Bluetooth: L2CAP: Add module option to enable ECRED mode

This should make it safe to have the code upstream without affecting
stable systems since there are a few details not sort out with ECRED
mode e.g: how to initiate multiple connections at once.
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

include/net/bluetooth/l2cap.h

@@ -958,6 +958,7 @@ static inline long l2cap_chan_no_get_sndtimeo(struct l2cap_chan *chan)
 }
 
 extern bool disable_ertm;
+extern bool enable_ecred;
 
 int l2cap_init_sockets(void);
 void l2cap_cleanup_sockets(void);

net/bluetooth/l2cap_core.c

@@ -45,6 +45,7 @@
 #define LE_FLOWCTL_MAX_CREDITS 65535
 
 bool disable_ertm;
+bool enable_ecred;
 
 static u32 l2cap_feat_mask = L2CAP_FEAT_FIXED_CHAN | L2CAP_FEAT_UCD;
 
@@ -5849,6 +5850,9 @@ static inline int l2cap_ecred_conn_req(struct l2cap_conn *conn,
 	int i, num_scid;
 	bool defer = false;
 
+	if (!enable_ecred)
+		return -EINVAL;
+
 	if (cmd_len < sizeof(*req) || cmd_len - sizeof(*req) % sizeof(u16)) {
 		result = L2CAP_CR_LE_INVALID_PARAMS;
 		goto response;
@@ -6092,6 +6096,9 @@ static inline int l2cap_ecred_reconf_req(struct l2cap_conn *conn,
 	struct l2cap_chan *chan;
 	int i, num_scid;
 
+	if (!enable_ecred)
+		return -EINVAL;
+
 	if (cmd_len < sizeof(*req) || cmd_len - sizeof(*req) % sizeof(u16)) {
 		result = L2CAP_CR_LE_INVALID_PARAMS;
 		goto respond;
@@ -7723,7 +7730,12 @@ int l2cap_chan_connect(struct l2cap_chan *chan, __le16 psm, u16 cid,
 	case L2CAP_MODE_BASIC:
 		break;
 	case L2CAP_MODE_LE_FLOWCTL:
+		break;
 	case L2CAP_MODE_EXT_FLOWCTL:
+		if (!enable_ecred) {
+			err = -EOPNOTSUPP;
+			goto done;
+		}
 		break;
 	case L2CAP_MODE_ERTM:
 	case L2CAP_MODE_STREAMING:
@@ -8301,3 +8313,6 @@ void l2cap_exit(void)
 
 module_param(disable_ertm, bool, 0644);
 MODULE_PARM_DESC(disable_ertm, "Disable enhanced retransmission mode");
+
+module_param(enable_ecred, bool, 0644);
+MODULE_PARM_DESC(enable_ecred, "Enable enhanced credit flow control mode");

net/bluetooth/l2cap_sock.c

@@ -273,7 +273,12 @@ static int l2cap_sock_listen(struct socket *sock, int backlog)
 	switch (chan->mode) {
 	case L2CAP_MODE_BASIC:
 	case L2CAP_MODE_LE_FLOWCTL:
+		break;
 	case L2CAP_MODE_EXT_FLOWCTL:
+		if (!enable_ecred) {
+			err = -EOPNOTSUPP;
+			goto done;
+		}
 		break;
 	case L2CAP_MODE_ERTM:
 	case L2CAP_MODE_STREAMING: