Bluetooth: Add support for BT_PKT_STATUS CMSG data for SCO connections

This change adds support for reporting the BT_PKT_STATUS to the socket
CMSG data to allow the implementation of a packet loss correction on
erroneous data received on the SCO socket.

The patch was partially developed by Marcel Holtmann and validated by
Hsin-yu Chao.

Signed-off-by: Alain Michaud <alainm@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/af_bluetooth.c

@@ -286,6 +286,9 @@ int bt_sock_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 		if (msg->msg_name && bt_sk(sk)->skb_msg_name)
 			bt_sk(sk)->skb_msg_name(skb, msg->msg_name,
 						&msg->msg_namelen);
+
+		if (bt_sk(sk)->skb_put_cmsg)
+			bt_sk(sk)->skb_put_cmsg(skb, msg, sk);
 	}
 
 	skb_free_datagram(sk, skb);

net/bluetooth/hci_core.c

@@ -4554,6 +4554,7 @@ static void hci_scodata_packet(struct hci_dev *hdev, struct sk_buff *skb)
 
 	if (conn) {
 		/* Send to upper protocol */
+		bt_cb(skb)->sco.pkt_status = flags & 0x03;
 		sco_recv_scodata(conn, skb);
 		return;
 	} else {

net/bluetooth/sco.c

@@ -66,6 +66,7 @@ struct sco_pinfo {
 	bdaddr_t	dst;
 	__u32		flags;
 	__u16		setting;
+	__u8		cmsg_mask;
 	struct sco_conn	*conn;
 };
 
@@ -449,6 +450,15 @@ static void sco_sock_close(struct sock *sk)
 	sco_sock_kill(sk);
 }
 
+static void sco_skb_put_cmsg(struct sk_buff *skb, struct msghdr *msg,
+			     struct sock *sk)
+{
+	if (sco_pi(sk)->cmsg_mask & SCO_CMSG_PKT_STATUS)
+		put_cmsg(msg, SOL_BLUETOOTH, BT_SCM_PKT_STATUS,
+			 sizeof(bt_cb(skb)->sco.pkt_status),
+			 &bt_cb(skb)->sco.pkt_status);
+}
+
 static void sco_sock_init(struct sock *sk, struct sock *parent)
 {
 	BT_DBG("sk %p", sk);
@@ -457,6 +467,8 @@ static void sco_sock_init(struct sock *sk, struct sock *parent)
 		sk->sk_type = parent->sk_type;
 		bt_sk(sk)->flags = bt_sk(parent)->flags;
 		security_sk_clone(parent, sk);
+	} else {
+		bt_sk(sk)->skb_put_cmsg = sco_skb_put_cmsg;
 	}
 }
 
@@ -846,6 +858,18 @@ static int sco_sock_setsockopt(struct socket *sock, int level, int optname,
 		sco_pi(sk)->setting = voice.setting;
 		break;
 
+	case BT_PKT_STATUS:
+		if (get_user(opt, (u32 __user *)optval)) {
+			err = -EFAULT;
+			break;
+		}
+
+		if (opt)
+			sco_pi(sk)->cmsg_mask |= SCO_CMSG_PKT_STATUS;
+		else
+			sco_pi(sk)->cmsg_mask &= SCO_CMSG_PKT_STATUS;
+		break;
+
 	default:
 		err = -ENOPROTOOPT;
 		break;
@@ -923,6 +947,7 @@ static int sco_sock_getsockopt(struct socket *sock, int level, int optname,
 	int len, err = 0;
 	struct bt_voice voice;
 	u32 phys;
+	int pkt_status;
 
 	BT_DBG("sk %p", sk);
 
@@ -969,6 +994,13 @@ static int sco_sock_getsockopt(struct socket *sock, int level, int optname,
 			err = -EFAULT;
 		break;
 
+	case BT_PKT_STATUS:
+		pkt_status = (sco_pi(sk)->cmsg_mask & SCO_CMSG_PKT_STATUS);
+
+		if (put_user(pkt_status, (int __user *)optval))
+			err = -EFAULT;
+		break;
+
 	default:
 		err = -ENOPROTOOPT;
 		break;