From f930bd6b96d917acfe08269210a580d77e74d51f Mon Sep 17 00:00:00 2001
From: Orne Brocaar <info@brocaar.com>
Date: Wed, 19 Jul 2023 11:27:55 +0100
Subject: [PATCH] Wait for first uplink for Class-C scheduling.

---
 chirpstack/src/downlink/data.rs     | 13 ++++++++++++-
 chirpstack/src/test/class_c_test.rs | 29 +++++++++++++++++++++++++++--
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/chirpstack/src/downlink/data.rs b/chirpstack/src/downlink/data.rs
index ee20126d..9f659c71 100644
--- a/chirpstack/src/downlink/data.rs
+++ b/chirpstack/src/downlink/data.rs
@@ -291,6 +291,7 @@ impl Data {
 
         ctx.select_downlink_gateway()?;
         if ctx._is_class_c() {
+            ctx.check_for_first_uplink()?;
             ctx.get_class_c_device_lock().await?;
             ctx.set_immediately()?;
             ctx.set_tx_info_for_rx2()?;
@@ -705,7 +706,7 @@ impl Data {
             // this is not an ACK, then DownlinkDataMIC will zero out ConfFCnt.
             phy.set_downlink_data_mic(
                 self.device_session.mac_version().from_proto(),
-                self.device_session.f_cnt_up - 1,
+                self.device_session.f_cnt_up.overflowing_sub(1).0,
                 &lrwn::AES128Key::from_slice(&self.device_session.s_nwk_s_int_key)?,
             )
             .context("Set downlink data MIC")?;
@@ -861,6 +862,16 @@ impl Data {
         Ok(())
     }
 
+    fn check_for_first_uplink(&self) -> Result<()> {
+        trace!("Checking if device has sent its first uplink already");
+
+        if self.device_session.f_cnt_up == 0 {
+            return Err(anyhow!("Device must send its first uplink first"));
+        }
+
+        Ok(())
+    }
+
     async fn get_class_c_device_lock(&self) -> Result<()> {
         trace!("Getting Class-C device lock");
         let conf = config::get();
diff --git a/chirpstack/src/test/class_c_test.rs b/chirpstack/src/test/class_c_test.rs
index 9a530d72..5a85f8b1 100644
--- a/chirpstack/src/test/class_c_test.rs
+++ b/chirpstack/src/test/class_c_test.rs
@@ -105,6 +105,31 @@ async fn test_downlink_scheduler() {
         ..Default::default()
     };
 
+    let ds_no_uplink = internal::DeviceSession {
+        f_cnt_up: 0,
+        ..ds.clone()
+    };
+
+    run_scheduler_test(&DownlinkTest {
+        name: "device has not yet sent an uplink".into(),
+        device_queue_items: vec![device_queue::DeviceQueueItem {
+            id: Uuid::nil(),
+            dev_eui: dev.dev_eui.clone(),
+            f_port: 10,
+            data: vec![1, 2, 3],
+            ..Default::default()
+        }],
+        device_session: Some(ds_no_uplink.clone()),
+        device_gateway_rx_info: Some(device_gateway_rx_info.clone()),
+        assert: vec![assert::no_downlink_frame()],
+    })
+    .await;
+
+    // remove the schedule run after
+    device::set_scheduler_run_after(&dev.dev_eui.clone(), None)
+        .await
+        .unwrap();
+
     run_scheduler_test(&DownlinkTest {
         name: "unconfirmed data".into(),
         device_queue_items: vec![device_queue::DeviceQueueItem {
@@ -172,7 +197,7 @@ async fn test_downlink_scheduler() {
         .unwrap();
 
     run_scheduler_test(&DownlinkTest {
-        name: "cunconfirmed data".into(),
+        name: "unconfirmed data".into(),
         device_queue_items: vec![device_queue::DeviceQueueItem {
             id: Uuid::nil(),
             dev_eui: dev.dev_eui.clone(),
@@ -226,7 +251,7 @@ async fn test_downlink_scheduler() {
         .unwrap();
 
     run_scheduler_test(&DownlinkTest {
-        name: "cunconfirmed data".into(),
+        name: "unconfirmed data".into(),
         device_queue_items: vec![device_queue::DeviceQueueItem {
             id: Uuid::nil(),
             dev_eui: dev.dev_eui.clone(),