[RFC net-next 09/15] net: cpc: add support for RST frames

["Damien Riégel" <damien.riegel@silabs.com>]

Reset frames are used to either disconnect an endpoint or to signal that
a frame is targeting an endpoint that is not connected.

Signed-off-by: Damien Riégel <damien.riegel@silabs.com>
---
 drivers/net/cpc/cpc.h       |  1 +
 drivers/net/cpc/endpoint.c  | 16 ++++++++++++----
 drivers/net/cpc/interface.c |  9 ++++++++-
 drivers/net/cpc/protocol.c  | 32 +++++++++++++++++++++++++++++++-
 drivers/net/cpc/protocol.h  |  2 ++
 5 files changed, 54 insertions(+), 6 deletions(-)

diff --git a/drivers/net/cpc/cpc.h b/drivers/net/cpc/cpc.h
index d316fce4ad7..34ee519d907 100644
--- a/drivers/net/cpc/cpc.h
+++ b/drivers/net/cpc/cpc.h
@@ -94,6 +94,7 @@ struct cpc_endpoint *cpc_endpoint_new(struct cpc_interface *intf, u8 id, const c
 void cpc_endpoint_unregister(struct cpc_endpoint *ep);
 
 int cpc_endpoint_connect(struct cpc_endpoint *ep);
+void __cpc_endpoint_disconnect(struct cpc_endpoint *ep, bool send_rst);
 void cpc_endpoint_disconnect(struct cpc_endpoint *ep);
 int cpc_endpoint_write(struct cpc_endpoint *ep, struct sk_buff *skb);
 void cpc_endpoint_set_ops(struct cpc_endpoint *ep, struct cpc_endpoint_ops *ops);
diff --git a/drivers/net/cpc/endpoint.c b/drivers/net/cpc/endpoint.c
index e6b2793d842..7e2f623fb8e 100644
--- a/drivers/net/cpc/endpoint.c
+++ b/drivers/net/cpc/endpoint.c
@@ -253,6 +253,17 @@ int cpc_endpoint_connect(struct cpc_endpoint *ep)
 	return err;
 }
 
+void __cpc_endpoint_disconnect(struct cpc_endpoint *ep, bool send_rst)
+{
+	if (!test_and_clear_bit(CPC_ENDPOINT_UP, &ep->flags))
+		return;
+
+	cpc_interface_remove_rx_endpoint(ep);
+
+	if (send_rst)
+		cpc_protocol_send_rst(ep->intf, ep->id);
+}
+
 /**
  * cpc_endpoint_disconnect - Disconnect endpoint from remote.
  * @ep: Endpoint handle.
@@ -264,10 +275,7 @@ int cpc_endpoint_connect(struct cpc_endpoint *ep)
  */
 void cpc_endpoint_disconnect(struct cpc_endpoint *ep)
 {
-	if (!test_and_clear_bit(CPC_ENDPOINT_UP, &ep->flags))
-		return;
-
-	cpc_interface_remove_rx_endpoint(ep);
+	__cpc_endpoint_disconnect(ep, true);
 }
 
 /**
diff --git a/drivers/net/cpc/interface.c b/drivers/net/cpc/interface.c
index d6b04588a61..30e7976355c 100644
--- a/drivers/net/cpc/interface.c
+++ b/drivers/net/cpc/interface.c
@@ -28,6 +28,10 @@ static void cpc_interface_rx_work(struct work_struct *work)
 
 		ep = cpc_interface_get_endpoint(intf, ep_id);
 		if (!ep) {
+			if (type != CPC_FRAME_TYPE_RST) {
+				dev_dbg(&intf->dev, "ep%u not allocated (%d)\n", ep_id, type);
+				cpc_protocol_send_rst(intf, ep_id);
+			}
 			kfree_skb(skb);
 			continue;
 		}
@@ -39,8 +43,11 @@ static void cpc_interface_rx_work(struct work_struct *work)
 		case CPC_FRAME_TYPE_SYN:
 			cpc_protocol_on_syn(ep, skb);
 			break;
-		default:
+		case CPC_FRAME_TYPE_RST:
+			dev_dbg(&ep->dev, "reset\n");
 			kfree_skb(skb);
+			cpc_protocol_on_rst(ep);
+			break;
 		}
 
 		cpc_endpoint_put(ep);
diff --git a/drivers/net/cpc/protocol.c b/drivers/net/cpc/protocol.c
index db7ac0dc066..faacd0f42ad 100644
--- a/drivers/net/cpc/protocol.c
+++ b/drivers/net/cpc/protocol.c
@@ -60,6 +60,28 @@ static void __cpc_protocol_send_ack(struct cpc_endpoint *ep)
 	cpc_interface_send_frame(ep->intf, skb);
 }
 
+/**
+ * cpc_protocol_send_rst - send a RST frame
+ * @intf: interface pointer
+ * @ep_id: endpoint id
+ */
+void cpc_protocol_send_rst(struct cpc_interface *intf, u8 ep_id)
+{
+	struct cpc_header hdr = {
+		.ctrl = cpc_header_get_ctrl(CPC_FRAME_TYPE_RST, false),
+		.ep_id = ep_id,
+	};
+	struct sk_buff *skb;
+
+	skb = cpc_skb_alloc(0, GFP_KERNEL);
+	if (!skb)
+		return;
+
+	memcpy(skb_push(skb, sizeof(hdr)), &hdr, sizeof(hdr));
+
+	cpc_interface_send_frame(intf, skb);
+}
+
 static void cpc_protocol_on_tx_complete(struct sk_buff *skb)
 {
 	struct cpc_endpoint *ep = cpc_skb_get_ctx(skb);
@@ -228,8 +250,11 @@ void cpc_protocol_on_syn(struct cpc_endpoint *ep, struct sk_buff *skb)
 {
 	mutex_lock(&ep->tcb.lock);
 
-	if (!__cpc_protocol_is_syn_ack_valid(ep, skb))
+	if (!__cpc_protocol_is_syn_ack_valid(ep, skb)) {
+		cpc_protocol_send_rst(ep->intf, ep->id);
+
 		goto out;
+	}
 
 	__cpc_protocol_receive_ack(ep,
 				   cpc_header_get_recv_wnd(skb->data),
@@ -253,6 +278,11 @@ void cpc_protocol_on_syn(struct cpc_endpoint *ep, struct sk_buff *skb)
 	kfree_skb(skb);
 }
 
+void cpc_protocol_on_rst(struct cpc_endpoint *ep)
+{
+	__cpc_endpoint_disconnect(ep, false);
+}
+
 /**
  * __cpc_protocol_write() - Write a frame.
  * @ep: Endpoint handle.
diff --git a/drivers/net/cpc/protocol.h b/drivers/net/cpc/protocol.h
index e67f0f6d025..977bb7c1450 100644
--- a/drivers/net/cpc/protocol.h
+++ b/drivers/net/cpc/protocol.h
@@ -19,7 +19,9 @@ int __cpc_protocol_write(struct cpc_endpoint *ep, struct cpc_header *hdr, struct
 
 void cpc_protocol_on_data(struct cpc_endpoint *ep, struct sk_buff *skb);
 void cpc_protocol_on_syn(struct cpc_endpoint *ep, struct sk_buff *skb);
+void cpc_protocol_on_rst(struct cpc_endpoint *ep);
 
+void cpc_protocol_send_rst(struct cpc_interface *intf, u8 ep_id);
 int cpc_protocol_send_syn(struct cpc_endpoint *ep);
 
 #endif
-- 
2.49.0