Bluetooth: Only enable L2CAP FCS for ERTM or streaming

This fixes a bug which caused the FCS setting to show L2CAP_FCS_CRC16
with L2CAP modes other than ERTM or streaming.  At present, this only
affects the FCS value shown with getsockopt() for basic mode.
Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>

net/bluetooth/l2cap.c

@@ -3071,6 +3071,17 @@ static inline int l2cap_connect_rsp(struct l2cap_conn *conn, struct l2cap_cmd_hd
 	return 0;
 }
 
+static inline void set_default_fcs(struct l2cap_pinfo *pi)
+{
+	/* FCS is enabled only in ERTM or streaming mode, if one or both
+	 * sides request it.
+	 */
+	if (pi->mode != L2CAP_MODE_ERTM && pi->mode != L2CAP_MODE_STREAMING)
+		pi->fcs = L2CAP_FCS_NONE;
+	else if (!(pi->conf_state & L2CAP_CONF_NO_FCS_RECV))
+		pi->fcs = L2CAP_FCS_CRC16;
+}
+
 static inline int l2cap_config_req(struct l2cap_conn *conn, struct l2cap_cmd_hdr *cmd, u16 cmd_len, u8 *data)
 {
 	struct l2cap_conf_req *req = (struct l2cap_conf_req *) data;
@@ -3135,9 +3146,7 @@ static inline int l2cap_config_req(struct l2cap_conn *conn, struct l2cap_cmd_hdr
 		goto unlock;
 
 	if (l2cap_pi(sk)->conf_state & L2CAP_CONF_INPUT_DONE) {
-		if (!(l2cap_pi(sk)->conf_state & L2CAP_CONF_NO_FCS_RECV) ||
-		    l2cap_pi(sk)->fcs != L2CAP_FCS_NONE)
-			l2cap_pi(sk)->fcs = L2CAP_FCS_CRC16;
+		set_default_fcs(l2cap_pi(sk));
 
 		sk->sk_state = BT_CONNECTED;
 
@@ -3225,9 +3234,7 @@ static inline int l2cap_config_rsp(struct l2cap_conn *conn, struct l2cap_cmd_hdr
 	l2cap_pi(sk)->conf_state |= L2CAP_CONF_INPUT_DONE;
 
 	if (l2cap_pi(sk)->conf_state & L2CAP_CONF_OUTPUT_DONE) {
-		if (!(l2cap_pi(sk)->conf_state & L2CAP_CONF_NO_FCS_RECV) ||
-		    l2cap_pi(sk)->fcs != L2CAP_FCS_NONE)
-			l2cap_pi(sk)->fcs = L2CAP_FCS_CRC16;
+		set_default_fcs(l2cap_pi(sk));
 
 		sk->sk_state = BT_CONNECTED;
 		l2cap_pi(sk)->next_tx_seq = 0;