From 4f43777297880d6deb0509eec2dd8a0ae3d5b88c Mon Sep 17 00:00:00 2001
From: Debarshi Ray <rishi@gnu.org>
Date: Thu, 29 Sep 2011 23:06:03 +0300
Subject: [PATCH 16/18] IdleConnection: Prevent overlapping and duplicate
 sends

If the timeout is low or the underlying network is bad, then successive
calls to idle_server_connection_send_async can overlap. ie. a newer
operation is started before all the earlier ones have finished. The
underlying GOutputStream does not allow this.

Therefore, we add a new private member to track whether we are in the
middle of sending something or not, and refuse to send anything new in
the current timeout interval if that is the case.

Similarly, the same message can be submitted more than once if we do
not remove from the queue those that have been passed to
idle_server_connection_send_async, but has not had their operations
finish. In case an error occurs, the messages are restored to the
front of the queue for re-submission in the next interval.

Fixes: https://bugs.freedesktop.org/37145
---
 src/idle-connection.c |   44 +++++++++++++++++++++++++++++---------------
 1 files changed, 29 insertions(+), 15 deletions(-)

diff --git a/src/idle-connection.c b/src/idle-connection.c
index 8fc7713..b6e1039 100644
--- a/src/idle-connection.c
+++ b/src/idle-connection.c
@@ -93,7 +93,7 @@ struct _IdleOutputPendingMsg {
 
 struct _MsgQueueTimeoutData {
 	IdleConnection *conn;
-	gint limit;
+	GSList *sent_msgs;
 };
 
 struct _SendWithPriorityData {
@@ -178,6 +178,9 @@ struct _IdleConnectionPrivate {
 	/* output message queue */
 	GQueue *msg_queue;
 
+	/* has it submitted a message for sending and waiting for acknowledgement */
+	gboolean msg_sending;
+
 	/* UNIX time the last message was sent on */
 	time_t last_msg_sent;
 
@@ -823,29 +826,34 @@ static gboolean keepalive_timeout_cb(gpointer user_data) {
 	return TRUE;
 }
 
+static void _sent_msgs_foreach_free(gpointer data) {
+	idle_output_pending_msg_free((IdleOutputPendingMsg *) data);
+}
+
+static void _restore_msg_to_queue(gpointer data, gpointer user_data) {
+	GQueue *msg_queue = (GQueue *) user_data;
+	g_queue_push_head(msg_queue, data);
+}
+
 static void _msg_queue_timeout_ready(GObject *source_object, GAsyncResult *res, gpointer user_data) {
 	IdleServerConnection *sconn = IDLE_SERVER_CONNECTION(source_object);
 	MsgQueueTimeoutData *data = (MsgQueueTimeoutData *) user_data;
 	IdleConnection *conn = data->conn;
 	IdleConnectionPrivate *priv = IDLE_CONNECTION_GET_PRIVATE(conn);
-	IdleOutputPendingMsg *output_msg;
-	int i;
-	int limit = data->limit;
+	GSList *sent_msgs = data->sent_msgs;
 	GError *error = NULL;
 
 	g_slice_free(MsgQueueTimeoutData, data);
+	priv->msg_sending = FALSE;
 
 	if (!idle_server_connection_send_finish(sconn, res, &error)) {
 		IDLE_DEBUG("idle_server_connection_send failed: %s", error->message);
 		g_error_free(error);
+		g_slist_foreach(sent_msgs, _restore_msg_to_queue, priv->msg_queue);
 		return;
 	}
 
-	for (i = 0; i < limit; i++) {
-		output_msg = g_queue_pop_head(priv->msg_queue);
-		idle_output_pending_msg_free(output_msg);
-	}
-
+	g_slist_free_full(sent_msgs, _sent_msgs_foreach_free);
 	priv->last_msg_sent = time(NULL);
 }
 
@@ -867,17 +875,25 @@ static gboolean msg_queue_timeout_cb(gpointer user_data) {
 		return FALSE;
 	}
 
-	output_msg = g_queue_peek_head(priv->msg_queue);
+	if (priv->msg_sending)
+		return TRUE;
+
+	output_msg = g_queue_pop_head(priv->msg_queue);
 
 	if (output_msg == NULL) {
 		priv->msg_queue_timeout = 0;
 		return FALSE;
 	}
 
+	data = g_slice_new0(MsgQueueTimeoutData);
+	data->conn = conn;
+	data->sent_msgs = g_slist_prepend(data->sent_msgs, output_msg);
+
 	g_strlcpy(msg, output_msg->message, IRC_MSG_MAXLEN + 3);
 
 	for (i = 1; i < MSG_QUEUE_UNLOAD_AT_A_TIME; i++) {
-		output_msg = g_queue_peek_nth(priv->msg_queue, i);
+		output_msg = (IdleOutputPendingMsg *) g_queue_pop_head(priv->msg_queue);
+		data->sent_msgs = g_slist_prepend(data->sent_msgs, output_msg);
 
 		if ((output_msg != NULL) && ((strlen(msg) + strlen(output_msg->message)) < IRC_MSG_MAXLEN + 2))
 			strcat(msg, output_msg->message);
@@ -885,11 +901,9 @@ static gboolean msg_queue_timeout_cb(gpointer user_data) {
 			break;
 	}
 
-	data = g_slice_new0(MsgQueueTimeoutData);
-	data->conn = conn;
-	data->limit = i;
-
 	idle_server_connection_send_async(priv->conn, msg, NULL, _msg_queue_timeout_ready, data);
+	priv->msg_sending = TRUE;
+
 	return TRUE;
 }
 
-- 
1.7.6.2