Bluetooth: Add RFCOMM option to use L2CAP ERTM mode

By default the RFCOMM layer would still use L2CAP basic mode. For testing
purposes this option enables RFCOMM to select enhanced retransmission
mode.
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/rfcomm/core.c

@@ -51,6 +51,7 @@
 static int disable_cfc = 0;
 static int channel_mtu = -1;
 static unsigned int l2cap_mtu = RFCOMM_MAX_L2CAP_MTU;
+static int l2cap_ertm = 0;
 
 static struct task_struct *rfcomm_thread;
 
@@ -702,6 +703,8 @@ static struct rfcomm_session *rfcomm_session_create(bdaddr_t *src, bdaddr_t *dst
 	sk = sock->sk;
 	lock_sock(sk);
 	l2cap_pi(sk)->imtu = l2cap_mtu;
+	if (l2cap_ertm)
+		l2cap_pi(sk)->mode = L2CAP_MODE_ERTM;
 	release_sock(sk);
 
 	s = rfcomm_session_add(sock, BT_BOUND);
@@ -2185,6 +2188,9 @@ MODULE_PARM_DESC(channel_mtu, "Default MTU for the RFCOMM channel");
 module_param(l2cap_mtu, uint, 0644);
 MODULE_PARM_DESC(l2cap_mtu, "Default MTU for the L2CAP connection");
 
+module_param(l2cap_ertm, bool, 0644);
+MODULE_PARM_DESC(l2cap_ertm, "Use L2CAP ERTM mode for connection");
+
 MODULE_AUTHOR("Marcel Holtmann <marcel@holtmann.org>");
 MODULE_DESCRIPTION("Bluetooth RFCOMM ver " VERSION);
 MODULE_VERSION(VERSION);