feat: ephemeral peer channels (#5346)

Co-authored-by: link2xt <link2xt@testrun.org>
Co-authored-by: iequidoo <117991069+iequidoo@users.noreply.github.com>

src/peer_channels.rs

@@ -0,0 +1,711 @@
+//! Peer channels for realtime communication in webxdcs.
+//!
+//! We use Iroh as an ephemeral peer channels provider to create direct communication
+//! channels between webxdcs. See [here](https://webxdc.org/docs/spec/joinRealtimeChannel.html) for the webxdc specs.
+//!
+//! Ephemeral channels should be established lazily, to avoid bootstrapping p2p connectivity
+//! when it's not required. Only when a webxdc subscribes to realtime data or when a reatlime message is sent,
+//! the p2p machinery should be started.
+//!
+//! Adding peer channels to webxdc needs upfront negotation of a topic and sharing of public keys so that
+//! nodes can connect to each other. The explicit approach is as follows:
+//!
+//! 1. We introduce a new [GossipTopic](crate::headerdef::HeaderDef::IrohGossipTopic) message header with a random 32-byte TopicId,
+//!    securely generated on the initial webxdc sender's device. This message header is encrypted
+//!    and sent in the same message as the webxdc application.
+//! 2. Whenever `joinRealtimeChannel().setListener()` or `joinRealtimeChannel().send()` is called by the webxdc application,
+//!    we start a routine to establish p2p connectivity and join the gossip swarm with Iroh.
+//! 3. The first step of this routine is to introduce yourself with a regular message containing the `IrohPublicKey`.
+//!    This message contains the users relay-server and public key.
+//!    Direct IP address is not included as this information can be persisted by email providers.
+//! 4. After the announcement, the sending peer joins the gossip swarm with an empty list of peer IDs (as they don't know anyone yet).
+//! 5. Upon receiving an announcement message, other peers store the sender's [NodeAddr] in the database
+//!    (scoped per WebXDC app instance/message-id). The other peers can then join the gossip with `joinRealtimeChannel().setListener()`
+//!    and `joinRealtimeChannel().send()` just like the other peers.
+
+use anyhow::{anyhow, Context as _, Result};
+use email::Header;
+use iroh_gossip::net::{Gossip, JoinTopicFut, GOSSIP_ALPN};
+use iroh_gossip::proto::{Event as IrohEvent, TopicId};
+use iroh_net::relay::{RelayMap, RelayUrl};
+use iroh_net::{key::SecretKey, relay::RelayMode, MagicEndpoint};
+use iroh_net::{NodeAddr, NodeId};
+use std::collections::{BTreeSet, HashMap};
+use std::env;
+use tokio::sync::RwLock;
+use tokio::task::JoinHandle;
+use url::Url;
+
+use crate::chat::send_msg;
+use crate::context::Context;
+use crate::headerdef::HeaderDef;
+use crate::message::{Message, MsgId, Viewtype};
+use crate::mimeparser::SystemMessage;
+use crate::EventType;
+
+/// The length of an ed25519 `PublicKey`, in bytes.
+const PUBLIC_KEY_LENGTH: usize = 32;
+const PUBLIC_KEY_STUB: &[u8] = "static_string".as_bytes();
+
+/// Store iroh peer channels for the context.
+#[derive(Debug)]
+pub struct Iroh {
+    /// [MagicEndpoint] needed for iroh peer channels.
+    pub(crate) endpoint: MagicEndpoint,
+
+    /// [Gossip] needed for iroh peer channels.
+    pub(crate) gossip: Gossip,
+
+    /// Topics for which an advertisement has already been sent.
+    pub(crate) iroh_channels: RwLock<HashMap<TopicId, ChannelState>>,
+
+    /// Currently used Iroh secret key
+    pub(crate) secret_key: SecretKey,
+}
+
+impl Iroh {
+    /// Notify the endpoint that the network has changed.
+    pub(crate) async fn network_change(&self) {
+        self.endpoint.network_change().await
+    }
+
+    /// Join a topic and create the subscriber loop for it.
+    ///
+    /// If there is no gossip, create it.
+    ///
+    /// The returned future resolves when the swarm becomes operational.
+    async fn join_and_subscribe_gossip(
+        &self,
+        ctx: &Context,
+        msg_id: MsgId,
+    ) -> Result<Option<JoinTopicFut>> {
+        let topic = get_iroh_topic_for_msg(ctx, msg_id).await?;
+        let seq = if let Some(channel_state) = self.iroh_channels.read().await.get(&topic) {
+            if channel_state.subscribe_loop.is_some() {
+                return Ok(None);
+            }
+            channel_state.seq_number
+        } else {
+            0
+        };
+
+        let peers = get_iroh_gossip_peers(ctx, msg_id).await?;
+        info!(
+            ctx,
+            "IROH_REALTIME: Joining gossip with peers: {:?}",
+            peers.iter().map(|p| p.node_id).collect::<Vec<_>>()
+        );
+
+        // Connect to all peers
+        for peer in &peers {
+            self.endpoint.add_node_addr(peer.clone())?;
+        }
+
+        let connect_future = self
+            .gossip
+            .join(topic, peers.into_iter().map(|addr| addr.node_id).collect())
+            .await?;
+
+        let ctx = ctx.clone();
+        let gossip = self.gossip.clone();
+        let subscribe_loop = tokio::spawn(async move {
+            if let Err(e) = subscribe_loop(&ctx, gossip, topic, msg_id).await {
+                warn!(ctx, "subscribe_loop failed: {e}")
+            }
+        });
+
+        self.iroh_channels
+            .write()
+            .await
+            .insert(topic, ChannelState::new(seq, subscribe_loop));
+
+        Ok(Some(connect_future))
+    }
+
+    /// Send realtime data to the gossip swarm.
+    pub async fn send_webxdc_realtime_data(
+        &self,
+        ctx: &Context,
+        msg_id: MsgId,
+        mut data: Vec<u8>,
+    ) -> Result<()> {
+        let topic = get_iroh_topic_for_msg(ctx, msg_id).await?;
+        self.join_and_subscribe_gossip(ctx, msg_id).await?;
+
+        let seq_num = self.get_and_incr(&topic).await;
+        data.extend(seq_num.to_le_bytes());
+        data.extend(self.secret_key.public().as_bytes());
+
+        self.gossip.broadcast(topic, data.into()).await?;
+
+        if env::var("REALTIME_DEBUG").is_ok() {
+            info!(ctx, "Sent realtime data");
+        }
+
+        Ok(())
+    }
+
+    async fn get_and_incr(&self, topic: &TopicId) -> i32 {
+        let mut seq = 0;
+        if let Some(state) = self.iroh_channels.write().await.get_mut(topic) {
+            seq = state.seq_number;
+            state.seq_number = state.seq_number.wrapping_add(1)
+        }
+        seq
+    }
+
+    /// Get the iroh [NodeAddr] without direct IP addresses.
+    pub(crate) async fn get_node_addr(&self) -> Result<NodeAddr> {
+        let mut addr = self.endpoint.my_addr().await?;
+        addr.info.direct_addresses = BTreeSet::new();
+        Ok(addr)
+    }
+
+    /// Leave the realtime channel for a given topic.
+    pub(crate) async fn leave_realtime(&self, topic: TopicId) -> Result<()> {
+        if let Some(channel) = &mut self.iroh_channels.write().await.get_mut(&topic) {
+            if let Some(subscribe_loop) = channel.subscribe_loop.take() {
+                subscribe_loop.abort();
+            }
+        }
+        self.gossip.quit(topic).await?;
+        Ok(())
+    }
+}
+
+/// Single gossip channel state.
+#[derive(Debug)]
+pub(crate) struct ChannelState {
+    /// Sequence number for the gossip channel.
+    seq_number: i32,
+    /// The subscribe loop handle.
+    subscribe_loop: Option<JoinHandle<()>>,
+}
+
+impl ChannelState {
+    fn new(seq_number: i32, subscribe_loop: JoinHandle<()>) -> Self {
+        Self {
+            seq_number,
+            subscribe_loop: Some(subscribe_loop),
+        }
+    }
+}
+
+impl Context {
+    /// Create magic endpoint and gossip.
+    async fn init_peer_channels(&self) -> Result<Iroh> {
+        let secret_key: SecretKey = SecretKey::generate();
+
+        let relay_mode = if let Some(relay_url) = self
+            .metadata
+            .read()
+            .await
+            .as_ref()
+            .and_then(|conf| conf.iroh_relay.clone())
+        {
+            RelayMode::Custom(RelayMap::from_url(RelayUrl::from(relay_url)))
+        } else {
+            // FIXME: this should be RelayMode::Disabled instead.
+            // Currently using default relays because otherwise Rust tests fail.
+            RelayMode::Default
+        };
+
+        let endpoint = MagicEndpoint::builder()
+            .secret_key(secret_key.clone())
+            .alpns(vec![GOSSIP_ALPN.to_vec()])
+            .relay_mode(relay_mode)
+            .bind(0)
+            .await?;
+
+        // create gossip
+        let my_addr = endpoint.my_addr().await?;
+        let gossip = Gossip::from_endpoint(endpoint.clone(), Default::default(), &my_addr.info);
+
+        // spawn endpoint loop that forwards incoming connections to the gossiper
+        let context = self.clone();
+
+        // Shuts down on deltachat shutdown
+        tokio::spawn(endpoint_loop(context, endpoint.clone(), gossip.clone()));
+
+        Ok(Iroh {
+            endpoint,
+            gossip,
+            iroh_channels: RwLock::new(HashMap::new()),
+            secret_key,
+        })
+    }
+
+    /// Get or initialize the iroh peer channel.
+    pub async fn get_or_try_init_peer_channel(&self) -> Result<&Iroh> {
+        let ctx = self.clone();
+        self.iroh
+            .get_or_try_init(|| async { ctx.init_peer_channels().await })
+            .await
+    }
+}
+
+/// Cache a peers [NodeId] for one topic.
+pub(crate) async fn iroh_add_peer_for_topic(
+    ctx: &Context,
+    msg_id: MsgId,
+    topic: TopicId,
+    peer: NodeId,
+    relay_server: Option<&str>,
+) -> Result<()> {
+    ctx.sql
+        .execute(
+            "INSERT OR REPLACE INTO iroh_gossip_peers (msg_id, public_key, topic, relay_server) VALUES (?, ?, ?, ?)",
+            (msg_id, peer.as_bytes(), topic.as_bytes(), relay_server),
+        )
+        .await?;
+    Ok(())
+}
+
+/// Insert topicId into the database so that we can use it to retrieve the topic.
+pub(crate) async fn insert_topic_stub(ctx: &Context, msg_id: MsgId, topic: TopicId) -> Result<()> {
+    ctx.sql
+        .execute(
+            "INSERT OR REPLACE INTO iroh_gossip_peers (msg_id, public_key, topic, relay_server) VALUES (?, ?, ?, ?)",
+            (msg_id, PUBLIC_KEY_STUB, topic.as_bytes(), Option::<&str>::None),
+        )
+        .await?;
+    Ok(())
+}
+
+/// Get a list of [NodeAddr]s for one webxdc.
+async fn get_iroh_gossip_peers(ctx: &Context, msg_id: MsgId) -> Result<Vec<NodeAddr>> {
+    ctx.sql
+        .query_map(
+            "SELECT public_key, relay_server FROM iroh_gossip_peers WHERE msg_id = ? AND public_key != ?",
+            (msg_id, PUBLIC_KEY_STUB),
+            |row| {
+                let key:  Vec<u8> = row.get(0)?;
+                let server: Option<String> = row.get(1)?;
+                Ok((key, server))
+            },
+            |g| {
+                g.map(|data| {
+                    let (key, server) = data?;
+                    let server = server.map(|data| Ok::<_, url::ParseError>(RelayUrl::from(Url::parse(&data)?))).transpose()?;
+                    let id = NodeId::from_bytes(&key.try_into()
+                    .map_err(|_| anyhow!("Can't convert sql data to [u8; 32]"))?)?;
+                    Ok::<_, anyhow::Error>(NodeAddr::from_parts(
+                        id, server, vec![]
+                    ))
+                })
+                .collect::<std::result::Result<Vec<_>, _>>()
+                .map_err(Into::into)
+            },
+        )
+        .await
+}
+
+/// Get the topic for a given [MsgId].
+pub(crate) async fn get_iroh_topic_for_msg(ctx: &Context, msg_id: MsgId) -> Result<TopicId> {
+    let bytes: Vec<u8> = ctx
+        .sql
+        .query_get_value(
+            "SELECT topic FROM iroh_gossip_peers WHERE msg_id = ? LIMIT 1",
+            (msg_id,),
+        )
+        .await?
+        .context("couldn't restore topic from db")?;
+    Ok(TopicId::from_bytes(bytes.try_into().unwrap()))
+}
+
+/// Send a gossip advertisement to the chat that [MsgId] belongs to.
+/// This method should be called from the frontend when `joinRealtimeChannel` is called.
+pub async fn send_webxdc_realtime_advertisement(
+    ctx: &Context,
+    msg_id: MsgId,
+) -> Result<Option<JoinTopicFut>> {
+    let iroh = ctx.get_or_try_init_peer_channel().await?;
+    let conn = iroh.join_and_subscribe_gossip(ctx, msg_id).await?;
+
+    let webxdc = Message::load_from_db(ctx, msg_id).await?;
+    let mut msg = Message::new(Viewtype::Text);
+    msg.hidden = true;
+    msg.param.set_cmd(SystemMessage::IrohNodeAddr);
+    msg.in_reply_to = Some(webxdc.rfc724_mid.clone());
+    send_msg(ctx, webxdc.chat_id, &mut msg).await?;
+    info!(ctx, "IROH_REALTIME: Sent realtime advertisement");
+    Ok(conn)
+}
+
+/// Send realtime data to the gossip swarm.
+pub async fn send_webxdc_realtime_data(ctx: &Context, msg_id: MsgId, data: Vec<u8>) -> Result<()> {
+    let iroh = ctx.get_or_try_init_peer_channel().await?;
+    iroh.send_webxdc_realtime_data(ctx, msg_id, data).await?;
+    Ok(())
+}
+
+/// Leave the gossip of the webxdc with given [MsgId].
+pub async fn leave_webxdc_realtime(ctx: &Context, msg_id: MsgId) -> Result<()> {
+    let iroh = ctx.get_or_try_init_peer_channel().await?;
+    iroh.leave_realtime(get_iroh_topic_for_msg(ctx, msg_id).await?)
+        .await?;
+    info!(ctx, "IROH_REALTIME: Left gossip for message {msg_id}");
+
+    Ok(())
+}
+
+pub(crate) fn create_random_topic() -> TopicId {
+    TopicId::from_bytes(rand::random())
+}
+
+pub(crate) async fn create_iroh_header(
+    ctx: &Context,
+    topic: TopicId,
+    msg_id: MsgId,
+) -> Result<Header> {
+    insert_topic_stub(ctx, msg_id, topic).await?;
+    Ok(Header::new(
+        HeaderDef::IrohGossipTopic.get_headername().to_string(),
+        topic.to_string(),
+    ))
+}
+
+async fn endpoint_loop(context: Context, endpoint: MagicEndpoint, gossip: Gossip) {
+    while let Some(conn) = endpoint.accept().await {
+        info!(context, "IROH_REALTIME: accepting iroh connection");
+        let gossip = gossip.clone();
+        let context = context.clone();
+        tokio::spawn(async move {
+            if let Err(err) = handle_connection(&context, conn, gossip).await {
+                warn!(context, "IROH_REALTIME: iroh connection error: {err}");
+            }
+        });
+    }
+}
+
+async fn handle_connection(
+    context: &Context,
+    mut conn: iroh_net::magic_endpoint::Connecting,
+    gossip: Gossip,
+) -> anyhow::Result<()> {
+    let alpn = conn.alpn().await?;
+    let conn = conn.await?;
+    let peer_id = iroh_net::magic_endpoint::get_remote_node_id(&conn)?;
+
+    match alpn.as_bytes() {
+        GOSSIP_ALPN => gossip
+            .handle_connection(conn)
+            .await
+            .context(format!("Connection to {peer_id} with ALPN {alpn} failed"))?,
+        _ => warn!(
+            context,
+            "Ignoring connection from {peer_id}: unsupported ALPN protocol"
+        ),
+    }
+    Ok(())
+}
+
+async fn subscribe_loop(
+    context: &Context,
+    gossip: Gossip,
+    topic: TopicId,
+    msg_id: MsgId,
+) -> Result<()> {
+    let mut stream = gossip.subscribe(topic).await?;
+    loop {
+        let event = stream.recv().await?;
+        match event {
+            IrohEvent::NeighborUp(node) => {
+                info!(context, "IROH_REALTIME: NeighborUp: {}", node.to_string());
+                iroh_add_peer_for_topic(context, msg_id, topic, node, None).await?;
+            }
+            IrohEvent::Received(event) => {
+                info!(context, "IROH_REALTIME: Received realtime data");
+                context.emit_event(EventType::WebxdcRealtimeData {
+                    msg_id,
+                    data: event
+                        .content
+                        .get(0..event.content.len() - 4 - PUBLIC_KEY_LENGTH)
+                        .context("too few bytes in iroh message")?
+                        .into(),
+                });
+            }
+            _ => (),
+        };
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::{
+        chat::send_msg,
+        message::{Message, Viewtype},
+        peer_channels::{
+            get_iroh_gossip_peers, get_iroh_topic_for_msg, leave_webxdc_realtime,
+            send_webxdc_realtime_advertisement,
+        },
+        test_utils::TestContextManager,
+        EventType,
+    };
+
+    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+    async fn test_can_communicate() {
+        let mut tcm = TestContextManager::new();
+        let alice = &mut tcm.alice().await;
+        let bob = &mut tcm.bob().await;
+
+        // Alice sends webxdc to bob
+        let alice_chat = alice.create_chat(bob).await;
+        let mut instance = Message::new(Viewtype::File);
+        instance
+            .set_file_from_bytes(
+                alice,
+                "minimal.xdc",
+                include_bytes!("../test-data/webxdc/minimal.xdc"),
+                None,
+            )
+            .await
+            .unwrap();
+
+        send_msg(alice, alice_chat.id, &mut instance).await.unwrap();
+        let alice_webxdc = alice.get_last_msg().await;
+        assert_eq!(alice_webxdc.get_viewtype(), Viewtype::Webxdc);
+
+        let webxdc = alice.pop_sent_msg().await;
+        let bob_webdxc = bob.recv_msg(&webxdc).await;
+        assert_eq!(bob_webdxc.get_viewtype(), Viewtype::Webxdc);
+
+        bob_webdxc.chat_id.accept(bob).await.unwrap();
+
+        // Alice advertises herself.
+        send_webxdc_realtime_advertisement(alice, alice_webxdc.id)
+            .await
+            .unwrap();
+
+        bob.recv_msg_trash(&alice.pop_sent_msg().await).await;
+        let bob_iroh = bob.get_or_try_init_peer_channel().await.unwrap();
+
+        // Bob adds alice to gossip peers.
+        let members = get_iroh_gossip_peers(bob, bob_webdxc.id)
+            .await
+            .unwrap()
+            .into_iter()
+            .map(|addr| addr.node_id)
+            .collect::<Vec<_>>();
+
+        let alice_iroh = alice.get_or_try_init_peer_channel().await.unwrap();
+        assert_eq!(
+            members,
+            vec![alice_iroh.get_node_addr().await.unwrap().node_id]
+        );
+
+        bob_iroh
+            .join_and_subscribe_gossip(bob, bob_webdxc.id)
+            .await
+            .unwrap()
+            .unwrap()
+            .await
+            .unwrap();
+
+        // Alice sends ephemeral message
+        alice_iroh
+            .send_webxdc_realtime_data(alice, alice_webxdc.id, "alice -> bob".as_bytes().to_vec())
+            .await
+            .unwrap();
+
+        loop {
+            let event = bob.evtracker.recv().await.unwrap();
+            if let EventType::WebxdcRealtimeData { data, .. } = event.typ {
+                if data == "alice -> bob".as_bytes() {
+                    break;
+                } else {
+                    panic!(
+                        "Unexpected status update: {}",
+                        String::from_utf8_lossy(&data)
+                    );
+                }
+            }
+        }
+        // Bob sends ephemeral message
+        bob_iroh
+            .send_webxdc_realtime_data(bob, bob_webdxc.id, "bob -> alice".as_bytes().to_vec())
+            .await
+            .unwrap();
+
+        loop {
+            let event = alice.evtracker.recv().await.unwrap();
+            if let EventType::WebxdcRealtimeData { data, .. } = event.typ {
+                if data == "bob -> alice".as_bytes() {
+                    break;
+                } else {
+                    panic!(
+                        "Unexpected status update: {}",
+                        String::from_utf8_lossy(&data)
+                    );
+                }
+            }
+        }
+
+        // Alice adds bob to gossip peers.
+        let members = get_iroh_gossip_peers(alice, alice_webxdc.id)
+            .await
+            .unwrap()
+            .into_iter()
+            .map(|addr| addr.node_id)
+            .collect::<Vec<_>>();
+
+        assert_eq!(
+            members,
+            vec![bob_iroh.get_node_addr().await.unwrap().node_id]
+        );
+
+        bob_iroh
+            .send_webxdc_realtime_data(bob, bob_webdxc.id, "bob -> alice 2".as_bytes().to_vec())
+            .await
+            .unwrap();
+
+        loop {
+            let event = alice.evtracker.recv().await.unwrap();
+            if let EventType::WebxdcRealtimeData { data, .. } = event.typ {
+                if data == "bob -> alice 2".as_bytes() {
+                    break;
+                } else {
+                    panic!(
+                        "Unexpected status update: {}",
+                        String::from_utf8_lossy(&data)
+                    );
+                }
+            }
+        }
+    }
+
+    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+    async fn test_can_reconnect() {
+        let mut tcm = TestContextManager::new();
+        let alice = &mut tcm.alice().await;
+        let bob = &mut tcm.bob().await;
+
+        // Alice sends webxdc to bob
+        let alice_chat = alice.create_chat(bob).await;
+        let mut instance = Message::new(Viewtype::File);
+        instance
+            .set_file_from_bytes(
+                alice,
+                "minimal.xdc",
+                include_bytes!("../test-data/webxdc/minimal.xdc"),
+                None,
+            )
+            .await
+            .unwrap();
+
+        send_msg(alice, alice_chat.id, &mut instance).await.unwrap();
+        let alice_webxdc = alice.get_last_msg().await;
+        assert_eq!(alice_webxdc.get_viewtype(), Viewtype::Webxdc);
+
+        let webxdc = alice.pop_sent_msg().await;
+        let bob_webdxc = bob.recv_msg(&webxdc).await;
+        assert_eq!(bob_webdxc.get_viewtype(), Viewtype::Webxdc);
+
+        bob_webdxc.chat_id.accept(bob).await.unwrap();
+
+        // Alice advertises herself.
+        send_webxdc_realtime_advertisement(alice, alice_webxdc.id)
+            .await
+            .unwrap();
+
+        bob.recv_msg_trash(&alice.pop_sent_msg().await).await;
+        let bob_iroh = bob.get_or_try_init_peer_channel().await.unwrap();
+
+        // Bob adds alice to gossip peers.
+        let members = get_iroh_gossip_peers(bob, bob_webdxc.id)
+            .await
+            .unwrap()
+            .into_iter()
+            .map(|addr| addr.node_id)
+            .collect::<Vec<_>>();
+
+        let alice_iroh = alice.get_or_try_init_peer_channel().await.unwrap();
+        assert_eq!(
+            members,
+            vec![alice_iroh.get_node_addr().await.unwrap().node_id]
+        );
+
+        bob_iroh
+            .join_and_subscribe_gossip(bob, bob_webdxc.id)
+            .await
+            .unwrap()
+            .unwrap()
+            .await
+            .unwrap();
+
+        // Alice sends ephemeral message
+        alice_iroh
+            .send_webxdc_realtime_data(alice, alice_webxdc.id, "alice -> bob".as_bytes().to_vec())
+            .await
+            .unwrap();
+
+        loop {
+            let event = bob.evtracker.recv().await.unwrap();
+            if let EventType::WebxdcRealtimeData { data, .. } = event.typ {
+                if data == "alice -> bob".as_bytes() {
+                    break;
+                } else {
+                    panic!(
+                        "Unexpected status update: {}",
+                        String::from_utf8_lossy(&data)
+                    );
+                }
+            }
+        }
+
+        // TODO: check that seq number is persisted
+        leave_webxdc_realtime(bob, bob_webdxc.id).await.unwrap();
+
+        bob_iroh
+            .join_and_subscribe_gossip(bob, bob_webdxc.id)
+            .await
+            .unwrap()
+            .unwrap()
+            .await
+            .unwrap();
+
+        bob_iroh
+            .send_webxdc_realtime_data(bob, bob_webdxc.id, "bob -> alice".as_bytes().to_vec())
+            .await
+            .unwrap();
+
+        loop {
+            let event = alice.evtracker.recv().await.unwrap();
+            if let EventType::WebxdcRealtimeData { data, .. } = event.typ {
+                if data == "bob -> alice".as_bytes() {
+                    break;
+                } else {
+                    panic!(
+                        "Unexpected status update: {}",
+                        String::from_utf8_lossy(&data)
+                    );
+                }
+            }
+        }
+
+        // channel is only used to remeber if an advertisement has been sent
+        // bob for example does not change the channels because he never sends an
+        // advertisement
+        assert_eq!(
+            alice.iroh.get().unwrap().iroh_channels.read().await.len(),
+            1
+        );
+        leave_webxdc_realtime(alice, alice_webxdc.id).await.unwrap();
+        let topic = get_iroh_topic_for_msg(alice, alice_webxdc.id)
+            .await
+            .unwrap();
+        assert!(if let Some(state) = alice
+            .iroh
+            .get()
+            .unwrap()
+            .iroh_channels
+            .read()
+            .await
+            .get(&topic)
+        {
+            state.subscribe_loop.is_none()
+        } else {
+            false
+        });
+    }
+}