From b1671f1aac45ebc4aa92b83cc20ed31c25637f39 Mon Sep 17 00:00:00 2001
From: Ulf Lilleengen <ulf.lilleengen@gmail.com>
Date: Sat, 25 Jan 2025 16:07:53 +0100
Subject: [PATCH] fix: use async version of send for gatt replies

* Print warning if outbound channel is full on reply drop
---
 examples/apps/src/ble_bas_peripheral.rs | 31 ++++++++++++++++++-------
 host/src/gatt.rs                        | 22 +++++++++++++++++-
 2 files changed, 44 insertions(+), 9 deletions(-)

diff --git a/examples/apps/src/ble_bas_peripheral.rs b/examples/apps/src/ble_bas_peripheral.rs
index b2d1282b..5e1aae01 100644
--- a/examples/apps/src/ble_bas_peripheral.rs
+++ b/examples/apps/src/ble_bas_peripheral.rs
@@ -119,15 +119,30 @@ async fn gatt_events_task(server: &Server<'_>, conn: &Connection<'_>) -> Result<
                 // the protocol details
                 match data.process(server).await {
                     // Server processing emits
-                    Ok(Some(GattEvent::Read(event))) => {
-                        if event.handle() == level.handle {
-                            let value = server.get(&level);
-                            info!("[gatt] Read Event to Level Characteristic: {:?}", value);
+                    Ok(Some(event)) => {
+                        match &event {
+                            GattEvent::Read(event) => {
+                                if event.handle() == level.handle {
+                                    let value = server.get(&level);
+                                    info!("[gatt] Read Event to Level Characteristic: {:?}", value);
+                                }
+                            }
+                            GattEvent::Write(event) => {
+                                if event.handle() == level.handle {
+                                    info!("[gatt] Write Event to Level Characteristic: {:?}", event.data());
+                                }
+                            }
                         }
-                    }
-                    Ok(Some(GattEvent::Write(event))) => {
-                        if event.handle() == level.handle {
-                            info!("[gatt] Write Event to Level Characteristic: {:?}", event.data());
+
+                        // This step is also performed at drop(), but writing it explicitly is necessary
+                        // in order to ensure reply is sent.
+                        match event.accept() {
+                            Ok(reply) => {
+                                reply.send().await;
+                            }
+                            Err(e) => {
+                                warn!("[gatt] error sending response: {:?}", e);
+                            }
                         }
                     }
                     Ok(_) => {}
diff --git a/host/src/gatt.rs b/host/src/gatt.rs
index b4d3e771..43daf6d1 100644
--- a/host/src/gatt.rs
+++ b/host/src/gatt.rs
@@ -103,6 +103,24 @@ pub enum GattEvent<'stack, 'server> {
     Write(WriteEvent<'stack, 'server>),
 }
 
+impl<'stack, 'server> GattEvent<'stack, 'server> {
+    /// Accept the event, making it processed by the server.
+    pub fn accept(self) -> Result<Reply<'stack>, Error> {
+        match self {
+            Self::Read(e) => e.accept(),
+            Self::Write(e) => e.accept(),
+        }
+    }
+
+    /// Reject the event with the provided error code, it will not be processed by the attribute server.
+    pub fn reject(self, err: AttErrorCode) -> Result<Reply<'stack>, Error> {
+        match self {
+            Self::Read(e) => e.reject(err),
+            Self::Write(e) => e.reject(err),
+        }
+    }
+}
+
 /// An event returned while processing GATT requests.
 pub struct ReadEvent<'stack, 'server> {
     value_handle: u16,
@@ -290,7 +308,9 @@ impl<'stack> Reply<'stack> {
 impl Drop for Reply<'_> {
     fn drop(&mut self) {
         if let Some(pdu) = self.pdu.take() {
-            let _ = self.connection.try_send(pdu);
+            if self.connection.try_send(pdu).is_err() {
+                warn!("[gatt] error sending reply (outbound buffer full)");
+            }
         }
     }
 }