The switch now reaches the running server

The join: the policy decides, features owns the listener objects,
ListenerControl owns the running sockets, and only Server has both.

Server::set_protocol_policy is what a click performs. It applies the locks
to what was asked before storing anything (LP-21), so what is recorded is
what the server allows. Closing removes each listener object and then stops
its socket; opening puts the object back and then spawns it. The order is
the point in both directions -- a socket stopped while its object remains
returns on the next restart, and a socket spawned before its object exists
has nothing to come back to.

saved_listeners is carried over from the stored policy rather than taken
from the request. A client never sets it, and a /set that omitted it would
otherwise lose the listeners still waiting to come back.

Putting a listener back has to bind a fresh socket, so it re-parses from
the registry -- the objects are already back by then -- rather than trying
to revive the saved one. Only main knows which session manager a protocol
wants, so it leaves a spawner behind at startup and spawn_listener is now
shared between that and the initial spawn. Without a spawner a restored
listener is reported as pending a restart rather than promised, which is
what the test servers will see.

A listener that cannot be put back does not stop the others and stays
saved for another try (LP-5).

Still nothing an operator can reach: no JMAP method calls this yet, and no
sign-in is refused. What it does do is close and reopen a port on a
running server, which is the part that did not exist this morning.

crates/common/src/network/control.rs

@@ -23,11 +23,18 @@
 //! process stops answering; anything that still routes the port is the
 //! operator's to reconcile, and is deliberately left alone.
 
-use crate::config::server::ServerProtocol;
+use crate::config::server::{Listener, ServerProtocol};
+use crate::network::TcpAcceptor;
 use ahash::AHashMap;
 use parking_lot::RwLock;
+use std::sync::OnceLock;
 use tokio::sync::watch;
 
+/// How a listener is spawned. Only `main` knows how to build the session
+/// manager for a protocol, so it leaves this behind at startup and the policy
+/// uses it to put a listener back without a restart (LP-5).
+pub type SpawnListener = Box<dyn Fn(Listener, TcpAcceptor, watch::Receiver<bool>) + Send + Sync>;
+
 /// A listener that is currently accepting, and the switch that stops it.
 struct Running {
     protocol: ServerProtocol,
@@ -47,6 +54,7 @@ pub struct ListenerInfo {
 #[derive(Default)]
 pub struct ListenerControl {
     running: RwLock<AHashMap<String, Running>>,
+    spawner: OnceLock<SpawnListener>,
 }
 
 impl ListenerControl {
@@ -70,6 +78,33 @@ impl ListenerControl {
         shutdown_rx
     }
 
+    /// Remembers how to spawn a listener, once, at startup. Later calls are
+    /// ignored, so nothing can swap the spawner out from under a running
+    /// server.
+    pub fn set_spawner(&self, spawner: SpawnListener) {
+        let _ = self.spawner.set(spawner);
+    }
+
+    /// Whether a spawner has been left behind. Without one, a listener can be
+    /// stopped but not started, and the caller has to say so rather than
+    /// promise a port that will not open until a restart.
+    pub fn can_spawn(&self) -> bool {
+        self.spawner.get().is_some()
+    }
+
+    /// Starts a listener and registers it, so it can be stopped again.
+    /// Returns false when no spawner was left behind.
+    pub fn spawn(&self, listener: Listener, acceptor: TcpAcceptor) -> bool {
+        let Some(spawner) = self.spawner.get() else {
+            return false;
+        };
+
+        let ports = listener.listeners.iter().map(|l| l.addr.port()).collect();
+        let shutdown_rx = self.register(listener.id.clone(), listener.protocol, ports);
+        spawner(listener, acceptor, shutdown_rx);
+        true
+    }
+
     /// Stops one listener by id. Returns what was stopped, or `None` when no
     /// listener of that id is running.
     pub fn stop(&self, id: &str) -> Option<ListenerInfo> {

crates/common/src/network/legacy.rs

@@ -0,0 +1,188 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Coffey Labs
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+//! Turning the legacy-protocols switch, and making it true of the running
+//! server (legacy-protocols spec, LP-1, LP-2 and LP-5).
+//!
+//! Two halves meet here. `inbuxa_features::security` decides what the policy
+//! means and owns the listener **objects**; [`ListenerControl`] owns the
+//! running **sockets**. Neither can do the job alone, and only `Server` has
+//! both, so the join lives here.
+//!
+//! Order matters in both directions. Closing removes the object first and then
+//! stops the socket: a socket stopped before its object is gone would come
+//! back on the next restart. Opening puts the object back first and then
+//! spawns, for the same reason in reverse.
+//!
+//! Nothing here touches the host's firewall, NAT port-forwards or any proxy
+//! (LP-20). The server stops answering; what still routes the port is the
+//! operator's to reconcile.
+
+use crate::{Server, config::server::Listeners, network::TcpAcceptor};
+use inbuxa_features::security::{
+    listeners,
+    protocol_policy::{self, ProtocolPolicy, SavedListener},
+};
+use store::registry::bootstrap::Bootstrap;
+
+/// What turning the switch actually did.
+#[derive(Debug, Default)]
+pub struct PolicyChange {
+    /// Listeners removed and stopped (LP-1).
+    pub closed: Vec<SavedListener>,
+    /// Listeners put back and started again (LP-5).
+    pub reopened: Vec<SavedListener>,
+    /// Listeners that could not be put back, with the reason. Each stays
+    /// saved for another try (LP-5).
+    pub failed: Vec<(SavedListener, String)>,
+    /// Properties the locks overruled (LP-21).
+    pub overruled: Vec<&'static str>,
+    /// Listeners whose object is right but whose socket needs a restart,
+    /// because no spawner was left behind. Empty on a normally booted server.
+    pub pending_restart: Vec<String>,
+}
+
+impl PolicyChange {
+    /// Whether anything at all happened, for the caller deciding to emit
+    /// `security.legacy-protocols-changed` (LP-8).
+    pub fn is_empty(&self) -> bool {
+        self.closed.is_empty()
+            && self.reopened.is_empty()
+            && self.failed.is_empty()
+            && self.overruled.is_empty()
+    }
+}
+
+impl Server {
+    /// The policy in force.
+    pub async fn protocol_policy(&self) -> trc::Result<ProtocolPolicy> {
+        protocol_policy::get(&self.core.storage.data).await
+    }
+
+    /// Turns the switch, and makes it true of the running server.
+    ///
+    /// `requested` is what the client asked for; the locks are applied to it
+    /// first (LP-21), so what gets stored is what the server allows, not what
+    /// was asked. Returns what actually happened, for the response and the
+    /// event.
+    pub async fn set_protocol_policy(
+        &self,
+        requested: ProtocolPolicy,
+        changed_by: Option<String>,
+    ) -> trc::Result<PolicyChange> {
+        let mut policy = requested;
+        let mut change = PolicyChange {
+            overruled: policy.apply_locks(),
+            ..Default::default()
+        };
+
+        // Carry forward what earlier changes saved: the client never sets
+        // this, and a /set that omitted it must not lose the listeners still
+        // waiting to come back.
+        let previous = self.protocol_policy().await?;
+        policy.saved_listeners = previous.saved_listeners;
+        policy.changed_at = Some(store::write::now() * 1000);
+        policy.changed_by = changed_by;
+
+        if policy.legacy_protocols.is_disabled() {
+            self.close_legacy_listeners(&mut policy, &mut change).await?;
+        } else {
+            self.reopen_legacy_listeners(&mut policy, &mut change)
+                .await?;
+        }
+
+        protocol_policy::set(&self.core.storage.data, &policy).await?;
+
+        Ok(change)
+    }
+
+    /// Removes the listener objects the policy closes, then stops their
+    /// sockets (LP-1, LP-2).
+    async fn close_legacy_listeners(
+        &self,
+        policy: &mut ProtocolPolicy,
+        change: &mut PolicyChange,
+    ) -> trc::Result<()> {
+        let removed = listeners::close(self.registry(), policy).await?;
+
+        for saved in &removed {
+            // The runtime registry is keyed by the listener's name, which is
+            // what `close` returns as the saved listener's id.
+            self.inner.data.listener_control.stop(&saved.id);
+        }
+
+        policy.saved_listeners.extend(removed.iter().cloned());
+        change.closed = removed;
+
+        Ok(())
+    }
+
+    /// Puts back every saved listener and starts it again (LP-5).
+    async fn reopen_legacy_listeners(
+        &self,
+        policy: &mut ProtocolPolicy,
+        change: &mut PolicyChange,
+    ) -> trc::Result<()> {
+        if policy.saved_listeners.is_empty() {
+            return Ok(());
+        }
+
+        let saved = std::mem::take(&mut policy.saved_listeners);
+        let (restored, failed) = listeners::reopen(self.registry(), &saved).await?;
+
+        // A listener that could not be put back stays saved for another try.
+        policy.saved_listeners = failed.iter().map(|(listener, _)| listener.clone()).collect();
+        change.failed = failed;
+
+        if !restored.is_empty() {
+            change.pending_restart = self.spawn_restored_listeners(&restored).await?;
+        }
+        change.reopened = restored;
+
+        Ok(())
+    }
+
+    /// Binds and spawns the listeners just put back, so a port opens without a
+    /// restart. Returns the names that still need one.
+    async fn spawn_restored_listeners(&self, restored: &[SavedListener]) -> trc::Result<Vec<String>> {
+        let control = &self.inner.data.listener_control;
+        if !control.can_spawn() {
+            return Ok(restored.iter().map(|listener| listener.id.clone()).collect());
+        }
+
+        // Re-parse from the registry rather than from the saved object: the
+        // socket has to be created and bound afresh, and the parser is what
+        // knows how. The objects are already back, so this sees them.
+        let mut bootstrap = Bootstrap::new(self.registry().clone()).await;
+        let mut parsed = Listeners::parse(&mut bootstrap).await;
+        parsed
+            .parse_tcp_acceptors(&mut bootstrap, self.inner.clone())
+            .await;
+
+        let wanted: Vec<&str> = restored.iter().map(|l| l.id.as_str()).collect();
+        let mut spawned = Vec::new();
+
+        let mut acceptors = std::mem::take(&mut parsed.tcp_acceptors);
+        for listener in parsed.servers {
+            if !wanted.contains(&listener.id.as_str()) || control.is_running(&listener.id) {
+                continue;
+            }
+            let acceptor = acceptors
+                .remove(&listener.id)
+                .unwrap_or(TcpAcceptor::Plain);
+            let id = listener.id.clone();
+            if control.spawn(listener, acceptor) {
+                spawned.push(id);
+            }
+        }
+
+        Ok(restored
+            .iter()
+            .map(|listener| listener.id.clone())
+            .filter(|id| !spawned.contains(id))
+            .collect())
+    }
+}

crates/common/src/network/mod.rs

@@ -36,6 +36,7 @@ pub mod autoconfig;
 pub mod control;
 pub mod dkim;
 pub mod dns;
+pub mod legacy;
 pub mod limiter;
 pub mod listen;
 pub mod mta;

crates/main/src/main.rs

@@ -9,14 +9,21 @@
 #![warn(clippy::cast_possible_wrap)]
 #![warn(clippy::cast_sign_loss)]
 
-use common::{BuildServer, config::server::ServerProtocol, manager::boot::BootManager};
+use common::{
+    BuildServer, Inner,
+    config::server::{Listener, ServerProtocol},
+    manager::boot::BootManager,
+    network::TcpAcceptor,
+};
 use http::HttpSessionManager;
 use imap::core::ImapSessionManager;
 use managesieve::core::ManageSieveSessionManager;
 use pop3::Pop3SessionManager;
 use services::{StartServices, broadcast::subscriber::spawn_broadcast_subscriber};
 use smtp::{StartQueueManager, core::SmtpSessionManager};
+use std::sync::Arc;
 use std::time::Duration;
+use tokio::sync::watch;
 use trc::Collector;
 use utils::wait_for_shutdown;
 
@@ -75,43 +82,24 @@ async fn main() -> std::io::Result<()> {
     // rest accepting (legacy-protocols LP-2). The registry lives in `Data` and
     // so outlives the listeners, which it must: it owns the sending ends.
     let listener_control = &init.inner.data.listener_control;
+    let spawn_inner = init.inner.clone();
     let (shutdown_tx, shutdown_rx) =
         init.servers
             .spawn_with_control(listener_control, |server, acceptor, shutdown_rx| {
-                match &server.protocol {
+                spawn_listener(&spawn_inner, server, acceptor, shutdown_rx);
-                    ServerProtocol::Smtp | ServerProtocol::Lmtp => server.spawn(
-                        SmtpSessionManager::new(init.inner.clone()),
-                        init.inner.clone(),
-                        acceptor,
-                        shutdown_rx,
-                    ),
-                    ServerProtocol::Http => server.spawn(
-                        HttpSessionManager::new(init.inner.clone()),
-                        init.inner.clone(),
-                        acceptor,
-                        shutdown_rx,
-                    ),
-                    ServerProtocol::Imap => server.spawn(
-                        ImapSessionManager::new(init.inner.clone()),
-                        init.inner.clone(),
-                        acceptor,
-                        shutdown_rx,
-                    ),
-                    ServerProtocol::Pop3 => server.spawn(
-                        Pop3SessionManager::new(init.inner.clone()),
-                        init.inner.clone(),
-                        acceptor,
-                        shutdown_rx,
-                    ),
-                    ServerProtocol::ManageSieve => server.spawn(
-                        ManageSieveSessionManager::new(init.inner.clone()),
-                        init.inner.clone(),
-                        acceptor,
-                        shutdown_rx,
-                    ),
-                };
             });
 
+    // Leave behind how to spawn a listener, so putting one back opens its port
+    // without a restart (LP-5). Only this file knows the session manager for a
+    // protocol, so only this file can say.
+    let spawn_inner = init.inner.clone();
+    init.inner
+        .data
+        .listener_control
+        .set_spawner(Box::new(move |server, acceptor, shutdown_rx| {
+            spawn_listener(&spawn_inner, server, acceptor, shutdown_rx);
+        }));
+
     // Start broadcast subscriber
     let inner = init.inner.clone();
     spawn_broadcast_subscriber(init.inner, shutdown_rx);
@@ -132,3 +120,47 @@ async fn main() -> std::io::Result<()> {
 
     Ok(())
 }
+
+/// Starts one listener under the session manager its protocol calls for.
+///
+/// Used twice: once for every listener at startup, and again whenever the
+/// legacy-protocols switch puts a listener back (LP-5).
+fn spawn_listener(
+    inner: &Arc<Inner>,
+    server: Listener,
+    acceptor: TcpAcceptor,
+    shutdown_rx: watch::Receiver<bool>,
+) {
+    match &server.protocol {
+        ServerProtocol::Smtp | ServerProtocol::Lmtp => server.spawn(
+            SmtpSessionManager::new(inner.clone()),
+            inner.clone(),
+            acceptor,
+            shutdown_rx,
+        ),
+        ServerProtocol::Http => server.spawn(
+            HttpSessionManager::new(inner.clone()),
+            inner.clone(),
+            acceptor,
+            shutdown_rx,
+        ),
+        ServerProtocol::Imap => server.spawn(
+            ImapSessionManager::new(inner.clone()),
+            inner.clone(),
+            acceptor,
+            shutdown_rx,
+        ),
+        ServerProtocol::Pop3 => server.spawn(
+            Pop3SessionManager::new(inner.clone()),
+            inner.clone(),
+            acceptor,
+            shutdown_rx,
+        ),
+        ServerProtocol::ManageSieve => server.spawn(
+            ManageSieveSessionManager::new(inner.clone()),
+            inner.clone(),
+            acceptor,
+            shutdown_rx,
+        ),
+    }
+}