imap: disable read timeout during IDLE

Otherwise IDLE restarts every 30 seconds.

CHANGELOG.md

@@ -30,6 +30,7 @@
 - python: do not pass NULL to ffi.gc if the context can't be created #3818
 - Add read/write timeouts to IMAP sockets #3820
 - Add connection timeout to IMAP sockets #3828
+- Disable read timeout during IMAP IDLE #3826
 
 
 ## 1.102.0

Cargo.lock

@@ -123,7 +123,7 @@ dependencies = [
 [[package]]
 name = "async-imap"
 version = "0.6.0"
-source = "git+https://github.com/async-email/async-imap?branch=master#8755b666fcd8991ed4d09864b67aa88a1eb6934f"
+source = "git+https://github.com/async-email/async-imap?branch=master#85ff7a3d9d71a3715354fabf2fc1a8d047b5710e"
 dependencies = [
  "async-channel",
  "async-native-tls",

src/imap/client.rs

@@ -20,7 +20,7 @@ use crate::login_param::{build_tls, Socks5Config};
 use super::session::SessionStream;
 
 /// IMAP write and read timeout in seconds.
-const IMAP_TIMEOUT: Duration = Duration::from_secs(30);
+pub(crate) const IMAP_TIMEOUT: Duration = Duration::from_secs(30);
 
 #[derive(Debug)]
 pub(crate) struct Client {

src/imap/idle.rs

@@ -7,8 +7,11 @@ use futures_lite::FutureExt;
 use std::time::{Duration, SystemTime};
 
 use super::session::Session;
+use crate::imap::client::IMAP_TIMEOUT;
 use crate::{context::Context, scheduler::InterruptInfo};
 
+const IDLE_TIMEOUT: Duration = Duration::from_secs(23 * 60);
+
 impl Session {
     pub async fn idle(
         mut self,
@@ -22,7 +25,6 @@ impl Session {
             bail!("IMAP server does not have IDLE capability");
         }
 
-        let timeout = Duration::from_secs(23 * 60);
         let mut info = Default::default();
 
         self.select_folder(context, watch_folder.as_deref()).await?;
@@ -41,7 +43,12 @@ impl Session {
             bail!("IMAP IDLE protocol failed to init/complete: {}", err);
         }
 
-        let (idle_wait, interrupt) = handle.wait_with_timeout(timeout);
+        // At this point IDLE command was sent and we received a "+ idling" response. We will now
+        // read from the stream without getting any data for up to `IDLE_TIMEOUT`. If we don't
+        // disable read timeout, we would get a timeout after `IMAP_TIMEOUT`, which is a lot
+        // shorter than `IDLE_TIMEOUT`.
+        handle.as_mut().set_read_timeout(None);
+        let (idle_wait, interrupt) = handle.wait_with_timeout(IDLE_TIMEOUT);
 
         enum Event {
             IdleResponse(IdleResponse),
@@ -90,10 +97,11 @@ impl Session {
             }
         }
 
-        let session = tokio::time::timeout(Duration::from_secs(15), handle.done())
+        let mut session = tokio::time::timeout(Duration::from_secs(15), handle.done())
             .await
             .with_context(|| format!("{}: IMAP IDLE protocol timed out", folder_name))?
             .with_context(|| format!("{}: IMAP IDLE failed", folder_name))?;
+        session.as_mut().set_read_timeout(Some(IMAP_TIMEOUT));
         self.inner = session;
 
         Ok((self, info))

src/imap/session.rs

@@ -1,5 +1,6 @@
 use std::ops::{Deref, DerefMut};
 use std::pin::Pin;
+use std::time::Duration;
 
 use async_imap::types::Mailbox;
 use async_imap::Session as ImapSession;
@@ -28,14 +29,31 @@ pub(crate) struct Session {
 pub(crate) trait SessionStream:
     tokio::io::AsyncRead + tokio::io::AsyncWrite + Unpin + Send + Sync + std::fmt::Debug
 {
+    /// Change the read timeout on the session stream.
+    fn set_read_timeout(&mut self, timeout: Option<Duration>);
 }
 
-impl SessionStream for TlsStream<Box<dyn SessionStream>> {}
-impl SessionStream for TlsStream<Pin<Box<TimeoutStream<TcpStream>>>> {}
-impl SessionStream for TlsStream<TcpStream> {}
-impl SessionStream for TcpStream {}
-impl SessionStream for Pin<Box<TimeoutStream<TcpStream>>> {}
-impl SessionStream for Socks5Stream<TcpStream> {}
+impl SessionStream for TlsStream<Box<dyn SessionStream>> {
+    fn set_read_timeout(&mut self, timeout: Option<Duration>) {
+        self.get_mut().set_read_timeout(timeout);
+    }
+}
+impl SessionStream for TlsStream<Pin<Box<TimeoutStream<TcpStream>>>> {
+    fn set_read_timeout(&mut self, timeout: Option<Duration>) {
+        self.get_mut().set_read_timeout(timeout);
+    }
+}
+impl SessionStream for Pin<Box<TimeoutStream<TcpStream>>> {
+    fn set_read_timeout(&mut self, timeout: Option<Duration>) {
+        self.as_mut().set_read_timeout_pinned(timeout);
+    }
+}
+impl SessionStream for Socks5Stream<TcpStream> {
+    fn set_read_timeout(&mut self, _timeout: Option<Duration>) {
+        // FIXME: build SOCKS streams on top of TimeoutStream, not directly TcpStream,
+        // so we can set a read timeout for them.
+    }
+}
 
 impl Deref for Session {
     type Target = ImapSession<Box<dyn SessionStream>>;