NFC: Send LLCP RR frames to acknowledge received I frames

In order to acknowledge an I frame, we have to either queue pending local
I frames or queue a receiver ready frame.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/nfc/llcp/commands.c

@@ -428,3 +428,27 @@ int nfc_llcp_send_i_frame(struct nfc_llcp_sock *sock,
 
 	return 0;
 }
+
+int nfc_llcp_send_rr(struct nfc_llcp_sock *sock)
+{
+	struct sk_buff *skb;
+	struct nfc_llcp_local *local;
+
+	pr_debug("Send rr nr %d\n", sock->recv_n);
+
+	local = sock->local;
+	if (local == NULL)
+		return -ENODEV;
+
+	skb = llcp_allocate_pdu(sock, LLCP_PDU_RR, LLCP_SEQUENCE_SIZE);
+	if (skb == NULL)
+		return -ENOMEM;
+
+	skb_put(skb, LLCP_SEQUENCE_SIZE);
+
+	skb->data[2] = sock->recv_n % 16;
+
+	skb_queue_head(&local->tx_queue, skb);
+
+	return 0;
+}

net/nfc/llcp/llcp.c

@@ -627,8 +627,9 @@ fail:
 
 }
 
-void nfc_llcp_queue_i_frames(struct nfc_llcp_sock *sock)
+int nfc_llcp_queue_i_frames(struct nfc_llcp_sock *sock)
 {
+	int nr_frames = 0;
 	struct nfc_llcp_local *local = sock->local;
 
 	pr_debug("Remote ready %d tx queue len %d remote rw %d",
@@ -651,7 +652,10 @@ void nfc_llcp_queue_i_frames(struct nfc_llcp_sock *sock)
 
 		skb_queue_tail(&local->tx_queue, pdu);
 		skb_queue_tail(&sock->tx_pending_queue, pending_pdu);
+		nr_frames++;
 	}
+
+	return nr_frames;
 }
 
 static void nfc_llcp_recv_hdlc(struct nfc_llcp_local *local,
@@ -716,7 +720,8 @@ static void nfc_llcp_recv_hdlc(struct nfc_llcp_local *local,
         else if (ptype == LLCP_PDU_RNR)
 		llcp_sock->remote_ready = false;
 
-	nfc_llcp_queue_i_frames(llcp_sock);
+	if (nfc_llcp_queue_i_frames(llcp_sock) == 0)
+		nfc_llcp_send_rr(llcp_sock);
 
 	release_sock(sk);
 	nfc_llcp_sock_put(llcp_sock);

net/nfc/llcp/llcp.h

@@ -165,7 +165,7 @@ u8 nfc_llcp_get_sdp_ssap(struct nfc_llcp_local *local,
 				struct nfc_llcp_sock *sock);
 u8 nfc_llcp_get_local_ssap(struct nfc_llcp_local *local);
 void nfc_llcp_put_ssap(struct nfc_llcp_local *local, u8 ssap);
-void nfc_llcp_queue_i_frames(struct nfc_llcp_sock *sock);
+int nfc_llcp_queue_i_frames(struct nfc_llcp_sock *sock);
 
 /* Sock API */
 struct sock *nfc_llcp_sock_alloc(struct socket *sock, int type, gfp_t gfp);
@@ -190,6 +190,7 @@ int nfc_llcp_send_dm(struct nfc_llcp_local *local, u8 ssap, u8 dsap, u8 reason);
 int nfc_llcp_send_disconnect(struct nfc_llcp_sock *sock);
 int nfc_llcp_send_i_frame(struct nfc_llcp_sock *sock,
 				struct msghdr *msg, size_t len);
+int nfc_llcp_send_rr(struct nfc_llcp_sock *sock);
 
 /* Socket API */
 int __init nfc_llcp_sock_init(void);