ask the router to forward our listen ports (UPnP), and publish where.
-    pub(crate) upnp: bool,
-    /// Address ranges neither published nor dialled, nor connected over (`Ignoring`).
-    pub(crate) ignore: Vec<IpRange>,
-    /// Use public infrastructure: the IPFS DHT, public relays.
-    pub(crate) public: bool,
-    /// libp2p's in-memory transport instead of TCP and QUIC: for tests.
-    pub(crate) memory: bool,
-}
-
-/// The multiaddrs of option `option`.
-fn parse_addresses(option: &str, addresses: &[String]) -> Result<Vec<Multiaddr>> {
-    addresses
-        .iter()
-        .map(|address| {
-            address
-                .parse::<Multiaddr>()
-                .with_context(|| format!("{option} {address:?}"))
-        })
-        .collect()
-}
-
-/// The ranges of `libp2p-ignore`.
-fn parse_ranges(ranges: &[String]) -> Result<Vec<IpRange>> {
-    ranges
-        .iter()
-        .map(|range| range.parse().context("libp2p-ignore"))
-        .collect()
-}
-
-/// This transport's options, checked when the configuration is loaded
-/// (`config::Settings::check`), so `--print-config` tells a wrong one too: the
-/// multiaddrs and ranges parse, and a relay that is no node (`--relay-only`) can be
-/// dialled and keeps its peer ID.
-pub(crate) fn check(settings: &crate::config::Settings) -> Result<()> {
-    parse_addresses("libp2p-listen", &settings.libp2p_listen)?;
-    parse_addresses("libp2p-announce", &settings.libp2p_announce)?;
-    parse_addresses("libp2p-relays", &settings.libp2p_relays)?;
-    parse_ranges(&settings.libp2p_ignore)?;
-    if settings.relay_only {
-        if settings.libp2p_listen.is_empty() {
-            bail!("relay-only needs libp2p-listen: where nodes reach the relay");
-        }
-        if settings.libp2p_key_file.is_none() {
-            bail!(
-                "relay-only needs libp2p-key-file: without it, the relay's peer ID changes with every start and nodes lose it"
-            );
-        }
-    }
-    Ok(())
-}
-
-impl Libp2pConfig {
-    /// The configuration `settings` give; `relay_only`: a relay that is no node
-    /// (`--relay-only`).
-    pub(crate) fn from_settings(
-        settings: &crate::config::Settings,
-        relay_only: bool,
-    ) -> Result<Self> {
-        let parse = parse_addresses;
-        Ok(Self {
-            key: Self::load_key(settings.libp2p_key_file.as_deref())?,
-            listen: parse("libp2p-listen", &settings.libp2p_listen)?,
-            announce: parse("libp2p-announce", &settings.libp2p_announce)?,
-            relays: parse("libp2p-relays", &settings.libp2p_relays)?,
-            relay: settings.libp2p_relay || relay_only,
-            continuum: !relay_only,
-            mdns: settings.libp2p_mdns,
-            upnp: settings.libp2p_upnp,
-            ignore: parse_ranges(&settings.libp2p_ignore)?,
-            public: settings.libp2p_public,
-            memory: false,
-        })
-    }
-
-    /// The key in `path` (32 raw bytes, an Ed25519 secret key), or a new one each start
-    /// without a file: the peer ID only says where a node is, so a new one costs nothing
-    /// but the WHO that finds it again (`transport::identity`).
-    pub(crate) fn load_key(path: Option<&Path>) -> Result<Keypair> {
-        let Some(path) = path else {
-            return Ok(Keypair::generate_ed25519());
-        };
-        let mut bytes = std::fs::read(path)
-            .with_context(|| format!("Reading the libp2p key from {}", path.display()))?;
-        crate::swarm::auth::warn_if_readable_by_others(path, "libp2p key");
-        if bytes.len() != 32 {
-            bail!(
-                "The libp2p key in {} has {} bytes; it has 32",
-                path.display(),
-                bytes.len()
-            );
-        }
-        Keypair::ed25519_from_bytes(&mut bytes)
-            .map_err(|error| anyhow!("The libp2p key in {}: {error}", path.display()))
-    }
-}
-
-enum Command {
-    /// Connect to `peer` (at `addresses`) unless connected.
-    Connect {
-        peer: PeerId,
-        addresses: Vec<Multiaddr>,
-        done: oneshot::Sender<Result<(), String>>,
-    },
-    /// Connect to `address` to find out which peer is there.
-    Identify {
-        address: Multiaddr,
-        done: oneshot::Sender<Result<PeerId, String>>,
-    },
-    /// See whether relays are needed now (one was just learned of).
-    CheckRelays,
-    /// Find out which peer relays at `address`, named without the relay's peer ID
-    /// (`Book::finding`).
-    FindRelay { address: Multiaddr },
-}
-
-/// Who named a relay to pick, in the order they are picked.
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-enum Named {
-    /// `Libp2pConfig::relays`.
-    Configured,
-    /// The relays listed in the document (`Transport::learn_relays`).
-    Listed,
-}
-
-impl Named {
-    fn as_str(self) -> &'static str {
-        match self {
-            Self::Configured => "configured",
-            Self::Listed => "listed",
-        }
-    }
-}
-
-/// A relay named to pick.
-#[derive(Clone, Debug, PartialEq, Eq)]
-struct NamedRelay {
-    /// Where, with the relay's peer ID.
-    at: Multiaddr,
-    /// As named: without the peer ID, it is found out again when the relay doesn't
-    /// grant a slot (it may have a new one).
-    given: Multiaddr,
-    named: Named,
-}
-
-/// Where peers are, and where we listen.
-#[derive(Default)]
-struct Book {
-    addresses: HashMap<PeerId, Vec<Multiaddr>>,
-    listening: Vec<Multiaddr>,
-    /// Where the router forwards to our listen addresses (UPnP, `Libp2pConfig::upnp`).
-    mapped: Vec<Multiaddr>,
-    /// `Libp2pConfig::announce`.
-    announced: Vec<Multiaddr>,
-    /// `Libp2pConfig::ignore`: not published (but announced), not dialled.
-    ignored: Vec<IpRange>,
-    /// `Libp2pConfig::relay`: this node relays, and says so.
-    serving: bool,
-    /// Relays named to pick (configured, listed), by peer: picked first.
-    named_relays: HashMap<PeerId, NamedRelay>,
-    /// Relays named without their peer ID, being found out (`Command::FindRelay`).
-    finding: HashMap<Multiaddr, Named>,
-    /// The relays listed in the document, as last learned (`learn_listed`).
-    listed: Vec<Multiaddr>,
-    /// Members that say they relay, and where (with the relay's peer ID).
-    relays: HashMap<PeerId, Multiaddr>,
-    /// With `Libp2pConfig::public`: other peers that relay (identify says so), and
-    /// where.
-    public_relays: HashMap<PeerId, Multiaddr>,
-    /// Relays not to be picked, until when (`RELAY_PAUSE`, `RELAY_RETRY`).
-    failed_relays: HashMap<PeerId, tokio::time::Instant>,
-    /// Relays that granted us a slot we hold.
-    slots: std::collections::HashSet<PeerId>,
-    /// Peers holding a slot on this node, as a relay.
-    slots_here: std::collections::HashSet<PeerId>,
-    /// Peers connected only through a relay, dialled directly (`upgrade`): when to again
-    /// at the soonest, and how long to wait after that.
-    upgrades: HashMap<PeerId, (tokio::time::Instant, Duration)>,
-    /// The shortest round trip measured on each open connection (libp2p's ping).
-    rtts: HashMap<ConnectionId, Duration>,
-    /// Peers whose hole punching failed: how often in a row, and when to try again
-    /// (`PUNCH_RETRIES`).
-    punching: HashMap<PeerId, (usize, tokio::time::Instant)>,
-    /// Open connections: to whom, whether through a relay, and the remote address.
-    connections: HashMap<ConnectionId, (PeerId, bool, Multiaddr)>,
-    /// What AutoNAT says, and the address it confirmed while public.
-    reachability: Reachability,
-    public_address: Option<Multiaddr>,
-    /// Since start (`stats`).
-    counts: Counts,
-    /// When each peer was last mentioned (`STALE_AFTER`).
-    seen: HashMap<PeerId, tokio::time::Instant>,
-    /// Peers found on the LAN (mDNS) not known yet to speak continuum.
-    lan: std::collections::HashSet<PeerId>,
-    /// Peers that speak continuum (identify says so).
-    continuum: std::collections::HashSet<PeerId>,
-    /// Peers identify says don't speak continuum, and whether they relay: not sent to
-    /// (`send_encoded`), so that a seed that's no node says so.
-    not_nodes: HashMap<PeerId, bool>,
-    /// Peers found on the LAN that speak continuum, with their address: seeds not
-    /// handed out yet (`discovered_seeds`).
-    discovered: Vec<Multiaddr>,
-}
-
-/// What `Libp2pStats` counts since start.
-#[derive(Default)]
-struct Counts {
-    slots_granted: u64,
-    slots_lost: u64,
-    slots_not_granted: u64,
-    hole_punches: HolePunches,
-    dial_failures: DialFailures,
-}
-
-/// Counts a dial that failed with `error` (not one that wasn't needed).
-/// A dial error, shortly: for each address tried (without the peer ID the caller names
-/// already), the innermost cause, once. libp2p's own text nests each transport's errors
-/// in the next ("Multiple dial errors occurred: ..."), repeating the cause at each level.
-fn describe_dial_error(error: &::libp2p::swarm::DialError) -> String {
-    use ::libp2p::swarm::DialError;
-    let DialError::Transport(errors) = error else {
-        return error.to_string();
-    };
-    let described: Vec<String> = errors
-        .iter()
-        .map(|(address, error)| {
-            let mut address = address.clone();
-            if let Some(Protocol::P2p(_)) = address.iter().last() {
-                address.pop();
-            }
-            format!("{address}: {}", innermost_causes(error))
-        })
-        .collect();
-    if described.is_empty() {
-        return error.to_string();
-    }
-    described.join("; ")
-}
-
-/// Why a slot on a relay ended, or was never granted, shortly: libp2p nests the
-/// relay's answer several types deep (`Left(Left(Left(Reservation(...))))`), and the
-/// common cases deserve a sentence.
-fn relay_failure(reason: &std::io::Result<()>) -> String {
-    let Err(error) = reason else {
-        return "closed".to_owned();
-    };
-    relay_failure_text(&format!("{error:?}"), &innermost_causes(error))
-}
-
-/// `relay_failure` on the error's debug form, and its innermost cause as text.
-fn relay_failure_text(debug: &str, innermost: &str) -> String {
-    let known = [
-        (
-            "NoAddressesInReservation",
-            "the relay gave no address to be reached through it",
-        ),
-        ("ResourceLimitExceeded", "the relay has no slot left"),
-        ("PermissionDenied", "the relay doesn't let us reserve"),
-        ("NoReservation", "the relay holds no slot for us"),
-        (
-            "connection gated",
-            "the relay refused the connection (connection gated)",
-        ),
-        (
-            "UnsupportedProtocol",
-            "the relay doesn't relay (no circuit relay protocol)",
-        ),
-        ("Timeout", "the relay didn't answer in time"),
-    ];
-    if let Some((_, said)) = known.iter().find(|(pattern, _)| debug.contains(pattern)) {
-        return (*said).to_owned();
-    }
-    // The protocol refused, but only after its first data (`swarm_config`).
-    if innermost == "Failed" {
-        return "the relay refused the circuit relay protocol (is it a relay?)".to_owned();
-    }
-    innermost.to_owned()
-}
-
-/// Whether a slot ended, or wasn't granted, because the relay refused it (its error's
-/// debug form and innermost cause, as for `relay_failure_text`), rather than because it
-/// didn't answer or the connection closed: only then is it worth not asking again for a
-/// while.
-fn relay_refused(debug: &str, innermost: &str) -> bool {
-    let refusals = [
-        "NoAddressesInReservation",
-        "ResourceLimitExceeded",
-        "PermissionDenied",
-        "connection gated",
-        "UnsupportedProtocol",
-        "WrongPeerId",
-    ];
-    refusals.iter().any(|pattern| debug.contains(pattern)) || innermost == "Failed"
-}
-
-/// The innermost of `error`'s causes, each distinct one once: those libp2p lists in a
-/// "Multiple dial errors occurred:" text (one per line, ` - <cause>: <its cause>...`),
-/// or the last of the source chain.
-fn innermost_causes(error: &(dyn std::error::Error + 'static)) -> String {
-    let mut innermost = error;
-    while let Some(source) = innermost.source() {
-        innermost = source;
-    }
-    let text = innermost.to_string();
-    let mut causes: Vec<&str> = Vec::new();
-    for line in text.lines() {
-        let Some(listed) = line.trim().strip_prefix("- ") else {
-            continue;
-        };
-        // A line ends in the next level's heading when that level lists more.
-        let cause = listed
-            .split(": ")
-            .filter(|part| !part.starts_with("Multiple dial errors"))
-            .last()
-            .unwrap_or(listed)
-            .trim();
-        if !cause.is_empty() && !causes.contains(&cause) {
-            causes.push(cause);
-        }
-    }
-    if causes.is_empty() {
-        let cause = text.rsplit(": ").next().unwrap_or(&text).trim();
-        return cause.to_owned();
-    }
-    causes.join(", ")
-}
-
-fn count_dial_failure(failures: &mut DialFailures, error: &::libp2p::swarm::DialError) {
-    use ::libp2p::swarm::DialError;
-    match error {
-        DialError::DialPeerConditionFalse(_) => {}
-        DialError::Transport(_) => failures.unreachable += 1,
-        DialError::WrongPeerId { .. } => failures.wrong_peer_id += 1,
-        DialError::NoAddresses => failures.no_addresses += 1,
-        _ => failures.other += 1,
-    }
-}
-
-impl Book {
-    /// How we are connected to `peer`: directly if any connection is direct.
-    fn connection(&self, peer: &PeerId) -> Option<Connection> {
-        book_connection(&self.connections, peer)
-    }
-
-    /// The connections to `peer` to close, of several: all but one, the oldest direct
-    /// one (the oldest relayed one if none is direct).
-    ///
-    /// None between a relay and a node with a slot on it, or reserving one (`reserving`):
-    /// a slot lives on one connection, which libp2p doesn't tell, and closing it would
-    /// end the slot, and with it every circuit to the node (the relay then answers
-    /// `NoReservation`).
-    fn duplicates(&self, peer: &PeerId, reserving: bool) -> Vec<ConnectionId> {
-        if reserving || self.slots.contains(peer) || self.slots_here.contains(peer) {
-            return Vec::new();
-        }
-        self.ranked(peer).into_iter().skip(1).collect()
-    }
-
-    /// The connections to `peer`, the one to keep first: direct ones before relayed
-    /// ones, measured ones by their round trip (`rtts`: over the LAN before a VPN's hub,
-    /// whichever opened first), then the oldest.
-    fn ranked(&self, peer: &PeerId) -> Vec<ConnectionId> {
-        let mut connections: Vec<(bool, Duration, ConnectionId)> = self
-            .connections
-            .iter()
-            .filter(|(_, (connected, _, _))| connected == peer)
-            .map(|(id, (_, relayed, _))| {
-                let rtt = self.rtts.get(id).copied().unwrap_or(Duration::MAX);
-                (*relayed, rtt, *id)
-            })
-            .collect();
-        connections.sort();
-        connections.into_iter().map(|(_, _, id)| id).collect()
-    }
-
-    /// The remote address of the connection to `peer` that is kept (`ranked`).
-    fn location(&self, peer: &PeerId) -> Option<&Multiaddr> {
-        let kept = *self.ranked(peer).first()?;
-        self.connections.get(&kept).map(|(_, _, address)| address)
-    }
-
-    fn stats(&self) -> Libp2pStats {
-        let mut connections = Connections::default();
-        for (_, relayed, _) in self.connections.values() {
-            if *relayed {
-                connections.relayed += 1;
-            } else {
-                connections.direct += 1;
-            }
-        }
-        Libp2pStats {
-            reachability: self.reachability,
-            public_address: self.public_address.as_ref().map(Multiaddr::to_string),
-            connections,
-            relay_slots: RelaySlots {
-                held: self.slots.len(),
-                paused: self
-                    .failed_relays
-                    .values()
-                    .filter(|until| tokio::time::Instant::now() < **until)
-                    .count(),
-                granted: self.counts.slots_granted,
-                lost: self.counts.slots_lost,
-                not_granted: self.counts.slots_not_granted,
-            },
-            hole_punches: self.counts.hole_punches,
-            dial_failures: self.counts.dial_failures,
-        }
-    }
-
-    /// `peer` was mentioned just now.
-    fn touch(&mut self, peer: PeerId) {
-        self.seen.insert(peer, tokio::time::Instant::now());
-    }
-
-    /// Forgets the peers not mentioned within `STALE_AFTER` before `now`, but those
-    /// `connected`. Returns how many.
-    fn prune(&mut self, now: tokio::time::Instant, connected: impl Fn(&PeerId) -> bool) -> usize {
-        let stale: Vec<PeerId> = self
-            .addresses
-            .keys()
-            .chain(self.relays.keys())
-            .chain(self.public_relays.keys())
-            .chain(self.continuum.iter())
-            .chain(self.lan.iter())
-            .filter(|peer| {
-                !connected(peer)
-                    && self
-                        .seen
-                        .get(peer)
-                        .is_none_or(|at| now.saturating_duration_since(*at) >= STALE_AFTER)
-            })
-            .copied()
-            .collect::<std::collections::HashSet<_>>()
-            .into_iter()
-            .collect();
-        for peer in &stale {
-            self.addresses.remove(peer);
-            self.relays.remove(peer);
-            self.public_relays.remove(peer);
-            self.continuum.remove(peer);
-            self.not_nodes.remove(peer);
-            self.lan.remove(peer);
-            self.failed_relays.remove(peer);
-            self.upgrades.remove(peer);
-            self.punching.remove(peer);
-            self.seen.remove(peer);
-        }
-        stale.len()
-    }
-
-    /// `peer`, found on the LAN, speaks continuum: a seed, at the address we know first.
-    fn discover(&mut self, peer: PeerId) {
-        let Some(address) = self.addresses.get(&peer).and_then(|known| known.first()) else {
-            return;
-        };
-        if let Ok(address) = address.clone().with_p2p(peer)
-            && !self.discovered.contains(&address)
-            && self.discovered.len() < MAX_PEERS
-        {
-            self.discovered.push(address);
-        }
-    }
-
-    /// Where others could dial us directly: the announced addresses, or else those we
-    /// listen on (`published`), where the router forwards to them (`mapped`), and where
-    /// AutoNAT found others can dial us (`public_address`: a port forwarded by hand, say),
-    /// without the peer ID.
-    fn direct(&self) -> Vec<Multiaddr> {
-        if !self.announced.is_empty() {
-            return self.announced.clone();
-        }
-        let direct: Vec<Multiaddr> = self
-            .listening
-            .iter()
-            .filter(|address| !is_relayed(address))
-            .cloned()
-            .collect();
-        let mut direct = published(&direct);
-        let confirmed = self.public_address.iter().filter_map(|address| {
-            let mut address = address.clone();
-            if let Some(Protocol::P2p(_)) = address.iter().last() {
-                address.pop();
-            }
-            (!address.is_empty() && !is_relayed(&address)).then_some(address)
-        });
-        // First: the member list keeps only so many (`members::MAX_ADDRESSES`), and a
-        // node listening everywhere has many.
-        let mut first: Vec<Multiaddr> = Vec::new();
-        for address in self.mapped.iter().cloned().chain(confirmed) {
-            if !first.contains(&address) {
-                first.push(address);
-            }
-        }
-        direct.retain(|address| !first.contains(address));
-        first.extend(direct);
-        first.retain(|address| !ignored(&self.ignored, address));
-        first
-    }
-}
-
-/// Whether `address` only reaches this host (or this link): no use to other hosts, and
-/// dialled by one, it reaches that host itself.
-fn is_local(address: &Multiaddr) -> bool {
-    match address.iter().next() {
-        Some(Protocol::Ip4(ip)) => ip.is_loopback() || ip.is_link_local() || ip.is_unspecified(),
-        Some(Protocol::Ip6(ip)) => {
-            ip.is_loopback() || ip.is_unicast_link_local() || ip.is_unspecified()
-        }
-        _ => false,
-    }
-}
-
-/// The addresses of `all` worth publishing: all but local ones, unless they're all
-/// local (a test on one host).
-fn published(all: &[Multiaddr]) -> Vec<Multiaddr> {
-    let reachable: Vec<Multiaddr> = all
-        .iter()
-        .filter(|address| !is_local(address))
-        .cloned()
-        .collect();
-    if reachable.is_empty() {
-        all.to_vec()
-    } else {
-        reachable
-    }
-}
-
-impl Book {
-    /// `named` names the relay at `given`; returns it if its peer is to be found out.
-    /// `local`: this node, never its own relay.
-    fn name_relay(&mut self, given: Multiaddr, named: Named, local: PeerId) -> Option<Multiaddr> {
-        match split_peer(&given) {
-            Some(peer) if peer == local => None,
-            Some(peer) => {
-                // Configured wins over listed.
-                if self
-                    .named_relays
-                    .get(&peer)
-                    .is_none_or(|known| known.named == Named::Listed || named == Named::Configured)
-                {
-                    self.named_relays.insert(
-                        peer,
-                        NamedRelay {
-                            at: given.clone(),
-                            given,
-                            named,
-                        },
-                    );
-                }
-                None
-            }
-            None => {
-                let known = self.finding.contains_key(&given)
-                    || self.named_relays.values().any(|relay| relay.given == given);
-                if known {
-                    return None;
-                }
-                self.finding.insert(given.clone(), named);
-                Some(given)
-            }
-        }
-    }
-
-    /// The relay named at `given` (without a peer ID) is `peer`: unless it is no longer
-    /// named (or is this node). Returns whether that's news.
-    fn relay_found(&mut self, given: Multiaddr, peer: PeerId, local: PeerId) -> bool {
-        let Some(named) = self.finding.remove(&given) else {
-            return false;
-        };
-        let Ok(at) = given.clone().with_p2p(peer) else {
-            return false;
-        };
-        if peer == local
-            || (named == Named::Listed
-                && self
-                    .named_relays
-                    .get(&peer)
-                    .is_some_and(|known| known.named == Named::Configured))
-        {
-            return false;
-        }
-        self.named_relays
-            .insert(peer, NamedRelay { at, given, named });
-        true
-    }
-
-    /// `relay` didn't grant a slot: if it was named without its peer ID, its address is
-    /// to be found out again, returned.
-    fn find_again(&mut self, relay: PeerId) -> Option<Multiaddr> {
-        if self
-            .named_relays
-            .get(&relay)
-            .is_none_or(|known| split_peer(&known.given).is_some())
-        {
-            return None;
-        }
-        let known = self.named_relays.remove(&relay)?;
-        self.finding.insert(known.given.clone(), known.named);
-        Some(known.given)
-    }
-
-    /// The relays listed in the document are `listed` now: returns those to find out,
-    /// None if nothing changed.
-    fn learn_listed(&mut self, listed: Vec<Multiaddr>, local: PeerId) -> Option<Vec<Multiaddr>> {
-        if listed == self.listed {
-            return None;
-        }
-        self.named_relays
-            .retain(|_, relay| relay.named != Named::Listed || listed.contains(&relay.given));
-        self.finding
-            .retain(|given, named| *named != Named::Listed || listed.contains(given));
-        self.listed = listed.clone();
-        Some(
-            listed
-                .into_iter()
-                .filter_map(|given| self.name_relay(given, Named::Listed, local))
-                .collect(),
-        )
-    }
-
-    /// The named relays `named` names, by peer, where.
-    fn named(&self, named: Named) -> HashMap<PeerId, Multiaddr> {
-        self.named_relays
-            .iter()
-            .filter(|(_, relay)| relay.named == named)
-            .map(|(peer, relay)| (*peer, relay.at.clone()))
-            .collect()
-    }
-
-    /// Where `peer` may be reached through the relays we know (named, then members that
-    /// relay): for a peer known by its ID only (a seed `/p2p/<peer ID>`), which may hold
-    /// a slot on one of them. `local`: this node, never its own relay.
-    fn through_relays(&self, peer: PeerId, local: PeerId) -> Vec<Multiaddr> {
-        let mut relays: Vec<(PeerId, Multiaddr)> = self
-            .named_relays
-            .iter()
-            .map(|(relay, named)| (*relay, named.at.clone()))
-            .collect();
-        relays.sort_by_key(|(_, address)| address.to_string());
-        let mut members: Vec<(PeerId, Multiaddr)> = self
-            .relays
-            .iter()
-            .filter(|(relay, _)| !self.named_relays.contains_key(relay))
-            .map(|(relay, address)| (*relay, address.clone()))
-            .collect();
-        members.sort_by_key(|(_, address)| address.to_string());
-        relays
-            .into_iter()
-            .chain(members)
-            .filter(|(relay, _)| *relay != local && *relay != peer)
-            .map(|(_, address)| address.with(Protocol::P2pCircuit).with(Protocol::P2p(peer)))
-            .take(ADDRESSES_PER_PEER)
-            .collect()
-    }
-
-    /// Whether all of `addresses` are known of `peer` (`remember`).
-    fn knows(&self, peer: PeerId, addresses: &[Multiaddr]) -> bool {
-        let Some(known) = self.addresses.get(&peer) else {
-            return false;
-        };
-        addresses.iter().all(|address| {
-            let mut address = address.clone();
-            if let Some(Protocol::P2p(_)) = address.iter().last() {
-                address.pop();
-            }
-            known.contains(&address)
-        })
-    }
-
-    /// `peer` is at `address` (without its `/p2p` part): kept first.
-    fn remember(&mut self, peer: PeerId, mut address: Multiaddr) {
-        if let Some(Protocol::P2p(_)) = address.iter().last() {
-            address.pop();
-        }
-        if !self.addresses.contains_key(&peer) && self.addresses.len() >= MAX_PEERS {
-            return;
-        }
-        self.touch(peer);
-        let addresses = self.addresses.entry(peer).or_default();
-        addresses.retain(|known| *known != address);
-        addresses.insert(0, address);
-        addresses.truncate(ADDRESSES_PER_PEER);
-    }
-}
-
-/// Whether `address` goes through a relay.
-fn is_relayed(address: &Multiaddr) -> bool {
-    address
-        .iter()
-        .any(|protocol| matches!(protocol, Protocol::P2pCircuit))
-}
-
-/// The relay `address` goes through, if it goes through one: the peer before
-/// `/p2p-circuit`.
-fn relay_of(address: &Multiaddr) -> Option<PeerId> {
-    let mut relay = None;
-    for protocol in address.iter() {
-        match protocol {
-            Protocol::P2p(peer) => relay = Some(peer),
-            Protocol::P2pCircuit => return relay,
-            _ => {}
-        }
-    }
-    None
-}
-
-/// The addresses of `known` this node can dial: not those through itself as the relay
-/// (a relay reaches the nodes it relays for only while they are connected to it).
-/// An address range (`10.244.0.0/16`, `42::/16`; a bare address is a range of one), for
-/// `Libp2pConfig::ignore`.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub(crate) struct IpRange {
-    network: std::net::IpAddr,
-    prefix: u8,
-}
-
-impl FromStr for IpRange {
-    type Err = anyhow::Error;
-
-    fn from_str(text: &str) -> Result<Self> {
-        let (address, prefix) = match text.split_once('/') {
-            Some((address, prefix)) => (address, Some(prefix)),
-            None => (text, None),
-        };
-        let network: std::net::IpAddr = address
-            .parse()
-            .with_context(|| format!("{text:?} is no address range (e.g. 10.244.0.0/16)"))?;
-        let bits = if network.is_ipv4() { 32 } else { 128 };
-        let prefix = match prefix {
-            Some(prefix) => prefix
-                .parse::<u8>()
-                .ok()
-                .filter(|prefix| *prefix <= bits)
-                .with_context(|| format!("{text:?}: the prefix is 0 to {bits}"))?,
-            None => bits,
-        };
-        Ok(Self { network, prefix })
-    }
-}
-
-impl IpRange {
-    fn contains(&self, ip: std::net::IpAddr) -> bool {
-        use std::net::IpAddr;
-        match (self.network, ip) {
-            (IpAddr::V4(network), IpAddr::V4(ip)) => {
-                let mask = u32::MAX
-                    .checked_shl(32 - u32::from(self.prefix))
-                    .unwrap_or(0);
-                u32::from(network) & mask == u32::from(ip) & mask
-            }
-            (IpAddr::V6(network), IpAddr::V6(ip)) => {
-                let mask = u128::MAX
-                    .checked_shl(128 - u32::from(self.prefix))
-                    .unwrap_or(0);
-                u128::from(network) & mask == u128::from(ip) & mask
-            }
-            _ => false,
-        }
-    }
-}
-
-/// Whether `address` is in one of `ranges`: a direct address there (one through a relay
-/// is judged by the connection to the relay).
-fn ignored(ranges: &[IpRange], address: &Multiaddr) -> bool {
-    if ranges.is_empty() || is_relayed(address) {
-        return false;
-    }
-    let ip = match address.iter().next() {
-        Some(Protocol::Ip4(ip)) => std::net::IpAddr::V4(ip),
-        Some(Protocol::Ip6(ip)) => std::net::IpAddr::V6(ip),
-        _ => return false,
-    };
-    ranges.iter().any(|range| range.contains(ip))
-}
-
-/// Keeps connections off the address ranges `libp2p-ignore` names, whoever dialled:
-/// hole punching and identify bring addresses there too, and a peer may dial us there.
-struct Ignoring {
-    ranges: Vec<IpRange>,
-}
-
-#[derive(Debug, thiserror::Error)]
-#[error("{0} is in a range left out (libp2p-ignore)")]
-struct IgnoredAddress(Multiaddr);
-
-impl ::libp2p::swarm::NetworkBehaviour for Ignoring {
-    type ConnectionHandler = ::libp2p::swarm::dummy::ConnectionHandler;
-    type ToSwarm = std::convert::Infallible;
-
-    fn handle_pending_inbound_connection(
-        &mut self,
-        _connection_id: ConnectionId,
-        _local_addr: &Multiaddr,
-        remote_addr: &Multiaddr,
-    ) -> Result<(), ::libp2p::swarm::ConnectionDenied> {
-        if ignored(&self.ranges, remote_addr) {
-            return Err(::libp2p::swarm::ConnectionDenied::new(IgnoredAddress(
-                remote_addr.clone(),
-            )));
-        }
-        Ok(())
-    }
-
-    fn handle_established_inbound_connection(
-        &mut self,
-        _connection_id: ConnectionId,
-        _peer: PeerId,
-        _local_addr: &Multiaddr,
-        _remote_addr: &Multiaddr,
-    ) -> Result<::libp2p::swarm::THandler<Self>, ::libp2p::swarm::ConnectionDenied> {
-        Ok(::libp2p::swarm::dummy::ConnectionHandler)
-    }
-
-    fn handle_established_outbound_connection(
-        &mut self,
-        _connection_id: ConnectionId,
-        _peer: PeerId,
-        addr: &Multiaddr,
-        _role_override: ::libp2p::core::Endpoint,
-        _port_use: ::libp2p::core::transport::PortUse,
-    ) -> Result<::libp2p::swarm::THandler<Self>, ::libp2p::swarm::ConnectionDenied> {
-        if ignored(&self.ranges, addr) {
-            return Err(::libp2p::swarm::ConnectionDenied::new(IgnoredAddress(
-                addr.clone(),
-            )));
-        }
-        Ok(::libp2p::swarm::dummy::ConnectionHandler)
-    }
-
-    fn on_swarm_event(&mut self, _event: ::libp2p::swarm::FromSwarm) {}
-
-    fn on_connection_handler_event(
-        &mut self,
-        _peer_id: PeerId,
-        _connection_id: ConnectionId,
-        event: ::libp2p::swarm::THandlerOutEvent<Self>,
-    ) {
-        match event {}
-    }
-
-    fn poll(
-        &mut self,
-        _cx: &mut std::task::Context<'_>,
-    ) -> std::task::Poll<
-        ::libp2p::swarm::ToSwarm<Self::ToSwarm, ::libp2p::swarm::THandlerInEvent<Self>>,
-    > {
-        std::task::Poll::Pending
-    }
-}
-
-/// How `peer` is connected, of `connections` (`Book::connections`): directly if one is
-/// direct.
-fn book_connection(
-    connections: &HashMap<ConnectionId, (PeerId, bool, Multiaddr)>,
-    peer: &PeerId,
-) -> Option<Connection> {
-    let mut found = None;
-    for (connected, relayed, _) in connections.values() {
-        if connected == peer {
-            if !relayed {
-                return Some(Connection::Direct);
-            }
-            found = Some(Connection::Relayed);
-        }
-    }
-    found
-}
-
-fn dialable(known: &[Multiaddr], local: PeerId) -> Vec<Multiaddr> {
-    known
-        .iter()
-        .filter(|address| relay_of(address) != Some(local))
-        .cloned()
-        .collect()
-}
-
-/// `address` with the peer ID it ends in, if it ends in one.
-fn split_peer(address: &Multiaddr) -> Option<PeerId> {
-    match address.iter().last() {
-        Some(Protocol::P2p(peer)) => Some(peer),
-        _ => None,
-    }
-}
-
-pub(crate) struct Libp2pTransport {
-    local_id: String,
-    peer_id: PeerId,
-    control: libp2p_stream::Control,
-    commands: mpsc::UnboundedSender<Command>,
-    book: Arc<Mutex<Book>>,
-    incoming: tokio::sync::Mutex<Option<libp2p_stream::IncomingStreams>>,
-    stopped: watch::Receiver<bool>,
-}
-
-fn lock(book: &Mutex<Book>) -> MutexGuard<'_, Book> {
-    book.lock_or_recover()
-}
-
-impl Libp2pTransport {
-    /// Builds the swarm, listens, and runs it in a task of its own.
-    pub(crate) fn start(config: Libp2pConfig) -> Result<Self> {
-        let peer_id = config.key.public().to_peer_id();
-        let features = Features::of(&config);
-        let mut swarm = if config.memory {
-            memory_swarm(config.key, features, config.ignore.clone())?
-        } else {
-            network_swarm(config.key, features, config.ignore.clone())?
-        };
-        for address in config.listen {
-            swarm
-                .listen_on(address.clone())
-                .with_context(|| format!("Listening on {address}"))?;
-        }
-        for address in &config.announce {
-            // Identify tells peers these.
-            swarm.add_external_address(address.clone());
-        }
-        let mut control = swarm.behaviour().stream.new_control();
-        let incoming = if config.continuum {
-            Some(
-                control
-                    .accept(PROTOCOL)
-                    .map_err(|error| anyhow!("Accepting {PROTOCOL}: {error}"))?,
-            )
-        } else {
-            None
-        };
-        let (commands, receiver) = mpsc::unbounded_channel();
-        let mut book = Book {
-            announced: config.announce,
-            ignored: config.ignore.clone(),
-            serving: config.relay,
-            ..Book::default()
-        };
-        for relay in config.relays {
-            if let Some(address) = book.name_relay(relay, Named::Configured, peer_id) {
-                let _ = commands.send(Command::FindRelay { address });
-            }
-        }
-        let book = Arc::new(Mutex::new(book));
-        let (stopping, stopped) = watch::channel(false);
-        tokio::spawn(run(
-            swarm,
-            receiver,
-            commands.clone(),
-            Arc::clone(&book),
-            Relaying {
-                serving: config.relay,
-                public: config.public,
-                local: peer_id,
-            },
-            stopping,
-        ));
-        info!(peer_id = %peer_id, "Transport started");
-        Ok(Self {
-            local_id: peer_id.to_string(),
-            peer_id,
-            control,
-            commands,
-            book,
-            incoming: tokio::sync::Mutex::new(incoming),
-            stopped,
-        })
-    }
-
-    /// Connected to `peer`, if it can be had in time.
-    async fn connect(&self, peer: PeerId) -> Result<()> {
-        let addresses = {
-            let book = lock(&self.book);
-            let mut known = book
-                .addresses
-                .get(&peer)
-                .map(|known| dialable(known, self.peer_id))
-                .unwrap_or_default();
-            known.retain(|address| !ignored(&book.ignored, address));
-            if known.is_empty() {
-                book.through_relays(peer, self.peer_id)
-            } else {
-                known
-            }
-        };
-        let (done, connected) = oneshot::channel();
-        self.commands
-            .send(Command::Connect {
-                peer,
-                addresses,
-                done,
-            })
-            .map_err(|_| anyhow!("the libp2p swarm stopped"))?;
-        match tokio::time::timeout(CONNECT_TIMEOUT, connected).await {
-            Ok(Ok(Ok(()))) => Ok(()),
-            Ok(Ok(Err(error))) => bail!("couldn't connect to {peer}: {error}"),
-            Ok(Err(_)) => bail!("the libp2p swarm stopped"),
-            Err(_) => bail!("connecting to {peer} took longer than {CONNECT_TIMEOUT:?}"),
-        }
-    }
-}
-
-/// The protocol version identify says (informational: nothing checks it).
-const IDENTIFY_VERSION: &str = "/continuum/1";
-
-#[derive(::libp2p::swarm::NetworkBehaviour)]
-struct Behaviour {
-    /// First: connections it denies need nothing from the others.
-    ignoring: Ignoring,
-    stream: libp2p_stream::Behaviour,
-    identify: ::libp2p::identify::Behaviour,
-    relay_client: ::libp2p::relay::client::Behaviour,
-    /// Only with `Libp2pConfig::relay`.
-    relay: ::libp2p::swarm::behaviour::toggle::Toggle<::libp2p::relay::Behaviour>,
-    dcutr: HolePunching,
-    /// Each connection's round trip (`Book::rtts`): of several to one peer, the fastest
-    /// is kept.
-    ping: ::libp2p::ping::Behaviour,
-    autonat: ::libp2p::autonat::Behaviour,
-    /// Only with `Libp2pConfig::mdns`.
-    mdns: ::libp2p::swarm::behaviour::toggle::Toggle<::libp2p::mdns::tokio::Behaviour>,
-    /// Only with `Libp2pConfig::upnp`: maps our listen ports on the router, and confirms
-    /// the mapped addresses as ours (identify then tells them).
-    upnp: ::libp2p::swarm::behaviour::toggle::Toggle<::libp2p::upnp::tokio::Behaviour>,
-    /// Only with `Libp2pConfig::public`: the IPFS DHT.
-    kad: ::libp2p::swarm::behaviour::toggle::Toggle<
-        ::libp2p::kad::Behaviour<::libp2p::kad::store::MemoryStore>,
-    >,
-}
-
-/// libp2p's hole punching (DCUtR), offering our listen addresses too. DCUtR offers only
-/// where others saw us (external address candidates, from identify): seen by a relay
-/// out on the internet, two nodes on one LAN are both at their router's public address,
-/// and punching through it needs the router to hairpin, which many don't. Their LAN
-/// addresses work, the firewalls on the way being stateful. Only DCUtR is told:
-/// AutoNAT would test every candidate, and fail on all of these.
-struct HolePunching {
-    inner: ::libp2p::dcutr::Behaviour,
-    /// Where we listen (`offered`).
-    listening: Vec<Multiaddr>,
-    /// `Libp2pConfig::ignore`: not offered.
-    ignored: Vec<IpRange>,
-}
-
-/// Whether DCUtR offers our listen address `address` too: neither loopback nor
-/// link-local (as for publishing), nor through a relay.
-fn offered(address: &Multiaddr) -> bool {
-    !is_local(address) && !is_relayed(address)
-}
-
-impl HolePunching {
-    fn new(local: PeerId, ignored: Vec<IpRange>) -> Self {
-        Self {
-            inner: ::libp2p::dcutr::Behaviour::new(local),
-            listening: Vec::new(),
-            ignored,
-        }
-    }
-
-    /// Tells DCUtR where we listen, as if others had seen us there. Again after every
-    /// other candidate, as DCUtR keeps the latest 20.
-    fn offer_listening(&mut self) {
-        use ::libp2p::swarm::{FromSwarm, NetworkBehaviour, NewExternalAddrCandidate};
-        for addr in &self.listening {
-            self.inner
-                .on_swarm_event(FromSwarm::NewExternalAddrCandidate(
-                    NewExternalAddrCandidate { addr },
-                ));
-        }
-    }
-}
-
-impl ::libp2p::swarm::NetworkBehaviour for HolePunching {
-    type ConnectionHandler =
-        <::libp2p::dcutr::Behaviour as ::libp2p::swarm::NetworkBehaviour>::ConnectionHandler;
-    type ToSwarm = ::libp2p::dcutr::Event;
-
-    fn handle_pending_inbound_connection(
-        &mut self,
-        connection_id: ConnectionId,
-        local_addr: &Multiaddr,
-        remote_addr: &Multiaddr,
-    ) -> Result<(), ::libp2p::swarm::ConnectionDenied> {
-        self.inner
-            .handle_pending_inbound_connection(connection_id, local_addr, remote_addr)
-    }
-
-    fn handle_established_inbound_connection(
-        &mut self,
-        connection_id: ConnectionId,
-        peer: PeerId,
-        local_addr: &Multiaddr,
-        remote_addr: &Multiaddr,
-    ) -> Result<::libp2p::swarm::THandler<Self>, ::libp2p::swarm::ConnectionDenied> {
-        if is_relayed(local_addr) {
-            // DCUtR offers its candidates on this connection: where others saw us, and
-            // these.
-            debug!(peer = %Addressed(SCHEME, &peer), listening = ?self.listening, "Reached through a relay; hole punching offers where we listen too");
-        }
-        self.inner.handle_established_inbound_connection(
-            connection_id,
-            peer,
-            local_addr,
-            remote_addr,
-        )
-    }
-
-    fn handle_pending_outbound_connection(
-        &mut self,
-        connection_id: ConnectionId,
-        maybe_peer: Option<PeerId>,
-        addresses: &[Multiaddr],
-        effective_role: ::libp2p::core::Endpoint,
-    ) -> Result<Vec<Multiaddr>, ::libp2p::swarm::ConnectionDenied> {
-        self.inner.handle_pending_outbound_connection(
-            connection_id,
-            maybe_peer,
-            addresses,
-            effective_role,
-        )
-    }
-
-    fn handle_established_outbound_connection(
-        &mut self,
-        connection_id: ConnectionId,
-        peer: PeerId,
-        addr: &Multiaddr,
-        role_override: ::libp2p::core::Endpoint,
-        port_use: ::libp2p::core::transport::PortUse,
-    ) -> Result<::libp2p::swarm::THandler<Self>, ::libp2p::swarm::ConnectionDenied> {
-        self.inner.handle_established_outbound_connection(
-            connection_id,
-            peer,
-            addr,
-            role_override,
-            port_use,
-        )
-    }
-
-    fn on_swarm_event(&mut self, event: ::libp2p::swarm::FromSwarm) {
-        use ::libp2p::swarm::FromSwarm;
-        self.inner.on_swarm_event(event);
-        match event {
-            FromSwarm::NewListenAddr(new)
-                if offered(new.addr) && !ignored(&self.ignored, new.addr) =>
-            {
-                if !self.listening.contains(new.addr) {
-                    debug!(address = %new.addr, "Offering where we listen for hole punching");
-                    self.listening.push(new.addr.clone());
-                }
-                self.offer_listening();
-            }
-            FromSwarm::ExpiredListenAddr(expired) => {
-                self.listening.retain(|address| address != expired.addr);
-            }
-            FromSwarm::NewExternalAddrCandidate(_) => self.offer_listening(),
-            _ => {}
-        }
-    }
-
-    fn on_connection_handler_event(
-        &mut self,
-        peer_id: PeerId,
-        connection_id: ConnectionId,
-        event: ::libp2p::swarm::THandlerOutEvent<Self>,
-    ) {
-        self.inner
-            .on_connection_handler_event(peer_id, connection_id, event)
-    }
-
-    fn poll(
-        &mut self,
-        cx: &mut std::task::Context<'_>,
-    ) -> std::task::Poll<
-        ::libp2p::swarm::ToSwarm<Self::ToSwarm, ::libp2p::swarm::THandlerInEvent<Self>>,
-    > {
-        self.inner.poll(cx)
-    }
-}
-
-/// What the behaviour has besides what every node has.
-#[derive(Clone, Copy)]
-struct Features {
-    relay: bool,
-    mdns: bool,
-    upnp: bool,
-    public: bool,
-}
-
-impl Features {
-    fn of(config: &Libp2pConfig) -> Self {
-        Self {
-            relay: config.relay,
-            mdns: config.mdns,
-            upnp: config.upnp,
-            public: config.public,
-        }
-    }
-}
-
-/// The IPFS DHT's protocol, and its bootstrap nodes (all at `IPFS_BOOTSTRAP_ADDRESS`).
-const IPFS_DHT: StreamProtocol = StreamProtocol::new("/ipfs/kad/1.0.0");
-const IPFS_BOOTSTRAP_ADDRESS: &str = "/dnsaddr/bootstrap.libp2p.io";
-const IPFS_BOOTSTRAP_PEERS: [&str; 4] = [
-    "QmNnooDu7bfjPFoTZYxMNLWUQJyrVwtbZg5gBMjTezGAJN",
-    "QmQCU2EcMqAqQPR2i9bChDtGNJchTbq5TbXJJ16u19uLTa",
-    "QmbLHAnMoJPWSCR5Zhtx6BHJX9KiKNN6tpvbUcqanj75Nb",
-    "QmcZf59bWwK5XFi76CZX8cbJ4BhTzzA3gU1ZjYZcYW3dwt",
-];
-/// How often a node on the DHT refreshes its routing table.
-const DHT_BOOTSTRAP: Duration = Duration::from_secs(300);
-
-impl Behaviour {
-    fn new(
-        key: &Keypair,
-        relay_client: ::libp2p::relay::client::Behaviour,
-        features: Features,
-        ignored: Vec<IpRange>,
-    ) -> std::io::Result<Self> {
-        let Features {
-            relay,
-            mdns,
-            upnp,
-            public,
-        } = features;
-        let peer_id = key.public().to_peer_id();
-        let kad = public.then(|| {
-            let mut dht = ::libp2p::kad::Behaviour::with_config(
-                peer_id,
-                ::libp2p::kad::store::MemoryStore::new(peer_id),
-                ::libp2p::kad::Config::new(IPFS_DHT),
-            );
-            let bootstrap: Multiaddr = IPFS_BOOTSTRAP_ADDRESS.parse().expect("a multiaddr");
-            for peer in IPFS_BOOTSTRAP_PEERS {
-                let peer: PeerId = peer.parse().expect("a peer ID");
-                let _ = dht.add_address(&peer, bootstrap.clone());
-            }
-            dht
-        });
-        let identify = ::libp2p::identify::Config::new(IDENTIFY_VERSION.to_owned(), key.public())
-            .with_agent_version(format!("continuum/{}", env!("CARGO_PKG_VERSION")));
-        let relay = relay.then(|| {
-            ::libp2p::relay::Behaviour::new(
-                peer_id,
-                ::libp2p::relay::Config {
-                    max_circuits: RELAY_CIRCUITS,
-                    max_circuits_per_peer: RELAY_CIRCUITS_PER_PEER,
-                    max_circuit_duration: RELAY_CIRCUIT_DURATION,
-                    max_circuit_bytes: RELAY_CIRCUIT_BYTES,
-                    reservation_rate_limiters: Vec::new(),
-                    circuit_src_rate_limiters: Vec::new(),
-                    ..Default::default()
-                },
-            )
-        });
-        let mdns = match mdns {
-            true => Some(::libp2p::mdns::tokio::Behaviour::new(
-                ::libp2p::mdns::Config::default(),
-                peer_id,
-            )?),
-            false => None,
-        };
-        Ok(Self {
-            ignoring: Ignoring {
-                ranges: ignored.clone(),
-            },
-            stream: libp2p_stream::Behaviour::new(),
-            identify: ::libp2p::identify::Behaviour::new(identify),
-            relay_client,
-            relay: relay.into(),
-            dcutr: HolePunching::new(peer_id, ignored),
-            ping: ::libp2p::ping::Behaviour::new(::libp2p::ping::Config::new()),
-            autonat: ::libp2p::autonat::Behaviour::new(
-                peer_id,
-                ::libp2p::autonat::Config {
-                    // Swarms on private networks (a LAN, WireGuard) count too.
-                    only_global_ips: false,
-                    ..Default::default()
-                },
-            ),
-            mdns: mdns.into(),
-            upnp: upnp.then(::libp2p::upnp::tokio::Behaviour::default).into(),
-            kad: kad.into(),
-        })
-    }
-}
-
-fn network_swarm(
-    key: Keypair,
-    features: Features,
-    ignored: Vec<IpRange>,
-) -> Result<Swarm<Behaviour>> {
-    Ok(::libp2p::SwarmBuilder::with_existing_identity(key)
-        .with_tokio()
-        .with_tcp(
-            ::libp2p::tcp::Config::default(),
-            ::libp2p::noise::Config::new,
-            ::libp2p::yamux::Config::default,
-        )?
-        .with_quic()
-        .with_dns()?
-        .with_relay_client(
-            ::libp2p::noise::Config::new,
-            ::libp2p::yamux::Config::default,
-        )?
-        .with_behaviour(|key, relay_client| {
-            Behaviour::new(key, relay_client, features, ignored.clone())
-                .map_err(|error| Box::new(error) as Box<dyn std::error::Error + Send + Sync>)
-        })?
-        .with_swarm_config(|config| swarm_config(config, features))
-        .build())
-}
-
-/// The swarm's settings. Streams are opened without waiting for the other side to agree
-/// on the protocol (`V1Lazy`): the protocol and the first data go together, saving a
-/// round trip per message (one stream each, module docs). That is safe only towards
-/// peers sure to speak the protocol, so not with public libp2p infrastructure
-/// (`Libp2pConfig::public`), whose nodes speak only some: there a protocol they don't
-/// would fail late, and unclearly.
-fn swarm_config(config: ::libp2p::swarm::Config, features: Features) -> ::libp2p::swarm::Config {
-    let config = config
-        .with_idle_connection_timeout(IDLE_TIMEOUT)
-        .with_dial_concurrency_factor(DIAL_CONCURRENCY);
-    if features.public {
-        config
-    } else {
-        config.with_substream_upgrade_protocol_override(::libp2p::core::upgrade::Version::V1Lazy)
-    }
-}
-
-fn memory_swarm(
-    key: Keypair,
-    features: Features,
-    ignored: Vec<IpRange>,
-) -> Result<Swarm<Behaviour>> {
-    use ::libp2p::Transport as _;
-    use ::libp2p::core::transport::{MemoryTransport, OrTransport};
-    use ::libp2p::core::upgrade::Version;
-
-    let peer_id = key.public().to_peer_id();
-    let (relay_transport, relay_client) = ::libp2p::relay::client::new(peer_id);
-    let transport = OrTransport::new(relay_transport, MemoryTransport::default())
-        .boxed()
-        .upgrade(Version::V1)
-        .authenticate(::libp2p::noise::Config::new(&key)?)
-        .multiplex(::libp2p::yamux::Config::default())
-        .timeout(CONNECT_TIMEOUT)
-        .boxed();
-    Ok(Swarm::new(
-        transport,
-        Behaviour::new(&key, relay_client, features, ignored)?,
-        peer_id,
-        swarm_config(::libp2p::swarm::Config::with_tokio_executor(), features),
-    ))
-}
-
-/// How a node relates to relays.
-struct Relaying {
-    /// It relays for others.
-    serving: bool,
-    /// Public relays may be picked, after members.
-    public: bool,
-    local: PeerId,
-}
-
-/// The relays to pick among `offers`, if this node needs relays, keeping `using`: a
-/// node needs them when it has no address others could dial (`direct`), or AutoNAT says
-/// it can't be dialled; up to `AUTO_RELAYS`, in an order of its own (the lowest hash of
-/// both peer IDs), so that not every node picks the same.
-fn relay_check(
-    local: PeerId,
-    direct: bool,
-    nat: &::libp2p::autonat::NatStatus,
-    offers: &HashMap<PeerId, Multiaddr>,
-    using: &[PeerId],
-) -> Vec<(PeerId, Multiaddr)> {
-    use ::libp2p::autonat::NatStatus;
-    let needed = match nat {
-        NatStatus::Private => true,
-        NatStatus::Public(_) => false,
-        NatStatus::Unknown => !direct,
-    };
-    if !needed || using.len() >= AUTO_RELAYS {
-        return Vec::new();
-    }
-    let score = |relay: &PeerId| {
-        use std::hash::{Hash, Hasher};
-        let mut hasher = std::collections::hash_map::DefaultHasher::new();
-        (local, relay).hash(&mut hasher);
-        hasher.finish()
-    };
-    let mut candidates: Vec<(PeerId, Multiaddr)> = offers
-        .iter()
-        .filter(|(relay, _)| **relay != local && !using.contains(relay))
-        .map(|(relay, address)| (*relay, address.clone()))
-        .collect();
-    candidates.sort_by_key(|(relay, _)| score(relay));
-    candidates.truncate(AUTO_RELAYS - using.len());
-    candidates
-}
-
-/// Reserves slots on the relays `relay_check` picks (configured ones first, then listed
-/// ones, members, public ones), and lets those picked go once AutoNAT says this node can
-/// be dialled.
-fn pick_relays(
-    swarm: &mut Swarm<Behaviour>,
-    book: &Mutex<Book>,
-    relaying: &Relaying,
-    nat: &::libp2p::autonat::NatStatus,
-    picked: &mut HashMap<::libp2p::core::transport::ListenerId, PeerId>,
-) {
-    if nat.is_public() && !picked.is_empty() {
-        info!("Reachable directly (AutoNAT); letting the relays picked go");
-        let mut book = lock(book);
-        for (listener, relay) in std::mem::take(picked) {
-            swarm.remove_listener(listener);
-            book.slots.remove(&relay);
-        }
-        return;
-    }
-    let (direct, configured, listed, members, public) = {
-        let mut book = lock(book);
-        let now = tokio::time::Instant::now();
-        book.failed_relays.retain(|_, until| now < *until);
-        let failed = book.failed_relays.clone();
-        let usable = |offers: &HashMap<PeerId, Multiaddr>| -> HashMap<PeerId, Multiaddr> {
-            offers
-                .iter()
-                .filter(|(relay, _)| !failed.contains_key(relay))
-                .map(|(relay, address)| (*relay, address.clone()))
-                .collect()
-        };
-        let public = if relaying.public {
-            usable(&book.public_relays)
-        } else {
-            HashMap::new()
-        };
-        (
-            !book.direct().is_empty(),
-            usable(&book.named(Named::Configured)),
-            usable(&book.named(Named::Listed)),
-            usable(&book.relays),
-            public,
-        )
-    };
-    let mut using: Vec<PeerId> = picked.values().copied().collect();
-    // Each kind for what the ones before left.
-    for (kind, offers) in [
-        (Named::Configured.as_str(), configured),
-        (Named::Listed.as_str(), listed),
-        ("member", members),
-        ("public", public),
-    ] {
-        for (relay, address) in relay_check(relaying.local, direct, nat, &offers, &using) {
-            using.push(relay);
-            match swarm.listen_on(address.clone().with(Protocol::P2pCircuit)) {
-                Ok(listener) => {
-                    info!(relay = %Addressed(SCHEME, &relay), address = %address, kind, "Picked a relay");
-                    picked.insert(listener, relay);
-                }
-                Err(error) => {
-                    debug!(relay = %Addressed(SCHEME, &relay), kind, error = %error, "Couldn't use a relay");
-                }
-            }
-        }
-    }
-}
-
-/// Dials `peer` directly if it's connected only through a relay and is known elsewhere
-/// too (the member list, identify, mDNS), since the first connection, made through a
-/// relay (a relayed seed), would otherwise be kept for good: a peer connected isn't
-/// dialled again, and hole punching needs both sides to listen. The direct connection,
-/// once open, wins over the relayed one (`Book::duplicates`).
-fn upgrade(swarm: &mut Swarm<Behaviour>, book: &Mutex<Book>, peer: PeerId, local: PeerId) {
-    let direct: Vec<Multiaddr> = {
-        let mut book = lock(book);
-        if book.connection(&peer) != Some(Connection::Relayed) {
-            return;
-        }
-        let direct: Vec<Multiaddr> = book
-            .addresses
-            .get(&peer)
-            .map(|known| dialable(known, local))
-            .unwrap_or_default()
-            .into_iter()
-            .filter(|address| !is_relayed(address) && !ignored(&book.ignored, address))
-            .collect();
-        if direct.is_empty() {
-            return;
-        }
-        let now = tokio::time::Instant::now();
-        let (due, wait) = book
-            .upgrades
-            .get(&peer)
-            .copied()
-            .unwrap_or((now, UPGRADE_RETRY));
-        if now < due {
-            return;
-        }
-        book.upgrades
-            .insert(peer, (now + wait, (wait * 2).min(RELAY_PAUSE)));
-        direct
-    };
-    debug!(peer = %Addressed(SCHEME, &peer), addresses = ?direct, "Connected only through a relay; dialling directly");
-    let _ = swarm.dial(
-        DialOpts::peer_id(peer)
-            .addresses(direct)
-            .condition(PeerCondition::NotDialing)
-            .build(),
-    );
-}
-
-/// Tries hole punching again with the peers it failed with that are due (`punching`).
-/// libp2p punches as a relayed connection opens, started by the side that was dialled
-/// through the relay; that side is where a punch's failure is told, so it is this one.
-/// A new relayed connection starts a new punch: we dial the peer through a relay if it
-/// has a slot on one; else we close our relayed connections to it, and its next message
-/// (a probe, within a minute) dials us through ours again. Peers connected directly by
-/// now are dropped; those not connected now are kept, failures and all.
-fn retry_punches(swarm: &mut Swarm<Behaviour>, book: &Mutex<Book>, local: PeerId) {
-    let now = tokio::time::Instant::now();
-    let mut close: Vec<ConnectionId> = Vec::new();
-    let due: Vec<(PeerId, usize, Vec<Multiaddr>)> = {
-        let mut book = lock(book);
-        let book = &mut *book;
-        let mut due = Vec::new();
-        book.punching.retain(|peer, (failed, next)| {
-            match book_connection(&book.connections, peer) {
-                Some(Connection::Direct) => return false,
-                // Kept, failures and all: one we closed to have it dial anew comes back.
-                None => return true,
-                Some(Connection::Relayed) if now < *next => return true,
-                Some(Connection::Relayed) => {}
-            }
-            let through: Vec<Multiaddr> = book
-                .addresses
-                .get(peer)
-                .map(|known| dialable(known, local))
-                .unwrap_or_default()
-                .into_iter()
-                .filter(is_relayed)
-                .collect();
-            // Until its punch fails again (or the peer tries from its side).
-            *next = now + PUNCH_RETRIES[(*failed).min(PUNCH_RETRIES.len() - 1)];
-            if through.is_empty() {
-                close.extend(
-                    book.connections
-                        .iter()
-                        .filter(|(_, (connected, relayed, _))| connected == peer && *relayed)
-                        .map(|(id, _)| *id),
-                );
-            } else {
-                due.push((*peer, *failed, through));
-            }
-            true
-        });
-        due
-    };
-    for connection in close {
-        debug!(connection = %connection, "Hole punching again: closing a relayed connection, for the peer to dial anew");
-        swarm.close_connection(connection);
-    }
-    for (peer, failed, through) in due {
-        debug!(peer = %Addressed(SCHEME, &peer), failed, "Hole punching again, through a new relayed connection");
-        let _ = swarm.dial(
-            DialOpts::peer_id(peer)
-                .addresses(through)
-                .condition(PeerCondition::Always)
-                .build(),
-        );
-    }
-}
-
-/// Asks the DHT (with `--libp2p-public`) where `peer` is, for the next attempt.
-fn find_on_dht(swarm: &mut Swarm<Behaviour>, peer: PeerId) {
-    if let Some(dht) = swarm.behaviour_mut().kad.as_mut() {
-        dht.get_closest_peers(peer);
-    }
-}
-
-/// Drives the swarm: dials what `commands` ask for and notes where we listen, until the
-/// transport is dropped. `again`: to schedule commands.
-async fn run(
-    mut swarm: Swarm<Behaviour>,
-    mut commands: mpsc::UnboundedReceiver<Command>,
-    again: mpsc::UnboundedSender<Command>,
-    book: Arc<Mutex<Book>>,
-    relaying: Relaying,
-    stopping: watch::Sender<bool>,
-) {
-    let serving = relaying.serving;
-    let mut nat = ::libp2p::autonat::NatStatus::Unknown;
-    // Relays picked, by listener.
-    let mut picked: HashMap<::libp2p::core::transport::ListenerId, PeerId> = HashMap::new();
-    let mut check = tokio::time::interval(RELAY_CHECK);
-    check.set_missed_tick_behavior(tokio::time::MissedTickBehavior::Delay);
-    let mut dht_bootstrap = tokio::time::interval(DHT_BOOTSTRAP);
-    dht_bootstrap.set_missed_tick_behavior(tokio::time::MissedTickBehavior::Delay);
-    let mut connecting: HashMap<PeerId, Vec<oneshot::Sender<Result<(), String>>>> = HashMap::new();
-    let mut identifying: HashMap<
-        ConnectionId,
-        (Multiaddr, oneshot::Sender<Result<PeerId, String>>),
-    > = HashMap::new();
-    let mut prune = tokio::time::interval(PRUNE_EVERY);
-    prune.set_missed_tick_behavior(tokio::time::MissedTickBehavior::Delay);
-    // Peers that may have several connections, and when to cut them to one. Only the
-    // side with the smaller peer ID does that, so the two never close different ones.
-    let mut dedupe_due: HashMap<PeerId, tokio::time::Instant> = HashMap::new();
-    // Connections closed as duplicates, until they are: their "Connection closed" says so.
-    let mut closing_duplicates: std::collections::HashSet<ConnectionId> =
-        std::collections::HashSet::new();
-    let mut dedupe = tokio::time::interval(DEDUPE_EVERY);
-    dedupe.set_missed_tick_behavior(tokio::time::MissedTickBehavior::Delay);
-    loop {
-        tokio::select! {
-            _ = dedupe.tick(), if !dedupe_due.is_empty() => {
-                let now = tokio::time::Instant::now();
-                let due: Vec<PeerId> = dedupe_due
-                    .iter()
-                    .filter(|(_, at)| **at <= now)
-                    .map(|(peer, _)| *peer)
-                    .collect();
-                for peer in due {
-                    dedupe_due.remove(&peer);
-                    let reserving = picked.values().any(|relay| *relay == peer);
-                    let duplicates = lock(&book).duplicates(&peer, reserving);
-                    for connection in duplicates {
-                        if swarm.close_connection(connection) {
-                            closing_duplicates.insert(connection);
-                        }
-                    }
-                }
-            }
-            _ = prune.tick() => {
-                let forgotten = lock(&book).prune(tokio::time::Instant::now(), |peer| swarm.is_connected(peer));
-                if forgotten > 0 {
-                    debug!(forgotten, "Forgot peers nobody mentions any more");
-                }
-            }
-            _ = dht_bootstrap.tick(), if relaying.public => {
-                if let Some(dht) = swarm.behaviour_mut().kad.as_mut()
-                    && let Err(error) = dht.bootstrap()
-                {
-                    warn!(error = %error, "Couldn't join the IPFS DHT");
-                }
-            }
-            _ = check.tick() => {
-                pick_relays(&mut swarm, &book, &relaying, &nat, &mut picked);
-                retry_punches(&mut swarm, &book, relaying.local);
-            }
-            command = commands.recv() => match command {
-                None => break,
-                Some(Command::CheckRelays) => {
-                    pick_relays(&mut swarm, &book, &relaying, &nat, &mut picked);
-                }
-                Some(Command::Connect { peer, addresses, done }) => {
-                    if swarm.is_connected(&peer) {
-                        let _ = done.send(Ok(()));
-                        upgrade(&mut swarm, &book, peer, relaying.local);
-                        continue;
-                    }
-                    let waiting = connecting.entry(peer).or_default();
-                    waiting.push(done);
-                    if waiting.len() > 1 {
-                        continue; // Already dialing.
-                    }
-                    let mut opts = DialOpts::peer_id(peer)
-                        .addresses(addresses)
-                        .condition(PeerCondition::DisconnectedAndNotDialing);
-                    if relaying.public {
-                        // Addresses the DHT knows too.
-                        opts = opts.extend_addresses_through_behaviour();
-                    }
-                    if let Err(error) = swarm.dial(opts.build()) {
-                        count_dial_failure(&mut lock(&book).counts.dial_failures, &error);
-                        for done in connecting.remove(&peer).into_iter().flatten() {
-                            let _ = done.send(Err(error.to_string()));
-                        }
-                        find_on_dht(&mut swarm, peer);
-                    }
-                }
-                Some(Command::FindRelay { address }) => {
-                    let again = again.clone();
-                    let local = relaying.local;
-                    let book = Arc::clone(&book);
-                    tokio::spawn(async move {
-                        let (done, identified) = oneshot::channel();
-                        if again
-                            .send(Command::Identify { address: address.clone(), done })
-                            .is_err()
-                        {
-                            return;
-                        }
-                        match tokio::time::timeout(CONNECT_TIMEOUT, identified).await {
-                            Ok(Ok(Ok(peer))) => {
-                                if lock(&book).relay_found(address.clone(), peer, local) {
-                                    debug!(relay = %Addressed(SCHEME, &address), peer = %Addressed(SCHEME, &peer), "Found a named relay");
-                                    let _ = again.send(Command::CheckRelays);
-                                }
-                            }
-                            failed => {
-                                if !lock(&book).finding.contains_key(&address) {
-                                    return; // No longer named.
-                                }
-                                let error = match failed {
-                                    Ok(Ok(Err(error))) => error,
-                                    Ok(_) => "the libp2p swarm stopped".to_owned(),
-                                    Err(_) => format!("no answer within {CONNECT_TIMEOUT:?}"),
-                                };
-                                warn!(relay = %Addressed(SCHEME, &address), error = %error, retry = ?RELAY_RETRY, "Couldn't reach a named relay; trying again later");
-                                tokio::time::sleep(RELAY_RETRY).await;
-                                let _ = again.send(Command::FindRelay { address });
-                            }
-                        }
-                    });
-                }
-                Some(Command::Identify { address, done }) => {
-                    let opts = DialOpts::unknown_peer_id().address(address.clone()).build();
-                    let id = opts.connection_id();
-                    match swarm.dial(opts) {
-                        Ok(()) => {
-                            identifying.insert(id, (address, done));
-                        }
-                        Err(error) => {
-                            let _ = done.send(Err(error.to_string()));
-                        }
-                    }
-                }
-            },
-            event = swarm.select_next_some() => match event {
-                SwarmEvent::ConnectionEstablished { peer_id, connection_id, endpoint, .. } => {
-                    {
-                        let mut book = lock(&book);
-                        book.touch(peer_id);
-                        let relayed = endpoint.is_relayed();
-                        book.connections.insert(
-                            connection_id,
-                            (peer_id, relayed, endpoint.get_remote_address().clone()),
-                        );
-                        if !relayed {
-                            book.upgrades.remove(&peer_id);
-                            book.punching.remove(&peer_id);
-                        }
-                        if relaying.local < peer_id
-                            && book.connections.values().filter(|(connected, _, _)| *connected == peer_id).count() > 1
-                        {
-                            // Only through relays: maybe a punch under way.
-                            let grace = match book.connection(&peer_id) {
-                                Some(Connection::Relayed) => PUNCH_GRACE,
-                                _ => DUPLICATE_GRACE,
-                            };
-                            dedupe_due.insert(peer_id, tokio::time::Instant::now() + grace);
-                        }
-                        debug!(
-                            peer = %Addressed(SCHEME, &peer_id),
-                            connection = %connection_id,
-                            dialled = endpoint.is_dialer(),
-                            address = %endpoint.get_remote_address(),
-                            relayed,
-                            "Connection opened"
-                        );
-                    }
-                    for done in connecting.remove(&peer_id).into_iter().flatten() {
-                        let _ = done.send(Ok(()));
-                    }
-                    if let Some((address, done)) = identifying.remove(&connection_id) {
-                        lock(&book).remember(peer_id, address);
-                        let _ = done.send(Ok(peer_id));
-                    }
-                }
-                SwarmEvent::ConnectionClosed { peer_id, connection_id, cause, .. } => {
-                    {
-                        let mut book = lock(&book);
-                        book.connections.remove(&connection_id);
-                        book.rtts.remove(&connection_id);
-                    }
-                    let cause = match cause {
-                        _ if closing_duplicates.remove(&connection_id) => "a duplicate".to_owned(),
-                        // By us, or idle: libp2p doesn't tell which.
-                        None => "closed here".to_owned(),
-                        Some(error) => error.to_string(),
-                    };
-                    debug!(
-                        peer = %Addressed(SCHEME, &peer_id),
-                        connection = %connection_id,
-                        cause = ?cause,
-                        "Connection closed"
-                    );
-                }
-                SwarmEvent::OutgoingConnectionError { connection_id, peer_id, error } => {
-                    count_dial_failure(&mut lock(&book).counts.dial_failures, &error);
-                    if let Some((_, done)) = identifying.remove(&connection_id) {
-                        let _ = done.send(Err(describe_dial_error(&error)));
-                    }
-                    if let Some(peer) = peer_id
-                        && !swarm.is_connected(&peer)
-                        && let Some(waiting) = connecting.remove(&peer)
-                    {
-                        for done in waiting {
-                            let _ = done.send(Err(describe_dial_error(&error)));
-                        }
-                        find_on_dht(&mut swarm, peer);
-                    }
-                }
-                SwarmEvent::NewListenAddr { address, .. } => {
-                    info!(address = %address, "Listening");
-                    // A relay tells those reserving where it is: its external addresses.
-                    if serving && !is_local(&address) && !is_relayed(&address) {
-                        swarm.add_external_address(address.clone());
-                    }
-                    let mut book = lock(&book);
-                    if !book.listening.contains(&address) {
-                        book.listening.push(address);
-                    }
-                }
-                SwarmEvent::ExpiredListenAddr { address, .. } => {
-                    info!(address = %address, "No longer listening");
-                    if serving {
-                        swarm.remove_external_address(&address);
-                    }
-                    lock(&book).listening.retain(|known| *known != address);
-                }
-                SwarmEvent::ListenerClosed { listener_id, addresses, reason } => {
-                    lock(&book)
-                        .listening
-                        .retain(|known| !addresses.contains(known));
-                    // A relay picked: the next check picks again, another one if this one
-                    // never granted the slot.
-                    if let Some(relay) = picked.remove(&listener_id) {
-                        let refused = match &reason {
-                            Ok(()) => false,
-                            Err(error) => relay_refused(&format!("{error:?}"), &innermost_causes(error)),
-                        };
-                        let (lost, pause) = {
-                            let mut book = lock(&book);
-                            let lost = book.slots.remove(&relay);
-                            let pause = match (refused, lost) {
-                                (true, _) => Some(RELAY_PAUSE),
-                                (false, true) => None,
-                                (false, false) => Some(RELAY_RETRY),
-                            };
-                            if lost {
-                                book.counts.slots_lost += 1;
-                            } else {
-                                book.counts.slots_not_granted += 1;
-                                // Named without its peer ID: maybe another one now.
-                                if let Some(address) = book.find_again(relay) {
-                                    let _ = again.send(Command::FindRelay { address });
-                                }
-                            }
-                            if let Some(pause) = pause {
-                                book.failed_relays.insert(relay, tokio::time::Instant::now() + pause);
-                            }
-                            (lost, pause)
-                        };
-                        // Again at once, or others meanwhile.
-                        let _ = again.send(Command::CheckRelays);
-                        let reason = relay_failure(&reason);
-                        match (lost, pause) {
-                            (true, None) => {
-                                info!(relay = %Addressed(SCHEME, &relay), reason = %reason, "Lost the slot on a relay; reserving again");
-                            }
-                            (true, Some(pause)) => {
-                                info!(relay = %Addressed(SCHEME, &relay), pause = ?pause, reason = %reason, "Lost the slot on a relay; picking others for a while");
-                            }
-                            (false, pause) => {
-                                info!(
-                                    relay = %Addressed(SCHEME, &relay),
-                                    pause = ?pause.unwrap_or_default(),
-                                    reason = %reason,
-                                    "A relay didn't grant a slot; picking others for a while"
-                                );
-                            }
-                        }
-                    }
-                }
-                SwarmEvent::ListenerError { error, .. } => {
-                    warn!(error = %error, "Listener failed");
-                }
-                SwarmEvent::Behaviour(BehaviourEvent::RelayClient(
-                    ::libp2p::relay::client::Event::ReservationReqAccepted { relay_peer_id, renewal, .. },
-                )) => {
-                    {
-                        let mut book = lock(&book);
-                        book.slots.insert(relay_peer_id);
-                        book.failed_relays.remove(&relay_peer_id);
-                        if !renewal {
-                            book.counts.slots_granted += 1;
-                        }
-                    }
-                    if !renewal {
-                        info!(relay = %Addressed(SCHEME, &relay_peer_id), "Reachable through a relay");
-                    }
-                }
-                SwarmEvent::Behaviour(BehaviourEvent::Autonat(
-                    ::libp2p::autonat::Event::StatusChanged { old, new },
-                )) => {
-                    info!(old = ?old, new = ?new, "Reachability (AutoNAT)");
-                    {
-                        use ::libp2p::autonat::NatStatus;
-                        let mut book = lock(&book);
-                        (book.reachability, book.public_address) = match &new {
-                            NatStatus::Unknown => (Reachability::Unknown, None),
-                            NatStatus::Private => (Reachability::Private, None),
-                            NatStatus::Public(address) => {
-                                (Reachability::Public, Some(address.clone()))
-                            }
-                        };
-                    }
-                    nat = new;
-                }
-                SwarmEvent::Behaviour(BehaviourEvent::Relay(event)) => {
-                    {
-                        use ::libp2p::relay::Event;
-                        let mut book = lock(&book);
-                        match &event {
-                            Event::ReservationReqAccepted { src_peer_id, .. } => {
-                                book.slots_here.insert(*src_peer_id);
-                            }
-                            Event::ReservationClosed { src_peer_id }
-                            | Event::ReservationTimedOut { src_peer_id } => {
-                                book.slots_here.remove(src_peer_id);
-                            }
-                            _ => {}
-                        }
-                    }
-                    debug!(event = ?event, "Relay event");
-                }
-                SwarmEvent::Behaviour(BehaviourEvent::Ping(::libp2p::ping::Event {
-                    peer,
-                    connection,
-                    result,
-                })) => match result {
-                    Ok(rtt) => {
-                        let mut book = lock(&book);
-                        if book.connections.contains_key(&connection) {
-                            let shortest = book.rtts.entry(connection).or_insert(rtt);
-                            *shortest = (*shortest).min(rtt);
-                        }
-                        trace!(peer = %Addressed(SCHEME, &peer), connection = %connection, rtt = ?rtt, "Connection's round trip");
-                    }
-                    Err(error) => {
-                        trace!(peer = %Addressed(SCHEME, &peer), connection = %connection, error = %error, "Connection's ping failed");
-                    }
-                },
-                SwarmEvent::Behaviour(BehaviourEvent::Upnp(event)) => match event {
-                    ::libp2p::upnp::Event::NewExternalAddr {
-                        local_addr,
-                        external_addr: address,
-                    } => {
-                        info!(address = %address, to = %local_addr, "The router forwards to us (UPnP)");
-                        let mut book = lock(&book);
-                        if !book.mapped.contains(&address) {
-                            book.mapped.push(address);
-                        }
-                    }
-                    ::libp2p::upnp::Event::ExpiredExternalAddr {
-                        local_addr,
-                        external_addr: address,
-                    } => {
-                        info!(address = %address, to = %local_addr, "The router no longer forwards to us (UPnP)");
-                        lock(&book).mapped.retain(|mapped| *mapped != address);
-                    }
-                    ::libp2p::upnp::Event::GatewayNotFound => {
-                        info!("No router that maps ports (UPnP) answered");
-                    }
-                    ::libp2p::upnp::Event::NonRoutableGateway => {
-                        warn!("The router that maps ports (UPnP) is behind another NAT itself; its mappings don't reach us from outside");
-                    }
-                },
-                SwarmEvent::Behaviour(BehaviourEvent::Dcutr(event)) => match event.result {
-                    Ok(_) => {
-                        let mut book = lock(&book);
-                        book.counts.hole_punches.succeeded += 1;
-                        book.punching.remove(&event.remote_peer_id);
-                        drop(book);
-                        info!(peer = %Addressed(SCHEME, &event.remote_peer_id), "Connected directly to a peer behind a relay");
-                    }
-                    Err(error) => {
-                        let retry = {
-                            let mut book = lock(&book);
-                            book.counts.hole_punches.failed += 1;
-                            let failed = book
-                                .punching
-                                .get(&event.remote_peer_id)
-                                .map_or(0, |(failed, _)| *failed);
-                            let retry = PUNCH_RETRIES[failed.min(PUNCH_RETRIES.len() - 1)];
-                            book.punching.insert(
-                                event.remote_peer_id,
-                                (failed + 1, tokio::time::Instant::now() + retry),
-                            );
-                            retry
-                        };
-                        debug!(peer = %Addressed(SCHEME, &event.remote_peer_id), error = %error, retry = ?retry, "Couldn't connect directly to a peer behind a relay; the relay carries on");
-                    }
-                },
-                SwarmEvent::Behaviour(BehaviourEvent::Identify(
-                    ::libp2p::identify::Event::Received { connection_id, peer_id, info },
-                )) => {
-                    {
-                        let mut book = lock(&book);
-                        let listen = published(&info.listen_addrs);
-                        // Every new connection identifies again: logged when it says something new.
-                        if book.knows(peer_id, &listen) {
-                            trace!(peer = %Addressed(SCHEME, &peer_id), connection = %connection_id, "Peer identified again");
-                        } else {
-                            debug!(
-                                peer = %Addressed(SCHEME, &peer_id),
-                                connection = %connection_id,
-                                listen = ?info.listen_addrs,
-                                observed = %info.observed_addr,
-                                agent = %info.agent_version,
-                                "Peer identified"
-                            );
-                        }
-                        // Last first: `remember` puts each in front.
-                        for address in listen.into_iter().rev() {
-                            book.remember(peer_id, address);
-                        }
-                        if relaying.public
-                            && info.protocols.contains(&::libp2p::relay::HOP_PROTOCOL_NAME)
-                            && (book.public_relays.len() < MAX_PEERS
-                                || book.public_relays.contains_key(&peer_id))
-                            && let Some(address) = book
-                                .addresses
-                                .get(&peer_id)
-                                .and_then(|known| known.first())
-                                .and_then(|address| address.clone().with_p2p(peer_id).ok())
-                        {
-                            book.public_relays.insert(peer_id, address);
-                        }
-                        if !info.protocols.contains(&PROTOCOL)
-                            && (book.not_nodes.len() < MAX_PEERS
-                                || book.not_nodes.contains_key(&peer_id))
-                        {
-                            let relays = info.protocols.contains(&::libp2p::relay::HOP_PROTOCOL_NAME);
-                            book.not_nodes.insert(peer_id, relays);
-                        }
-                        if info.protocols.contains(&PROTOCOL) {
-                            book.not_nodes.remove(&peer_id);
-                            book.continuum.insert(peer_id);
-                            if book.lan.remove(&peer_id) {
-                                book.discover(peer_id);
-                            }
-                        }
-                    }
-                    upgrade(&mut swarm, &book, peer_id, relaying.local);
-                }
-                SwarmEvent::Behaviour(BehaviourEvent::Mdns(
-                    ::libp2p::mdns::Event::Discovered(found),
-                )) => {
-                    for (peer, address) in found {
-                        if peer == relaying.local {
-                            continue;
-                        }
-                        debug!(peer = %Addressed(SCHEME, &peer), address = %address, "Peer on the LAN");
-                        let continuum = {
-                            let mut book = lock(&book);
-                            book.remember(peer, address.clone());
-                            book.continuum.contains(&peer)
-                        };
-                        upgrade(&mut swarm, &book, peer, relaying.local);
-                        if continuum {
-                            lock(&book).discover(peer);
-                        } else if lock(&book).lan.len() < MAX_PEERS {
-                            // Connected, identify says whether it speaks continuum.
-                            lock(&book).lan.insert(peer);
-                            let _ = swarm.dial(
-                                DialOpts::peer_id(peer)
-                                    .addresses(vec![address])
-                                    .condition(PeerCondition::DisconnectedAndNotDialing)
-                                    .build(),
-                            );
-                        }
-                    }
-                }
-                _ => {}
-            },
-        }
-    }
-    let _ = stopping.send(true);
-}
-
-/// One message from an inbound stream.
-async fn read_message(mut stream: ::libp2p::Stream) -> Result<Vec<u8>> {
-    let mut length = [0u8; 4];
-    tokio::time::timeout(STREAM_TIMEOUT, stream.read_exact(&mut length))
-        .await
-        .map_err(|_| anyhow!("no length within {STREAM_TIMEOUT:?}"))??;
-    let length = u32::from_be_bytes(length) as usize;
-    if length > MAX_MESSAGE {
-        bail!("a message of {length} bytes; at most {MAX_MESSAGE} are read");
-    }
-    let mut body = vec![0u8; length];
-    tokio::time::timeout(stream_timeout(length), stream.read_exact(&mut body))
-        .await
-        .map_err(|_| {
-            anyhow!(
-                "{length} bytes took longer than {:?}",
-                stream_timeout(length)
-            )
-        })??;
-    Ok(body)
-}
-
-#[async_trait]
-impl Transport for Libp2pTransport {
-    fn local_id(&self) -> &str {
-        &self.local_id
-    }
-
-    fn is_peer_id(&self, id: &str) -> bool {
-        PeerId::from_str(id).is_ok()
-    }
-
-    /// The longest a message may take on a stream.
-    fn delivery_limit(&self) -> Duration {
-        stream_timeout(MAX_MESSAGE)
-    }
-
-    /// Where we can be reached, each with our peer ID: the announced addresses, or else
-    /// those we listen on (`published`), and those through relays. A relay adds each
-    /// direct one again, ending in `/p2p-circuit`: where to reserve a slot.
-    fn local_addresses(&self) -> Vec<String> {
-        let book = lock(&self.book);
-        let direct: Vec<Multiaddr> = book
-            .direct()
-            .into_iter()
-            .filter_map(|address| address.with_p2p(self.peer_id).ok())
-            .collect();
-        let relayed = book
-            .listening
-            .iter()
-            .filter(|address| is_relayed(address))
-            .filter_map(|address| address.clone().with_p2p(self.peer_id).ok());
-        let offers: Vec<Multiaddr> = if book.serving {
-            direct
-                .iter()
-                .map(|address| address.clone().with(Protocol::P2pCircuit))
-                .collect()
-        } else {
-            Vec::new()
-        };
-        direct
-            .into_iter()
-            .chain(relayed)
-            .chain(offers)
-            .map(|address| address.to_string())
-            .collect()
-    }
-
-    /// A peer ID, or a multiaddr ending in one (noted as where that peer is).
-    fn locate(&self, target: &str) -> Option<String> {
-        if let Ok(peer) = PeerId::from_str(target) {
-            return Some(peer.to_string());
-        }
-        let mut address = Multiaddr::from_str(target).ok()?;
-        // A relay saying where to reserve a slot: `<address>/p2p/<relay>/p2p-circuit`.
-        if let Some(Protocol::P2pCircuit) = address.iter().last() {
-            address.pop();
-            let relay = split_peer(&address)?;
-            if relay != self.peer_id {
-                let new = {
-                    let mut book = lock(&self.book);
-                    let new = book.relays.get(&relay) != Some(&address);
-                    if new && (book.relays.len() < MAX_PEERS || book.relays.contains_key(&relay)) {
-                        book.relays.insert(relay, address.clone());
-                    }
-                    book.remember(relay, address);
-                    new
-                };
-                if new {
-                    let _ = self.commands.send(Command::CheckRelays);
-                }
-            }
-            return Some(relay.to_string());
-        }
-        let peer = split_peer(&address)?;
-        address.pop();
-        // A peer ID only says nothing about where.
-        if peer != self.peer_id && !address.is_empty() {
-            lock(&self.book).remember(peer, address);
-        }
-        Some(peer.to_string())
-    }
-
-    /// Multiaddrs, with or without the relay's peer ID; others are ignored.
-    fn learn_relays(&self, targets: &[String]) {
-        let listed = targets
-            .iter()
-            .filter_map(|target| Multiaddr::from_str(target).ok())
-            .collect();
-        let Some(found) = lock(&self.book).learn_listed(listed, self.peer_id) else {
-            return;
-        };
-        for address in found {
-            let _ = self.commands.send(Command::FindRelay { address });
-        }
-        let _ = self.commands.send(Command::CheckRelays);
-    }
-
-    fn connection(&self, target: &str) -> Option<Connection> {
-        let peer = PeerId::from_str(target).ok()?;
-        lock(&self.book).connection(&peer)
-    }
-
-    fn punching(&self, target: &str) -> Option<crate::transport::Punching> {
-        let peer = PeerId::from_str(target).ok()?;
-        let (failed, next) = *lock(&self.book).punching.get(&peer)?;
-        Some(crate::transport::Punching {
-            failed,
-            next_in_secs: next
-                .saturating_duration_since(tokio::time::Instant::now())
-                .as_secs(),
-        })
-    }
-
-    fn location(&self, target: &str) -> Option<String> {
-        let peer = PeerId::from_str(target).ok()?;
-        let address = lock(&self.book).location(&peer)?.clone();
-        Some(
-            address
-                .with_p2p(peer)
-                .unwrap_or_else(|address| address)
-                .to_string(),
-        )
-    }
-
-    fn stats(&self) -> TransportStats {
-        TransportStats {
-            libp2p: Some(lock(&self.book).stats()),
-            ..TransportStats::default()
-        }
-    }
-
-    /// Nodes found on the LAN (mDNS) that speak continuum.
-    fn discovered_seeds(&self) -> Vec<String> {
-        std::mem::take(&mut lock(&self.book).discovered)
-            .iter()
-            .map(Multiaddr::to_string)
-            .collect()
-    }
-
-    /// Where `target` is, each address with its peer ID.
-    fn locations(&self, target: &str) -> Vec<String> {
-        let Ok(peer) = PeerId::from_str(target) else {
-            return Vec::new();
-        };
-        lock(&self.book)
-            .addresses
-            .get(&peer)
-            .into_iter()
-            .flatten()
-            .filter_map(|address| address.clone().with_p2p(peer).ok())
-            .map(|address| address.to_string())
-            .collect()
-    }
-
-    /// A multiaddr ending in a peer ID is that peer; one without is connected to, to
-    /// find out. A bare peer ID resolves if this transport knows where it is.
-    async fn resolve_seed(&self, seed: &str) -> Result<String> {
-        let address = match PeerId::from_str(seed) {
-            Ok(peer) => Multiaddr::empty().with(Protocol::P2p(peer)),
-            Err(_) => {
-                Multiaddr::from_str(seed).with_context(|| format!("{seed} is no multiaddr"))?
-            }
-        };
-        // A peer ID only (`/p2p/<peer ID>`): reached where it's known, or through the
-        // relays we know.
-        if let [Protocol::P2p(peer)] = address.iter().collect::<Vec<_>>()[..] {
-            let book = lock(&self.book);
-            if book.addresses.contains_key(&peer)
-                || !book.through_relays(peer, self.peer_id).is_empty()
-            {
-                return Ok(peer.to_string());
-            }
-            bail!(
-                "no address known for libp2p peer {peer}, and no relay to reach it through; \
-                 give a multiaddr, or a relay (libp2p-relays)"
-            );
-        }
-        if let Some(peer) = self.locate(seed) {
-            return Ok(peer);
-        }
-        let (done, identified) = oneshot::channel();
-        self.commands
-            .send(Command::Identify { address, done })
-            .map_err(|_| anyhow!("the libp2p swarm stopped"))?;
-        match tokio::time::timeout(CONNECT_TIMEOUT, identified).await {
-            Ok(Ok(Ok(peer))) => Ok(peer.to_string()),
-            Ok(Ok(Err(error))) => bail!("couldn't connect to {seed}: {error}"),
-            Ok(Err(_)) => bail!("the libp2p swarm stopped"),
-            Err(_) => bail!("connecting to {seed} took longer than {CONNECT_TIMEOUT:?}"),
-        }
-    }
-
-    fn encode(&self, peer: &str, message: &ParsedMessage) -> Result<EncodedMessage> {
-        let body = wire::encode(message)?;
-        Ok(EncodedMessage {
-            peer: peer.to_owned(),
-            address: peer.to_owned(),
-            payload_len: body.len(),
-            body: body.into(),
-            kind: message.kind(),
-            message: None,
-        })
-    }
-
-    async fn send_encoded(&self, message: &EncodedMessage) -> Result<()> {
-        let peer = PeerId::from_str(&message.peer)
-            .with_context(|| format!("{} is no libp2p peer ID", message.peer))?;
-        let started = std::time::Instant::now();
-        self.connect(peer).await?;
-        // The protocol goes with the first data (`swarm_config`), so a peer that doesn't
-        // speak it seems to take the message: once identify has told, say so.
-        if let Some(relays) = lock(&self.book).not_nodes.get(&peer).copied() {
-            if relays {
-                bail!(
-                    "{peer} is a relay, not a node: give a node behind it as the seed \
-                     (<relay>/p2p-circuit/p2p/<peer ID>, or /p2p/<peer ID> with libp2p-relays)"
-                );
-            }
-            bail!("{peer} doesn't speak continuum");
-        }
-        let connected = started.elapsed();
-        let mut control = self.control.clone();
-        let body = message.body.clone();
-        let write = async move {
-            let mut stream = control.open_stream(peer, PROTOCOL).await?;
-            let opened = started.elapsed();
-            stream.write_all(&(body.len() as u32).to_be_bytes()).await?;
-            stream.write_all(&body).await?;
-            stream.close().await?;
-            // Kept until the peer has closed its side too. Over QUIC, dropping a stream
-            // stops its reading half (STOP_SENDING), and the peer's answer to the
-            // protocol (sent with the first data, `swarm_config`) then fails, and with it
-            // the stream, before the peer has read the message: identify, which reads
-            // its answers, works, while every message is lost. Yamux (TCP) doesn't mind.
-            // Off the send, which is done.
-            tokio::spawn(async move {
-                let mut rest = [0u8; 64];
-                let _ = tokio::time::timeout(STREAM_TIMEOUT, async {
-                    while let Ok(read) = stream.read(&mut rest).await {
-                        if read == 0 {
-                            break;
-                        }
-                    }
-                })
-                .await;
-            });
-            Ok::<_, anyhow::Error>(opened)
-        };
-        let timeout = stream_timeout(message.body.len());
-        let opened = tokio::time::timeout(timeout, write)
-            .await
-            .map_err(|_| anyhow!("sending to {peer} took longer than {timeout:?}"))?
-            .with_context(|| format!("Sending to {peer}"))?;
-        let took = started.elapsed();
-        if took >= SLOW_SEND {
-            // Where a send's time goes: the swarm task (connecting), the stream's protocol
-            // negotiation (opening), or the connection (writing).
-            debug!(
-                peer = %Addressed(SCHEME, &peer),
-                kind = ?message.kind,
-                bytes = message.body.len(),
-                connect_ms = connected.as_secs_f64() * 1000.0,
-                open_ms = (opened - connected).as_secs_f64() * 1000.0,
-                write_ms = (took - opened).as_secs_f64() * 1000.0,
-                "Slow send"
-            );
-        }
-        Ok(())
-    }
-
-    /// Reads inbound streams (`READS` at once) and handles their messages one at a
-    /// time, in the order they were read; PINGs and PONGs at once (`is_probe`).
-    async fn start_consumer(&self, handler: MessageHandler) -> Result<()> {
-        let Some(mut incoming) = self.incoming.lock().await.take() else {
-            bail!("libp2p consumer already started, or this node only relays");
-        };
-        let handler: Arc<HandlerFn> = Arc::from(handler);
-        let (sender, mut received) = mpsc::channel::<(PeerId, ParsedMessage, usize)>(READS);
-        let reads = Arc::new(Semaphore::new(READS));
-        let probes = Arc::clone(&handler);
-        tokio::spawn(async move {
-            while let Some((peer, stream)) = incoming.next().await {
-                let Ok(permit) = Arc::clone(&reads).acquire_owned().await else {
-                    break;
-                };
-                let sender = sender.clone();
-                let probes = Arc::clone(&probes);
-                tokio::spawn(async move {
-                    match read_message(stream).await {
-                        Ok(body) => match wire::decode(&body) {
-                            Ok(message) if is_probe(&message) => {
-                                hand_on_probe(
-                                    SCHEME,
-                                    &probes,
-                                    peer.to_string(),
-                                    message,
-                                    body.len(),
-                                );
-                            }
-                            Ok(message) => {
-                                let _ = sender.send((peer, message, body.len())).await;
-                            }
-                            Err(error) => {
-                                debug!(peer = %Addressed(SCHEME, &peer), error = %error, "Dropping a message that doesn't decode");
-                            }
-                        },
-                        Err(error) => {
-                            debug!(peer = %Addressed(SCHEME, &peer), error = %format!("{error:#}"), "Dropping an unreadable stream");
-                        }
-                    }
-                    drop(permit);
-                });
-            }
-        });
-        while let Some((peer, message, payload_len)) = received.recv().await {
-            if let Err(error) = handler(peer.to_string(), message, payload_len).await {
-                warn!(peer = %Addressed(SCHEME, &peer), error = %format!("{error:#}"), "Failed to process inbound message");
-            }
-        }
-        Ok(())
-    }
-
-    async fn wait_for_exit(&self) -> std::io::Result<std::process::ExitStatus> {
-        let mut stopped = self.stopped.clone();
-        let _ = stopped.wait_for(|stopped| *stopped).await;
-        Err(std::io::Error::other("the libp2p swarm stopped"))
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use std::sync::atomic::{AtomicU64, Ordering};
-
-    use super::*;
-    use crate::document::replica::Epoch;
-    use crate::transport::{HeadsSummary, Status};
-
-    /// Memory ports are process-wide.
-    static NEXT_PORT: AtomicU64 = AtomicU64::new(40_000);
-
-    /// A node on the in-memory transport, listening on a port of its own (or nowhere),
-    /// and its address with its peer ID (or just its peer ID).
-    fn memory_node_with(
-        listen: bool,
-        relays: Vec<Multiaddr>,
-        relay: bool,
-    ) -> (Libp2pTransport, Multiaddr) {
-        let port = NEXT_PORT.fetch_add(1, Ordering::Relaxed);
-        let key = Keypair::generate_ed25519();
-        let address: Multiaddr = format!("/memory/{port}").parse().unwrap();
-        let peer = key.public().to_peer_id();
-        let transport = Libp2pTransport::start(Libp2pConfig {
-            key,
-            listen: if listen {
-                vec![address.clone()]
-            } else {
-                Vec::new()
-            },
-            announce: Vec::new(),
-            relays,
-            relay,
-            continuum: true,
-            mdns: false,
-            upnp: false,
-            ignore: Vec::new(),
-            public: false,
-            memory: true,
-        })
-        .unwrap();
-        let address = if listen {
-            address.with_p2p(peer).unwrap()
-        } else {
-            Multiaddr::empty().with(Protocol::P2p(peer))
-        };
-        (transport, address)
-    }
-
-    fn memory_node() -> (Libp2pTransport, Multiaddr) {
-        memory_node_with(true, Vec::new(), false)
-    }
-
-    fn status() -> ParsedMessage {
-        ParsedMessage::Status(Status {
-            heads: HeadsSummary::of(Vec::new()),
-            epoch: Epoch::GENESIS,
-            epoch_seq: 3,
-            ready: true,
-            syncs_with_you: false,
-            leaving: false,
-        })
-    }
-
-    /// Starts `transport`'s consumer, forwarding what it receives.
-    fn received(
-        transport: Arc<Libp2pTransport>,
-    ) -> mpsc::UnboundedReceiver<(String, ParsedMessage)> {
-        let (sender, receiver) = mpsc::unbounded_channel();
-        tokio::spawn(async move {
-            transport
-                .start_consumer(Box::new(move |from, message, _| {
-                    let sender = sender.clone();
-                    Box::pin(async move {
-                        let _ = sender.send((from, message));
-                        Ok(())
-                    })
-                }))
-                .await
-        });
-        receiver
-    }
-
-    #[tokio::test]
-    async fn messages_both_ways_over_one_connection() {
-        let (a, a_address) = memory_node();
-        let (b, _) = memory_node();
-        let (a, b) = (Arc::new(a), Arc::new(b));
-        let mut at_a = received(Arc::clone(&a));
-        let mut at_b = received(Arc::clone(&b));
-
-        assert_eq!(
-            b.resolve_seed(&a_address.to_string()).await.unwrap(),
-            a.local_id()
-        );
-        b.send_message(a.local_id(), &status()).await.unwrap();
-        let (from, message) = at_a.recv().await.unwrap();
-        assert_eq!(from, b.local_id());
-        assert!(matches!(message, ParsedMessage::Status(status) if status.epoch_seq == 3));
-
-        // a knows no address of b, but b's connection is there.
-        a.send_message(b.local_id(), &status()).await.unwrap();
-        let (from, _) = at_b.recv().await.unwrap();
-        assert_eq!(from, a.local_id());
-
-        assert_eq!(a.connection(b.local_id()), Some(Connection::Direct));
-        assert_eq!(b.connection(a.local_id()), Some(Connection::Direct));
-        let stats = a.stats().libp2p.unwrap();
-        assert!(stats.connections.direct >= 1);
-        assert_eq!(stats.connections.relayed, 0);
-    }
-
-    #[tokio::test]
-    async fn a_seed_without_a_peer_id_is_connected_to_to_find_out() {
-        let (a, a_address) = memory_node();
-        let (b, _) = memory_node();
-        let mut bare = a_address.clone();
-        bare.pop();
-        assert_eq!(
-            b.resolve_seed(&bare.to_string()).await.unwrap(),
-            a.local_id()
-        );
-        // And b now knows where a is.
-        assert_eq!(b.locations(a.local_id()), [a_address.to_string()]);
-    }
-
-    #[tokio::test]
-    async fn listen_addresses_carry_the_peer_id() {
-        let (a, a_address) = memory_node();
-        let deadline = tokio::time::Instant::now() + Duration::from_secs(5);
-        while a.local_addresses().is_empty() && tokio::time::Instant::now() < deadline {
-            tokio::time::sleep(Duration::from_millis(10)).await;
-        }
-        assert_eq!(a.local_addresses(), [a_address.to_string()]);
-        assert_eq!(
-            a.locate(&a_address.to_string()).as_deref(),
-            Some(a.local_id())
-        );
-    }
-
-    /// Waits up to 5 s for `condition`.
-    async fn eventually(mut condition: impl FnMut() -> bool) -> bool {
-        let deadline = tokio::time::Instant::now() + Duration::from_secs(5);
-        while !condition() {
-            if tokio::time::Instant::now() >= deadline {
-                return false;
-            }
-            tokio::time::sleep(Duration::from_millis(10)).await;
-        }
-        true
-    }
-
-    /// A node learns where a peer that dialled it listens (identify), and can then
-    /// pass it on.
-    #[tokio::test]
-    async fn a_dialled_node_learns_where_the_dialler_listens() {
-        let (a, a_address) = memory_node();
-        let (b, b_address) = memory_node();
-        let (a, b) = (Arc::new(a), Arc::new(b));
-        let _at_a = received(Arc::clone(&a));
-        b.resolve_seed(&a_address.to_string()).await.unwrap();
-        b.send_message(a.local_id(), &status()).await.unwrap();
-        let b_id = b.local_id().to_owned();
-        assert!(
-            eventually(|| a.locations(&b_id) == [b_address.to_string()]).await,
-            "a knows {:?} of b",
-            a.locations(&b_id)
-        );
-    }
-
-    #[tokio::test]
-    async fn announced_addresses_are_published_instead() {
-        let key = Keypair::generate_ed25519();
-        let peer = key.public().to_peer_id();
-        let port = NEXT_PORT.fetch_add(1, Ordering::Relaxed);
-        let announced: Multiaddr = "/ip4/203.0.113.7/tcp/9661".parse().unwrap();
-        let transport = Libp2pTransport::start(Libp2pConfig {
-            key,
-            listen: vec![format!("/memory/{port}").parse().unwrap()],
-            announce: vec![announced.clone()],
-            relays: Vec::new(),
-            relay: false,
-            continuum: true,
-            mdns: false,
-            upnp: false,
-            ignore: Vec::new(),
-            public: false,
-            memory: true,
-        })
-        .unwrap();
-        assert_eq!(
-            transport.local_addresses(),
-            [announced.with_p2p(peer).unwrap().to_string()]
-        );
-    }
-
-    #[test]
-    fn address_ranges() {
-        let range = |text: &str| text.parse::<IpRange>().unwrap();
-        let address = |text: &str| text.parse::<Multiaddr>().unwrap();
-        let ranges = [range("10.244.0.0/16"), range("42::/16"), range("192.0.2.7")];
-        for left_out in [
-            "/ip4/10.244.3.2/udp/9661/quic-v1",
-            "/ip6/42:1:a46e:be4a:cb58:e460:bf0:142c/tcp/9661",
-            "/ip4/192.0.2.7/tcp/1",
-        ] {
-            assert!(ignored(&ranges, &address(left_out)), "{left_out}");
-        }
-        for kept in [
-            "/ip4/10.23.1.144/udp/9661/quic-v1",
-            "/ip4/10.245.0.1/tcp/1",
-            "/ip6/2a0a:4cc0:c1:5eb0::1/udp/9661/quic-v1",
-            "/ip4/192.0.2.8/tcp/1",
-            "/dns4/example.org/tcp/1",
-        ] {
-            assert!(!ignored(&ranges, &address(kept)), "{kept}");
-        }
-        // Through a relay: judged by the connection to the relay, not here.
-        let relayed = format!("/ip4/10.244.0.1/tcp/1/p2p/{}/p2p-circuit", peer());
-        assert!(!ignored(&ranges, &address(&relayed)));
-        assert!(range("0.0.0.0/0").contains("203.0.113.1".parse().unwrap()));
-        assert!(!range("0.0.0.0/0").contains("::1".parse().unwrap()));
-        for wrong in ["10.244.0.0/33", "42::/129", "nowhere", "10.0.0.0/x"] {
-            assert!(wrong.parse::<IpRange>().is_err(), "{wrong}");
-        }
-    }
-
-    /// Ranges left out aren't published; announced addresses are, whatever they are.
-    #[test]
-    fn ignored_addresses_are_not_published() {
-        let parse = |text: &str| text.parse::<Multiaddr>().unwrap();
-        let lan = parse("/ip4/10.23.1.5/udp/9663/quic-v1");
-        let vpn = parse("/ip4/10.244.3.2/udp/9663/quic-v1");
-        let mut book = Book {
-            listening: vec![lan.clone(), vpn.clone()],
-            ignored: vec!["10.244.0.0/16".parse().unwrap()],
-            ..Book::default()
-        };
-        assert_eq!(book.direct(), [lan]);
-        book.announced = vec![vpn.clone()];
-        assert_eq!(book.direct(), [vpn]);
-    }
-
-    /// A port forwarded by hand: once AutoNAT found the node dialable at the router's
-    /// address, that is published with the listen addresses; announced ones still win.
-    #[test]
-    fn the_address_autonat_confirmed_is_published() {
-        let parse = |text: &str| text.parse::<Multiaddr>().unwrap();
-        let lan = parse("/ip4/10.23.1.5/udp/9663/quic-v1");
-        let public = parse("/ip4/91.65.180.254/udp/9663/quic-v1");
-        let mut book = Book {
-            listening: vec![lan.clone()],
-            ..Book::default()
-        };
-        assert_eq!(book.direct(), [lan.clone()]);
-        book.public_address = Some(public.clone().with_p2p(peer()).unwrap());
-        assert_eq!(book.direct(), [public.clone(), lan.clone()]);
-        let announced = parse("/dns4/example.org/udp/9663/quic-v1");
-        book.announced = vec![announced.clone()];
-        assert_eq!(book.direct(), [announced]);
-    }
-
-    #[test]
-    fn local_addresses_are_left_out_unless_there_are_only_local_ones() {
-        let parse = |text: &str| text.parse::<Multiaddr>().unwrap();
-        let loopback = parse("/ip4/127.0.0.1/tcp/1");
-        let link = parse("/ip6/fe80::1/tcp/1");
-        let lan = parse("/ip4/192.168.1.2/tcp/1");
-        let wireguard = parse("/ip6/fd00::2/tcp/1");
-        assert_eq!(
-            published(&[
-                loopback.clone(),
-                link.clone(),
-                lan.clone(),
-                wireguard.clone()
-            ]),
-            [lan, wireguard]
-        );
-        assert_eq!(
-            published(&[loopback.clone(), link.clone()]),
-            [loopback, link]
-        );
-    }
-
-    /// b listens nowhere but through the relay r; a reaches it there.
-    #[tokio::test]
-    async fn a_node_nobody_can_dial_is_reached_through_a_relay() {
-        let (_r, r_address) = memory_node_with(true, Vec::new(), true);
-        let (b, _) = memory_node_with(false, vec![r_address.clone()], false);
-        let b = Arc::new(b);
-        let mut at_b = received(Arc::clone(&b));
-        assert!(
-            eventually(|| !b.local_addresses().is_empty()).await,
-            "b got no slot on the relay"
-        );
-        let relayed = b.local_addresses()[0].clone();
-        assert!(
-            relayed.starts_with(&format!("{r_address}/p2p-circuit/")),
-            "{relayed}"
-        );
-
-        assert!(eventually(|| b.stats().libp2p.unwrap().relay_slots.held == 1).await);
-        let slots = b.stats().libp2p.unwrap().relay_slots;
-        assert_eq!((slots.granted, slots.not_granted), (1, 0));
-
-        let (a, _) = memory_node();
-        assert_eq!(a.resolve_seed(&relayed).await.unwrap(), b.local_id());
-        a.send_message(b.local_id(), &status()).await.unwrap();
-        let (from, _) = at_b.recv().await.unwrap();
-        assert_eq!(from, a.local_id());
-        assert!(a.connection(b.local_id()).is_some());
-    }
-
-    /// A seed that's a peer ID only is reached through the relays the node knows.
-    #[tokio::test]
-    async fn a_peer_id_seed_is_reached_through_a_relay() {
-        let (_r, r_address) = memory_node_with(true, Vec::new(), true);
-        let (b, _) = memory_node_with(false, vec![r_address.clone()], false);
-        let b = Arc::new(b);
-        let mut at_b = received(Arc::clone(&b));
-        assert!(
-            eventually(|| !b.local_addresses().is_empty()).await,
-            "b got no slot on the relay"
-        );
-        let (a, _) = memory_node_with(true, vec![r_address.clone()], false);
-        let seed = format!("/p2p/{}", b.local_id());
-        assert_eq!(a.resolve_seed(&seed).await.unwrap(), b.local_id());
-        assert_eq!(a.resolve_seed(b.local_id()).await.unwrap(), b.local_id());
-        // Nothing to dial is remembered.
-        assert!(!lock(&a.book).addresses.contains_key(&b.peer_id));
-        a.send_message(b.local_id(), &status()).await.unwrap();
-        let (from, _) = at_b.recv().await.unwrap();
-        assert_eq!(from, a.local_id());
-
-        // Without a relay, there's nowhere to look.
-        let (c, _) = memory_node();
-        assert!(c.resolve_seed(&seed).await.is_err());
-    }
-
-    /// b listens nowhere; a, which can be dialled, reaches it through the relay r: b
-    /// then dials a directly (identify told it where), and both keep that.
-    #[tokio::test]
-    async fn a_relayed_connection_is_upgraded_where_one_side_can_be_dialled() {
-        let (_r, r_address) = memory_node_with(true, Vec::new(), true);
-        let (b, _) = memory_node_with(false, vec![r_address.clone()], false);
-        let b = Arc::new(b);
-        let mut at_b = received(Arc::clone(&b));
-        assert!(
-            eventually(|| !b.local_addresses().is_empty()).await,
-            "b got no slot on the relay"
-        );
-        let (a, _) = memory_node();
-        let relayed = b.local_addresses()[0].clone();
-        assert_eq!(a.resolve_seed(&relayed).await.unwrap(), b.local_id());
-        a.send_message(b.local_id(), &status()).await.unwrap();
-        at_b.recv().await.unwrap();
-        assert!(
-            eventually(|| b.connection(a.local_id()) == Some(Connection::Direct)).await,
-            "b didn't dial a directly"
-        );
-        assert_eq!(a.connection(b.local_id()), Some(Connection::Direct));
-        // The relayed one goes (`DUPLICATE_GRACE`); the direct one stays.
-        let deadline = tokio::time::Instant::now() + DUPLICATE_GRACE * 2;
-        while a.stats().libp2p.unwrap().connections.relayed > 0 {
-            assert!(
-                tokio::time::Instant::now() < deadline,
-                "the relayed connection stayed"
-            );
-            tokio::time::sleep(Duration::from_millis(100)).await;
-        }
-        b.send_message(a.local_id(), &status()).await.unwrap();
-        assert_eq!(a.connection(b.local_id()), Some(Connection::Direct));
-    }
-
-    /// A relay that is no node (`--relay-only`) relays, and takes no messages itself.
-    #[tokio::test]
-    async fn a_relay_that_is_no_node() {
-        let port = NEXT_PORT.fetch_add(1, Ordering::Relaxed);
-        let key = Keypair::generate_ed25519();
-        let r_peer = key.public().to_peer_id();
-        let r_listen: Multiaddr = format!("/memory/{port}").parse().unwrap();
-        let r = Libp2pTransport::start(Libp2pConfig {
-            key,
-            listen: vec![r_listen.clone()],
-            announce: Vec::new(),
-            relays: Vec::new(),
-            relay: true,
-            continuum: false,
-            mdns: false,
-            upnp: false,
-            ignore: Vec::new(),
-            public: false,
-            memory: true,
-        })
-        .unwrap();
-        let r_address = r_listen.with_p2p(r_peer).unwrap();
-        let (b, _) = memory_node_with(false, vec![r_address.clone()], false);
-        let b = Arc::new(b);
-        let mut at_b = received(Arc::clone(&b));
-        assert!(
-            eventually(|| !b.local_addresses().is_empty()).await,
-            "b got no slot on the relay"
-        );
-        let (a, _) = memory_node();
-        let relayed = b.local_addresses()[0].clone();
-        assert_eq!(a.resolve_seed(&relayed).await.unwrap(), b.local_id());
-        a.send_message(b.local_id(), &status()).await.unwrap();
-        let (from, _) = at_b.recv().await.unwrap();
-        assert_eq!(from, a.local_id());
-
-        // The relay itself doesn't speak continuum: it takes no messages, and a send to
-        // it is refused once identify has told (the relay's own refusal comes too late:
-        // the protocol goes with the first data, `swarm_config`), saying what to give
-        // as a seed instead.
-        assert_eq!(
-            a.resolve_seed(&r_address.to_string()).await.unwrap(),
-            r.local_id()
-        );
-        assert!(
-            eventually(|| lock(&a.book).not_nodes.get(&r.peer_id) == Some(&true)).await,
-            "identify didn't tell"
-        );
-        let refused = a.send_message(r.local_id(), &status()).await.unwrap_err();
-        assert!(
-            refused.to_string().contains("is a relay, not a node"),
-            "{refused:#}"
-        );
-        assert!(
-            r.start_consumer(Box::new(|_, _, _| Box::pin(async { Ok(()) })))
-                .await
-                .is_err()
-        );
-    }
-
-    /// A relay configured without its peer ID is found out, and used.
-    #[tokio::test]
-    async fn a_relay_configured_without_its_peer_id() {
-        let (_r, r_address) = memory_node_with(true, Vec::new(), true);
-        let mut bare = r_address.clone();
-        bare.pop();
-        let (b, _) = memory_node_with(false, vec![bare], false);
-        assert!(
-            eventually(|| !b.local_addresses().is_empty()).await,
-            "b got no slot on the relay"
-        );
-        assert!(b.local_addresses()[0].starts_with(&format!("{r_address}/p2p-circuit/")));
-    }
-
-    fn peer() -> PeerId {
-        Keypair::generate_ed25519().public().to_peer_id()
-    }
-
-    #[test]
-    fn relays_are_picked_when_needed() {
-        use ::libp2p::autonat::NatStatus;
-        let local = peer();
-        let offers: HashMap<PeerId, Multiaddr> = (0..4)
-            .map(|port| (peer(), format!("/memory/{port}").parse().unwrap()))
-            .collect();
-        let check = |direct, nat: &NatStatus, using: &[PeerId]| {
-            relay_check(local, direct, nat, &offers, using)
-        };
-        // Dialable, or not known yet with an address to dial: none.
-        assert!(check(true, &NatStatus::Public(Multiaddr::empty()), &[]).is_empty());
-        assert!(check(false, &NatStatus::Public(Multiaddr::empty()), &[]).is_empty());
-        assert!(check(true, &NatStatus::Unknown, &[]).is_empty());
-        // No address to dial, or AutoNAT says it can't be dialled: some.
-        assert_eq!(check(false, &NatStatus::Unknown, &[]).len(), AUTO_RELAYS);
-        let picked = check(true, &NatStatus::Private, &[]);
-        assert_eq!(picked.len(), AUTO_RELAYS);
-        // One in use: the next in the same order.
-        let more = check(true, &NatStatus::Private, &[picked[0].0]);
-        assert_eq!(more.len(), AUTO_RELAYS - 1);
-        assert_eq!(more[0].0, picked[1].0);
-        let all: Vec<PeerId> = picked.iter().map(|(relay, _)| *relay).collect();
-        assert!(check(true, &NatStatus::Private, &all).is_empty());
-        // Never itself.
-        let only_us = HashMap::from([(local, Multiaddr::empty())]);
-        assert!(relay_check(local, false, &NatStatus::Private, &only_us, &[]).is_empty());
-    }
-
-    /// A relay says so in its addresses; b, which nobody can dial, learns of it (as from
-    /// the member list) and becomes reachable through it.
-    #[tokio::test]
-    async fn a_member_that_relays_is_picked() {
-        let (r, _) = memory_node_with(true, Vec::new(), true);
-        assert!(eventually(|| !r.local_addresses().is_empty()).await);
-        let offer = r
-            .local_addresses()
-            .into_iter()
-            .find(|address| address.ends_with("/p2p-circuit"))
-            .expect("the relay offers itself");
-        let (b, _) = memory_node_with(false, Vec::new(), false);
-        assert_eq!(b.locate(&offer).as_deref(), Some(r.local_id()));
-        assert!(
-            eventually(|| b
-                .local_addresses()
-                .iter()
-                .any(|address| address.contains("/p2p-circuit/")))
-            .await,
-            "b isn't reachable through r: {:?}",
-            b.local_addresses()
-        );
-    }
-
-    /// A peer on the LAN that speaks continuum becomes a seed once, at its address.
-    #[test]
-    fn lan_peers_become_seeds_once() {
-        let mut book = Book::default();
-        let lan = peer();
-        let address: Multiaddr = "/ip4/192.168.1.5/tcp/9661".parse().unwrap();
-        book.discover(lan); // No address known: nothing.
-        assert!(book.discovered.is_empty());
-        book.remember(lan, address.clone());
-        book.discover(lan);
-        book.discover(lan);
-        assert_eq!(book.discovered, [address.with_p2p(lan).unwrap()]);
-    }
-
-    #[test]
-    fn named_relays() {
-        let (local, r1, r2) = (peer(), peer(), peer());
-        let at = |port: u16| -> Multiaddr { format!("/ip6/fd00::1/tcp/{port}").parse().unwrap() };
-        let mut book = Book::default();
-        // With a peer ID: known at once; without: to be found out, once.
-        assert_eq!(
-            book.name_relay(at(1).with_p2p(r1).unwrap(), Named::Configured, local),
-            None
-        );
-        assert_eq!(
-            book.name_relay(at(2), Named::Configured, local),
-            Some(at(2))
-        );
-        assert_eq!(book.name_relay(at(2), Named::Configured, local), None);
-        assert_eq!(
-            book.name_relay(at(3).with_p2p(local).unwrap(), Named::Configured, local),
-            None
-        );
-        assert!(book.relay_found(at(2), r2, local));
-        assert_eq!(book.named(Named::Configured).len(), 2);
-        // A relay named with its peer ID isn't found out again; one without is.
-        assert_eq!(book.find_again(r1), None);
-        assert_eq!(book.find_again(r2), Some(at(2)));
-        assert!(!book.named(Named::Configured).contains_key(&r2));
-
-        // Listed: configured wins; unlisted ones go, unless also configured.
-        let r3 = peer();
-        let listed = vec![
-            at(1).with_p2p(r1).unwrap(),
-            at(4).with_p2p(r3).unwrap(),
-            at(5),
-        ];
-        assert_eq!(book.learn_listed(listed.clone(), local), Some(vec![at(5)]));
-        assert_eq!(book.learn_listed(listed, local), None);
-        assert_eq!(book.named_relays[&r1].named, Named::Configured);
-        assert_eq!(book.named(Named::Listed).keys().collect::<Vec<_>>(), [&r3]);
-        assert_eq!(book.learn_listed(Vec::new(), local), Some(Vec::new()));
-        assert!(book.named(Named::Listed).is_empty());
-        assert!(!book.finding.contains_key(&at(5)));
-        assert!(!book.relay_found(at(5), peer(), local)); // No longer listed.
-        assert_eq!(book.named(Named::Configured).len(), 1);
-    }
-
-    #[test]
-    fn known_addresses() {
-        let mut book = Book::default();
-        let (relay, us) = (peer(), peer());
-        let direct: Multiaddr = "/ip6/fd00::1/tcp/9661".parse().unwrap();
-        let relayed: Multiaddr = format!("/ip6/fd00::2/tcp/9661/p2p/{relay}/p2p-circuit/p2p/{us}")
-            .parse()
-            .unwrap();
-        assert!(!book.knows(us, &[direct.clone()]));
-        book.remember(us, relayed.clone());
-        book.remember(us, direct.clone());
-        // In any order, with or without the peer ID.
-        assert!(book.knows(us, &[relayed.clone(), direct.clone()]));
-        assert!(book.knows(us, &[direct.clone().with_p2p(us).unwrap()]));
-        assert!(!book.knows(us, &["/ip6/fd00::3/tcp/9661".parse().unwrap()]));
-    }
-
-    /// Peers nobody mentions any more are forgotten, but connected ones.
-    #[test]
-    fn stale_peers_are_forgotten() {
-        let (old, current, connected) = (peer(), peer(), peer());
-        let address: Multiaddr = "/ip6/fd00::1/tcp/9661".parse().unwrap();
-        let mut book = Book::default();
-        for peer in [old, current, connected] {
-            book.remember(peer, address.clone());
-        }
-        book.relays.insert(old, address.clone());
-        book.continuum.insert(old);
-        // From after the mentions above (taken at `Instant::now()`), however fast or
-        // slow the clock moved meanwhile.
-        let later = tokio::time::Instant::now() + STALE_AFTER;
-        // `current` was mentioned again since.
-        book.seen.insert(current, later);
-        assert_eq!(book.prune(later, |peer| *peer == connected), 1);
-        assert!(!book.addresses.contains_key(&old));
-        assert!(!book.relays.contains_key(&old) && !book.continuum.contains(&old));
-        assert!(book.addresses.contains_key(&current));
-        assert!(book.addresses.contains_key(&connected));
-        assert_eq!(book.prune(later, |_| false), 1); // `connected`, once it isn't.
-    }
-
-    #[test]
-    fn relay_failures_are_short() {
-        assert_eq!(
-            relay_failure_text(
-                "Custom { kind: Other, error: Other(Left(Left(Left(Reservation(Protocol(NoAddressesInReservation)))))) }",
-                "x"
-            ),
-            "the relay gave no address to be reached through it"
-        );
-        assert_eq!(
-            relay_failure_text(
-                "Codec(Error(Custom { kind: Other, error: Failed }))",
-                "Failed"
-            ),
-            "the relay refused the circuit relay protocol (is it a relay?)"
-        );
-        assert_eq!(
-            relay_failure_text("Io(…)", "connection reset"),
-            "connection reset"
-        );
-        assert_eq!(relay_failure(&Ok(())), "closed");
-    }
-
-    /// Only refusals pause a relay; a slot that ended otherwise is asked for again.
-    #[test]
-    fn only_refusals_pause_relays() {
-        let refused = [
-            ("Reservation(Protocol(NoAddressesInReservation))", "x"),
-            ("Reservation(Status(ResourceLimitExceeded))", "x"),
-            ("Reservation(Status(PermissionDenied))", "x"),
-            ("Denied { cause: \"connection gated\" }", "x"),
-            ("Upgrade(UnsupportedProtocol)", "x"),
-            ("Dial(WrongPeerId { obtained: … })", "x"),
-            (
-                "Codec(Error(Custom { kind: Other, error: Failed }))",
-                "Failed",
-            ),
-        ];
-        for (debug, innermost) in refused {
-            assert!(relay_refused(debug, innermost), "{debug}");
-        }
-        let not = [
-            ("Io(Custom { kind: Other, error: Timeout })", "Timeout"),
-            (
-                "Io(Custom { kind: Other, error: Right(Closed) })",
-                "connection is closed",
-            ),
-            ("Io(…)", "connection reset"),
-        ];
-        for (debug, innermost) in not {
-            assert!(!relay_refused(debug, innermost), "{debug}");
-        }
-    }
-
-    #[test]
-    fn listen_addresses_offered_for_hole_punching() {
-        let parse = |text: &str| text.parse::<Multiaddr>().unwrap();
-        assert!(offered(&parse("/ip4/192.168.1.2/udp/9661/quic-v1")));
-        assert!(offered(&parse("/ip6/fd00::2/tcp/9661")));
-        assert!(!offered(&parse("/ip4/127.0.0.1/udp/9661/quic-v1")));
-        assert!(!offered(&parse("/ip6/fe80::1/tcp/9661")));
-        let relay = PeerId::random();
-        assert!(!offered(&parse(&format!(
-            "/ip4/192.168.1.2/tcp/9661/p2p/{relay}/p2p-circuit"
-        ))));
-    }
-
-    /// libp2p's nested dial errors come out as each address's cause, once.
-    #[test]
-    fn dial_errors_are_short() {
-        use ::libp2p::core::transport::TransportError;
-        let peer = peer();
-        let address: Multiaddr = format!("/ip6/fd00::1/tcp/9661/p2p/{peer}").parse().unwrap();
-        let nested = std::io::Error::other(
-            "Multiple dial errors occurred:\n - Network is unreachable (os error 101): Multiple dial errors occurred:\n - Network is unreachable (os error 101): Network is unreachable (os error 101)",
-        );
-        let error =
-            ::libp2p::swarm::DialError::Transport(vec![(address, TransportError::Other(nested))]);
-        assert_eq!(
-            describe_dial_error(&error),
-            "/ip6/fd00::1/tcp/9661: Network is unreachable (os error 101)"
-        );
-        let refused = ::libp2p::swarm::DialError::Transport(vec![(
-            "/ip4/10.0.0.1/tcp/1".parse().unwrap(),
-            TransportError::Other(std::io::Error::from(std::io::ErrorKind::ConnectionRefused)),
-        )]);
-        assert_eq!(
-            describe_dial_error(&refused),
-            "/ip4/10.0.0.1/tcp/1: connection refused"
-        );
-    }
-
-    /// A relay doesn't dial the nodes it relays for through itself.
-    #[test]
-    fn no_circuits_through_ourselves() {
-        let (us, other_relay, target) = (peer(), peer(), peer());
-        let through = |relay: PeerId| -> Multiaddr {
-            format!("/ip6/fd00::1/tcp/9661/p2p/{relay}/p2p-circuit")
-                .parse()
-                .unwrap()
-        };
-        let direct: Multiaddr = "/ip6/fd00::2/tcp/9661".parse().unwrap();
-        assert_eq!(relay_of(&through(us)), Some(us));
-        assert_eq!(relay_of(&direct), None);
-        assert_eq!(relay_of(&direct.clone().with_p2p(target).unwrap()), None);
-        assert_eq!(
-            dialable(&[through(us), through(other_relay), direct.clone()], us),
-            [through(other_relay), direct]
-        );
-    }
-
-    #[tokio::test]
-    async fn unknown_peers_are_refused() {
-        let (b, _) = memory_node();
-        let stranger = Keypair::generate_ed25519()
-            .public()
-            .to_peer_id()
-            .to_string();
-        assert!(b.send_message(&stranger, &status()).await.is_err());
-        assert!(b.resolve_seed(&stranger).await.is_err());
-        assert_eq!(b.connection(&stranger), None);
-    }
-
-    #[test]
-    fn a_direct_connection_wins_over_a_relayed_one() {
-        let mut book = Book::default();
-        let (relayed_only, both) = (peer(), peer());
-        let mut id = 0;
-        let mut connect = |book: &mut Book, peer: PeerId, relayed: bool| {
-            id += 1;
-            let address: Multiaddr = format!("/ip4/10.0.0.{id}/tcp/1").parse().unwrap();
-            book.connections
-                .insert(ConnectionId::new_unchecked(id), (peer, relayed, address));
-        };
-        connect(&mut book, relayed_only, true);
-        connect(&mut book, both, true);
-        connect(&mut book, both, false);
-        assert_eq!(book.connection(&relayed_only), Some(Connection::Relayed));
-        assert_eq!(book.connection(&both), Some(Connection::Direct));
-        assert_eq!(book.connection(&peer()), None);
-        assert_eq!(
-            book.location(&both).map(|address| address.to_string()),
-            Some("/ip4/10.0.0.3/tcp/1".to_owned())
-        );
-        let connections = book.stats().connections;
-        assert_eq!((connections.direct, connections.relayed), (1, 2));
-        // Of several, the oldest direct one stays; a relayed one only without a direct.
-        connect(&mut book, both, false);
-        assert_eq!(
-            book.duplicates(&both, false),
-            [
-                ConnectionId::new_unchecked(4),
-                ConnectionId::new_unchecked(2)
-            ]
-        );
-        assert!(book.duplicates(&relayed_only, false).is_empty());
-        // Not while one of them carries a slot, ours or the peer's, or we reserve one.
-        assert!(book.duplicates(&both, true).is_empty());
-        book.slots.insert(both);
-        assert!(book.duplicates(&both, false).is_empty());
-        book.slots.clear();
-        book.slots_here.insert(both);
-        assert!(book.duplicates(&both, false).is_empty());
-        book.slots_here.clear();
-        // Once measured, the fastest direct one stays, however young.
-        book.rtts
-            .insert(ConnectionId::new_unchecked(3), Duration::from_millis(40));
-        book.rtts
-            .insert(ConnectionId::new_unchecked(4), Duration::from_millis(2));
-        assert_eq!(
-            book.duplicates(&both, false),
-            [
-                ConnectionId::new_unchecked(3),
-                ConnectionId::new_unchecked(2)
-            ]
-        );
-        assert_eq!(
-            book.location(&both).map(|address| address.to_string()),
-            Some("/ip4/10.0.0.4/tcp/1".to_owned())
-        );
-    }
-}