Bluetooth: hci_sock: Add support for BT_{SND,RCV}BUF

This adds support for BT_{SND,RCV}BUF so userspace can set MTU based on
the channel usage.

Fixes: https://github.com/bluez/bluez/issues/201

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/hci_sock.c

@@ -57,6 +57,7 @@ struct hci_pinfo {
 	unsigned long     flags;
 	__u32             cookie;
 	char              comm[TASK_COMM_LEN];
+	__u16             mtu;
 };
 
 static struct hci_dev *hci_hdev_from_sock(struct sock *sk)
@@ -1374,6 +1375,10 @@ static int hci_sock_bind(struct socket *sock, struct sockaddr *addr,
 		break;
 	}
 
+	/* Default MTU to HCI_MAX_FRAME_SIZE if not set */
+	if (!hci_pi(sk)->mtu)
+		hci_pi(sk)->mtu = HCI_MAX_FRAME_SIZE;
+
 	sk->sk_state = BT_BOUND;
 
 done:
@@ -1719,7 +1724,7 @@ static int hci_sock_sendmsg(struct socket *sock, struct msghdr *msg,
 	if (flags & ~(MSG_DONTWAIT | MSG_NOSIGNAL | MSG_ERRQUEUE | MSG_CMSG_COMPAT))
 		return -EINVAL;
 
-	if (len < 4 || len > HCI_MAX_FRAME_SIZE)
+	if (len < 4 || len > hci_pi(sk)->mtu)
 		return -EINVAL;
 
 	buf = kmalloc(len, GFP_KERNEL);
@@ -1849,18 +1854,15 @@ static int hci_sock_sendmsg(struct socket *sock, struct msghdr *msg,
 	goto done;
 }
 
-static int hci_sock_setsockopt(struct socket *sock, int level, int optname,
-			       sockptr_t optval, unsigned int len)
+static int hci_sock_setsockopt_old(struct socket *sock, int level, int optname,
+				   sockptr_t optval, unsigned int len)
 {
 	struct hci_ufilter uf = { .opcode = 0 };
 	struct sock *sk = sock->sk;
 	int err = 0, opt = 0;
 
 	BT_DBG("sk %p, opt %d", sk, optname);
 
-	if (level != SOL_HCI)
-		return -ENOPROTOOPT;
-
 	lock_sock(sk);
 
 	if (hci_pi(sk)->channel != HCI_CHANNEL_RAW) {
@@ -1935,18 +1937,63 @@ static int hci_sock_setsockopt(struct socket *sock, int level, int optname,
 	return err;
 }
 
-static int hci_sock_getsockopt(struct socket *sock, int level, int optname,
-			       char __user *optval, int __user *optlen)
+static int hci_sock_setsockopt(struct socket *sock, int level, int optname,
+			       sockptr_t optval, unsigned int len)
 {
-	struct hci_ufilter uf;
 	struct sock *sk = sock->sk;
-	int len, opt, err = 0;
+	int err = 0, opt = 0;
 
 	BT_DBG("sk %p, opt %d", sk, optname);
 
-	if (level != SOL_HCI)
+	if (level == SOL_HCI)
+		return hci_sock_setsockopt_old(sock, level, optname, optval,
+					       len);
+
+	if (level != SOL_BLUETOOTH)
 		return -ENOPROTOOPT;
 
+	lock_sock(sk);
+
+	switch (optname) {
+	case BT_SNDMTU:
+	case BT_RCVMTU:
+		switch (hci_pi(sk)->channel) {
+		/* Don't allow changing MTU for channels that are meant for HCI
+		 * traffic only.
+		 */
+		case HCI_CHANNEL_RAW:
+		case HCI_CHANNEL_USER:
+			err = -ENOPROTOOPT;
+			goto done;
+		}
+
+		if (copy_from_sockptr(&opt, optval, sizeof(u16))) {
+			err = -EFAULT;
+			break;
+		}
+
+		hci_pi(sk)->mtu = opt;
+		break;
+
+	default:
+		err = -ENOPROTOOPT;
+		break;
+	}
+
+done:
+	release_sock(sk);
+	return err;
+}
+
+static int hci_sock_getsockopt_old(struct socket *sock, int level, int optname,
+				   char __user *optval, int __user *optlen)
+{
+	struct hci_ufilter uf;
+	struct sock *sk = sock->sk;
+	int len, opt, err = 0;
+
+	BT_DBG("sk %p, opt %d", sk, optname);
+
 	if (get_user(len, optlen))
 		return -EFAULT;
 
@@ -2004,6 +2051,39 @@ static int hci_sock_getsockopt(struct socket *sock, int level, int optname,
 	return err;
 }
 
+static int hci_sock_getsockopt(struct socket *sock, int level, int optname,
+			       char __user *optval, int __user *optlen)
+{
+	struct sock *sk = sock->sk;
+	int err = 0;
+
+	BT_DBG("sk %p, opt %d", sk, optname);
+
+	if (level == SOL_HCI)
+		return hci_sock_getsockopt_old(sock, level, optname, optval,
+					       optlen);
+
+	if (level != SOL_BLUETOOTH)
+		return -ENOPROTOOPT;
+
+	lock_sock(sk);
+
+	switch (optname) {
+	case BT_SNDMTU:
+	case BT_RCVMTU:
+		if (put_user(hci_pi(sk)->mtu, (u16 __user *)optval))
+			err = -EFAULT;
+		break;
+
+	default:
+		err = -ENOPROTOOPT;
+		break;
+	}
+
+	release_sock(sk);
+	return err;
+}
+
 static const struct proto_ops hci_sock_ops = {
 	.family		= PF_BLUETOOTH,
 	.owner		= THIS_MODULE,