amt: use workqueue for gateway side message handling

There are some synchronization issues(amt->status, amt->req_cnt, etc)
if the interface is in gateway mode because gateway message handlers
are processed concurrently.
This applies a work queue for processing these messages instead of
expanding the locking context.

So, the purposes of this patch are to fix exist race conditions and to make
gateway to be able to validate a gateway status more correctly.

When the AMT gateway interface is created, it tries to establish to relay.
The establishment step looks stateless, but it should be managed well.
In order to handle messages in the gateway, it saves the current
status(i.e. AMT_STATUS_XXX).
This patch makes gateway code to be worked with a single thread.

Now, all messages except the multicast are triggered(received or
delay expired), and these messages will be stored in the event
queue(amt->events).
Then, the single worker processes stored messages asynchronously one
by one.
The multicast data message type will be still processed immediately.

Now, amt->lock is only needed to access the event queue(amt->events)
if an interface is the gateway mode.

Fixes: cbc21dc1cfe9 ("amt: add data plane of amt interface")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/include/net/amt.h b/include/net/amt.h
index 0e40c3d64fcf..08fc30cf2f34 100644
--- a/include/net/amt.h
+++ b/include/net/amt.h
@@ -78,6 +78,15 @@ enum amt_status {
 
 #define AMT_STATUS_MAX (__AMT_STATUS_MAX - 1)
 
+/* Gateway events only */
+enum amt_event {
+	AMT_EVENT_NONE,
+	AMT_EVENT_RECEIVE,
+	AMT_EVENT_SEND_DISCOVERY,
+	AMT_EVENT_SEND_REQUEST,
+	__AMT_EVENT_MAX,
+};
+
 struct amt_header {
 #if defined(__LITTLE_ENDIAN_BITFIELD)
 	u8 type:4,
@@ -292,6 +301,12 @@ struct amt_group_node {
 	struct hlist_head	sources[];
 };
 
+#define AMT_MAX_EVENTS	16
+struct amt_events {
+	enum amt_event event;
+	struct sk_buff *skb;
+};
+
 struct amt_dev {
 	struct net_device       *dev;
 	struct net_device       *stream_dev;
@@ -308,6 +323,7 @@ struct amt_dev {
 	struct delayed_work     req_wq;
 	/* Protected by RTNL */
 	struct delayed_work     secret_wq;
+	struct work_struct	event_wq;
 	/* AMT status */
 	enum amt_status		status;
 	/* Generated key */
@@ -345,6 +361,10 @@ struct amt_dev {
 	/* Used only in gateway mode */
 	u64			mac:48,
 				reserved:16;
+	/* AMT gateway side message handler queue */
+	struct amt_events	events[AMT_MAX_EVENTS];
+	u8			event_idx;
+	u8			nr_events;
 };
 
 #define AMT_TOS			0xc0