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

[Luiz Augusto von Dentz <luiz.dentz@xxxxxxxxx>]

From: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>

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@xxxxxxxxx>
---
 net/bluetooth/hci_sock.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
index 31a2eefede3c..8cebf8a0e85d 100644
--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c
@@ -57,6 +57,7 @@ struct hci_pinfo {
 	unsigned long     flags;
 	__u32             cookie;
 	char              comm[TASK_COMM_LEN];
+	unsigned int      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:
@@ -1704,7 +1709,7 @@ 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;
 
 	skb = bt_skb_sendmsg(sk, msg, len, len, 0, 0);
@@ -1899,6 +1904,16 @@ static int hci_sock_setsockopt(struct socket *sock, int level, int optname,
 		}
 		break;
 
+	case BT_SNDMTU:
+	case BT_RCVMTU:
+		if (copy_from_sockptr(&opt, optval, sizeof(u16))) {
+			err = -EFAULT;
+			break;
+		}
+
+		hci_pi(sk)->mtu = opt;
+		break;
+
 	default:
 		err = -ENOPROTOOPT;
 		break;
@@ -1968,6 +1983,12 @@ static int hci_sock_getsockopt(struct socket *sock, int level, int optname,
 			err = -EFAULT;
 		break;
 
+	case BT_SNDMTU:
+	case BT_RCVMTU:
+		if (put_user(hci_pi(sk)->mtu, (u32 __user *)optval))
+			err = -EFAULT;
+		break;
+
 	default:
 		err = -ENOPROTOOPT;
 		break;
-- 
2.31.1