From 6278a71040ef070f2a15e07a43b449ce5035287a Mon Sep 17 00:00:00 2001
From: Sebastian Urban <surban@surban.net>
Date: Sat, 12 Jun 2021 11:56:01 +0200
Subject: [PATCH] gatt-database: No multiple calls to AcquireWrite

This checks if an outstanding call to AcquireWrite is already in
progress. If so, the write request is placed into the queue, but
AcquireWrite is not called again. When a response to AcquireWrite is
received, acquire_write_reply sends all queued writes over the acquired
socket.

Making multiple simultaneous calls to AcquireWrite makes no sense,
as this would open multiple socket pairs and only the last returned
socket would be used for further writes.
---
 src/gatt-database.c | 41 +++++++++++++++++++++++++++++++++--------
 1 file changed, 33 insertions(+), 8 deletions(-)

--- a/src/gatt-database.c
+++ b/src/gatt-database.c
@@ -2381,6 +2381,26 @@ static struct pending_op *send_write(str
 	return NULL;
 }
 
+static void flush_pending_write(void *data, void *user_data)
+{
+	GDBusProxy *proxy = user_data;
+	struct pending_op *op = data;
+
+	if (g_dbus_proxy_method_call(proxy, "WriteValue", write_setup_cb,
+					write_reply_cb,
+					op, pending_op_free) == TRUE)
+		return;
+
+	pending_op_free(op);
+}
+
+static void flush_pending_writes(GDBusProxy *proxy,
+					struct queue *owner_queue)
+{
+	queue_foreach(owner_queue, flush_pending_write, proxy);
+	queue_remove_all(owner_queue, NULL, NULL, NULL);
+}
+
 static bool sock_hup(struct io *io, void *user_data)
 {
 	struct external_chrc *chrc = user_data;
@@ -2491,18 +2511,19 @@ static void acquire_write_reply(DBusMess
 
 	chrc->write_io = sock_io_new(fd, chrc);
 
-	if (sock_io_send(chrc->write_io, op->data.iov_base,
-				op->data.iov_len) < 0)
-		goto retry;
+	while ((op = queue_peek_head(chrc->pending_writes)) != NULL) {
+		if (sock_io_send(chrc->write_io, op->data.iov_base,
+					op->data.iov_len) < 0)
+			goto retry;
 
-	gatt_db_attribute_write_result(op->attrib, op->id, 0);
+		gatt_db_attribute_write_result(op->attrib, op->id, 0);
+		pending_op_free(op);
+	}
 
 	return;
 
 retry:
-	send_write(op->device, op->attrib, chrc->proxy, NULL, op->id,
-				op->data.iov_base, op->data.iov_len, 0,
-				op->link_type, false, false);
+	flush_pending_writes(chrc->proxy, chrc->pending_writes);
 }
 
 static void acquire_write_setup(DBusMessageIter *iter, void *user_data)
@@ -2530,14 +2551,18 @@ static struct pending_op *acquire_write(
 					uint8_t link_type)
 {
 	struct pending_op *op;
+	bool acquiring = !queue_isempty(chrc->pending_writes);
 
 	op = pending_write_new(device, chrc->pending_writes, attrib, id, value,
 				len, 0, link_type, false, false);
 
+	if (acquiring)
+		return op;
+
 	if (g_dbus_proxy_method_call(chrc->proxy, "AcquireWrite",
 					acquire_write_setup,
 					acquire_write_reply,
-					op, pending_op_free))
+					op, NULL))
 		return op;
 
 	pending_op_free(op);