fix: Use SystemTime instead of Instant everywhere

If a time value doesn't need to be sent to another host, saved to the db or otherwise used across
program restarts, a monotonically nondecreasing clock (`Instant`) should be used. But as `Instant`
may use `libc::clock_gettime(CLOCK_MONOTONIC)`, e.g. on Android, and does not advance while being in
deep sleep mode, get rid of `Instant` in favor of using `SystemTime`, but add `tools::Time` as an
alias for it with the appropriate comment so that it's clear why `Instant` isn't used in those
places and to protect from unwanted usages of `Instant` in the future. Also this can help to switch
to another clock impl if we find any.

src/constants.rs

@@ -217,7 +217,7 @@ pub(crate) const DC_FOLDERS_CONFIGURED_VERSION: i32 = 4;
 pub(crate) const DEFAULT_MAX_SMTP_RCPT_TO: usize = 50;
 
 /// How far the last quota check needs to be in the past to be checked by the background function (in seconds).
-pub(crate) const DC_BACKGROUND_FETCH_QUOTA_CHECK_RATELIMIT: i64 = 12 * 60 * 60; // 12 hours
+pub(crate) const DC_BACKGROUND_FETCH_QUOTA_CHECK_RATELIMIT: u64 = 12 * 60 * 60; // 12 hours
 
 #[cfg(test)]
 mod tests {

src/context.rs

@@ -6,7 +6,7 @@ use std::ops::Deref;
 use std::path::{Path, PathBuf};
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::Arc;
-use std::time::{Duration, Instant, SystemTime};
+use std::time::Duration;
 
 use anyhow::{bail, ensure, Context as _, Result};
 use async_channel::{self as channel, Receiver, Sender};
@@ -33,7 +33,7 @@ use crate::scheduler::{convert_folder_meaning, SchedulerState};
 use crate::sql::Sql;
 use crate::stock_str::StockStrings;
 use crate::timesmearing::SmearedTimestamp;
-use crate::tools::{create_id, duration_to_str, time};
+use crate::tools::{self, create_id, duration_to_str, time, time_elapsed};
 
 /// Builder for the [`Context`].
 ///
@@ -233,7 +233,7 @@ pub struct InnerContext {
     /// IMAP METADATA.
     pub(crate) metadata: RwLock<Option<ServerMetadata>>,
 
-    pub(crate) last_full_folder_scan: Mutex<Option<Instant>>,
+    pub(crate) last_full_folder_scan: Mutex<Option<tools::Time>>,
 
     /// ID for this `Context` in the current process.
     ///
@@ -241,7 +241,7 @@ pub struct InnerContext {
     /// be identified by this ID.
     pub(crate) id: u32,
 
-    creation_time: SystemTime,
+    creation_time: tools::Time,
 
     /// The text of the last error logged and emitted as an event.
     /// If the ui wants to display an error after a failure,
@@ -262,7 +262,7 @@ enum RunningState {
     Running { cancel_sender: Sender<()> },
 
     /// Cancel signal has been sent, waiting for ongoing process to be freed.
-    ShallStop { request: Instant },
+    ShallStop { request: tools::Time },
 
     /// There is no ongoing process, a new one can be allocated.
     Stopped,
@@ -394,7 +394,7 @@ impl Context {
             new_msgs_notify,
             server_id: RwLock::new(None),
             metadata: RwLock::new(None),
-            creation_time: std::time::SystemTime::now(),
+            creation_time: tools::Time::now(),
             last_full_folder_scan: Mutex::new(None),
             last_error: std::sync::RwLock::new("".to_string()),
             debug_logging: std::sync::RwLock::new(None),
@@ -454,7 +454,7 @@ impl Context {
         }
 
         let address = self.get_primary_self_addr().await?;
-        let time_start = std::time::SystemTime::now();
+        let time_start = tools::Time::now();
         info!(self, "background_fetch started fetching {address}");
 
         let _pause_guard = self.scheduler.pause(self.clone()).await?;
@@ -476,7 +476,10 @@ impl Context {
             let quota = self.quota.read().await;
             quota
                 .as_ref()
-                .filter(|quota| quota.modified + DC_BACKGROUND_FETCH_QUOTA_CHECK_RATELIMIT > time())
+                .filter(|quota| {
+                    time_elapsed(&quota.modified)
+                        > Duration::from_secs(DC_BACKGROUND_FETCH_QUOTA_CHECK_RATELIMIT)
+                })
                 .is_none()
         };
 
@@ -489,7 +492,7 @@ impl Context {
         info!(
             self,
             "background_fetch done for {address} took {:?}",
-            time_start.elapsed().unwrap_or_default()
+            time_elapsed(&time_start),
         );
 
         Ok(())
@@ -591,7 +594,7 @@ impl Context {
     pub(crate) async fn free_ongoing(&self) {
         let mut s = self.running_state.write().await;
         if let RunningState::ShallStop { request } = *s {
-            info!(self, "Ongoing stopped in {:?}", request.elapsed());
+            info!(self, "Ongoing stopped in {:?}", time_elapsed(&request));
         }
         *s = RunningState::Stopped;
     }
@@ -606,7 +609,7 @@ impl Context {
                 }
                 info!(self, "Signaling the ongoing process to stop ASAP.",);
                 *s = RunningState::ShallStop {
-                    request: Instant::now(),
+                    request: tools::Time::now(),
                 };
             }
             RunningState::ShallStop { .. } | RunningState::Stopped => {
@@ -867,8 +870,8 @@ impl Context {
                 .to_string(),
         );
 
-        let elapsed = self.creation_time.elapsed();
+        let elapsed = time_elapsed(&self.creation_time);
-        res.insert("uptime", duration_to_str(elapsed.unwrap_or_default()));
+        res.insert("uptime", duration_to_str(elapsed));
 
         Ok(res)
     }
@@ -1214,7 +1217,7 @@ pub fn get_version_str() -> &'static str {
 
 #[cfg(test)]
 mod tests {
-    use std::time::Duration;
+    use std::time::{Duration, SystemTime};
 
     use anyhow::Context as _;
     use strum::IntoEnumIterator;

src/imap/idle.rs

@@ -1,4 +1,4 @@
-use std::time::{Duration, SystemTime};
+use std::time::Duration;
 
 use anyhow::{bail, Context as _, Result};
 use async_channel::Receiver;
@@ -11,6 +11,7 @@ use crate::config::Config;
 use crate::context::Context;
 use crate::imap::{client::IMAP_TIMEOUT, FolderMeaning};
 use crate::log::LogExt;
+use crate::tools::{self, time_elapsed};
 
 /// Timeout after which IDLE is finished
 /// if there are no responses from the server.
@@ -106,7 +107,7 @@ impl Imap {
         // Idle using polling. This is also needed if we're not yet configured -
         // in this case, we're waiting for a configure job (and an interrupt).
 
-        let fake_idle_start_time = SystemTime::now();
+        let fake_idle_start_time = tools::Time::now();
 
         // Do not poll, just wait for an interrupt when no folder is passed in.
         let watch_folder = if let Some(watch_folder) = watch_folder {
@@ -196,11 +197,7 @@ impl Imap {
         info!(
             context,
             "IMAP-fake-IDLE done after {:.4}s",
-            SystemTime::now()
+            time_elapsed(&fake_idle_start_time).as_millis() as f64 / 1000.,
-                .duration_since(fake_idle_start_time)
-                .unwrap_or_default()
-                .as_millis() as f64
-                / 1000.,
         );
     }
 }

src/imap/scan_folders.rs

@@ -1,4 +1,4 @@
-use std::{collections::BTreeMap, time::Instant};
+use std::collections::BTreeMap;
 
 use anyhow::{Context as _, Result};
 use futures::TryStreamExt;
@@ -7,6 +7,7 @@ use super::{get_folder_meaning_by_attrs, get_folder_meaning_by_name};
 use crate::config::Config;
 use crate::imap::Imap;
 use crate::log::LogExt;
+use crate::tools::{self, time_elapsed};
 use crate::{context::Context, imap::FolderMeaning};
 
 impl Imap {
@@ -15,7 +16,7 @@ impl Imap {
         // First of all, debounce to once per minute:
         let mut last_scan = context.last_full_folder_scan.lock().await;
         if let Some(last_scan) = *last_scan {
-            let elapsed_secs = last_scan.elapsed().as_secs();
+            let elapsed_secs = time_elapsed(&last_scan).as_secs();
             let debounce_secs = context
                 .get_config_u64(Config::ScanAllFoldersDebounceSecs)
                 .await?;
@@ -93,7 +94,7 @@ impl Imap {
                 .await?;
         }
 
-        last_scan.replace(Instant::now());
+        last_scan.replace(tools::Time::now());
         Ok(true)
     }
 

src/key.rs

@@ -18,7 +18,7 @@ use crate::constants::KeyGenType;
 use crate::context::Context;
 use crate::log::LogExt;
 use crate::pgp::KeyPair;
-use crate::tools::EmailAddress;
+use crate::tools::{self, time_elapsed, EmailAddress};
 
 /// Convenience trait for working with keys.
 ///
@@ -204,7 +204,7 @@ async fn generate_keypair(context: &Context) -> Result<KeyPair> {
     match load_keypair(context, &addr).await? {
         Some(key_pair) => Ok(key_pair),
         None => {
-            let start = std::time::SystemTime::now();
+            let start = tools::Time::now();
             let keytype = KeyGenType::from_i32(context.get_config_int(Config::KeyGenType).await?)
                 .unwrap_or_default();
             info!(context, "Generating keypair with type {}", keytype);
@@ -216,7 +216,7 @@ async fn generate_keypair(context: &Context) -> Result<KeyPair> {
             info!(
                 context,
                 "Keypair generated in {:.3}s.",
-                start.elapsed().unwrap_or_default().as_secs()
+                time_elapsed(&start).as_secs(),
             );
             Ok(keypair)
         }

src/quota.rs

@@ -12,7 +12,7 @@ use crate::imap::scan_folders::get_watched_folders;
 use crate::imap::session::Session as ImapSession;
 use crate::imap::Imap;
 use crate::message::{Message, Viewtype};
-use crate::tools::time;
+use crate::tools;
 use crate::{stock_str, EventType};
 
 /// warn about a nearly full mailbox after this usage percentage is reached.
@@ -40,8 +40,8 @@ pub struct QuotaInfo {
     /// set to `Ok()` for valid quota information.
     pub(crate) recent: Result<BTreeMap<String, Vec<QuotaResource>>>,
 
-    /// Timestamp when structure was modified.
+    /// When the structure was modified.
-    pub(crate) modified: i64,
+    pub(crate) modified: tools::Time,
 }
 
 async fn get_unique_quota_roots_and_usage(
@@ -151,7 +151,7 @@ impl Context {
 
         *self.quota.write().await = Some(QuotaInfo {
             recent: quota,
-            modified: time(),
+            modified: tools::Time::now(),
         });
 
         self.emit_event(EventType::ConnectivityChanged);

src/scheduler.rs

@@ -2,6 +2,7 @@ use std::cmp;
 use std::iter::{self, once};
 use std::num::NonZeroUsize;
 use std::sync::atomic::Ordering;
+use std::time::Duration;
 
 use anyhow::{bail, Context as _, Error, Result};
 use async_channel::{self as channel, Receiver, Sender};
@@ -24,7 +25,7 @@ use crate::log::LogExt;
 use crate::message::MsgId;
 use crate::smtp::{send_smtp_messages, Smtp};
 use crate::sql;
-use crate::tools::{duration_to_str, maybe_add_time_based_warnings, time};
+use crate::tools::{self, duration_to_str, maybe_add_time_based_warnings, time, time_elapsed};
 
 pub(crate) mod connectivity;
 
@@ -398,7 +399,7 @@ async fn inbox_loop(
                     let quota = ctx.quota.read().await;
                     quota
                         .as_ref()
-                        .filter(|quota| quota.modified + 60 > time())
+                        .filter(|quota| time_elapsed(&quota.modified) > Duration::from_secs(60))
                         .is_none()
                 };
 
@@ -785,7 +786,7 @@ async fn smtp_loop(
             // again, we increase the timeout exponentially, in order not to do lots of
             // unnecessary retries.
             if let Some(t) = timeout {
-                let now = tokio::time::Instant::now();
+                let now = tools::Time::now();
                 info!(
                     ctx,
                     "smtp has messages to retry, planning to retry {} seconds later", t,
@@ -796,7 +797,7 @@ async fn smtp_loop(
                 })
                 .await
                 .unwrap_or_default();
-                let slept = (tokio::time::Instant::now() - now).as_secs();
+                let slept = time_elapsed(&now).as_secs();
                 timeout = Some(cmp::max(
                     t,
                     slept.saturating_add(rand::thread_rng().gen_range((slept / 2)..=slept)),

src/smtp.rs

@@ -2,7 +2,7 @@
 
 pub mod send;
 
-use std::time::{Duration, SystemTime};
+use std::time::Duration;
 
 use anyhow::{bail, format_err, Context as _, Error, Result};
 use async_smtp::response::{Category, Code, Detail};
@@ -28,6 +28,7 @@ use crate::scheduler::connectivity::ConnectivityStore;
 use crate::socks::Socks5Config;
 use crate::sql;
 use crate::stock_str::unencrypted_email;
+use crate::tools::{self, time_elapsed};
 
 /// SMTP connection, write and read timeout.
 const SMTP_TIMEOUT: Duration = Duration::from_secs(60);
@@ -43,7 +44,7 @@ pub(crate) struct Smtp {
     /// Timestamp of last successful send/receive network interaction
     /// (eg connect or send succeeded). On initialization and disconnect
     /// it is set to None.
-    last_success: Option<SystemTime>,
+    last_success: Option<tools::Time>,
 
     pub(crate) connectivity: ConnectivityStore,
 
@@ -72,11 +73,7 @@ impl Smtp {
     /// have been successfully used the last 60 seconds
     pub fn has_maybe_stale_connection(&self) -> bool {
         if let Some(last_success) = self.last_success {
-            SystemTime::now()
+            time_elapsed(&last_success).as_secs() > 60
-                .duration_since(last_success)
-                .unwrap_or_default()
-                .as_secs()
-                > 60
         } else {
             false
         }
@@ -336,7 +333,7 @@ impl Smtp {
         }
 
         self.transport = Some(transport);
-        self.last_success = Some(SystemTime::now());
+        self.last_success = Some(tools::Time::now());
 
         context.emit_event(EventType::SmtpConnected(format!(
             "SMTP-LOGIN as {} ok",

src/smtp/send.rs

@@ -6,6 +6,7 @@ use super::Smtp;
 use crate::config::Config;
 use crate::context::Context;
 use crate::events::EventType;
+use crate::tools;
 
 pub type Result<T> = std::result::Result<T, Error>;
 
@@ -55,7 +56,7 @@ impl Smtp {
                 format!("Message len={message_len_bytes} was SMTP-sent to {recipients_display}");
             info!(context, "{info_msg}.");
             context.emit_event(EventType::SmtpMessageSent(info_msg));
-            self.last_success = Some(std::time::SystemTime::now());
+            self.last_success = Some(tools::Time::now());
         } else {
             warn!(
                 context,

src/tools.rs

@@ -9,6 +9,13 @@ use std::io::{Cursor, Write};
 use std::mem;
 use std::path::{Path, PathBuf};
 use std::str::from_utf8;
+// If a time value doesn't need to be sent to another host, saved to the db or otherwise used across
+// program restarts, a monotonically nondecreasing clock (`Instant`) should be used. But as
+// `Instant` may use `libc::clock_gettime(CLOCK_MONOTONIC)`, e.g. on Android, and does not advance
+// while being in deep sleep mode, we use `SystemTime` instead, but add an alias for it to document
+// why `Instant` isn't used in those places. Also this can help to switch to another clock impl if
+// we find any.
+pub use std::time::SystemTime as Time;
 use std::time::{Duration, SystemTime};
 
 use anyhow::{bail, Context as _, Result};
@@ -482,6 +489,10 @@ pub(crate) fn time() -> i64 {
         .as_secs() as i64
 }
 
+pub(crate) fn time_elapsed(time: &Time) -> Duration {
+    time.elapsed().unwrap_or_default()
+}
+
 /// Struct containing all mailto information
 #[derive(Debug, Default, Eq, PartialEq)]
 pub struct MailTo {