Bluetooth: Allow setting of L2CAP ERTM via socket option

To enable Enhanced Retransmission mode it needs to be set via a socket
option. A different mode can be set on a socket, but on listen() and
connect() the mode is checked and ERTM is only allowed if it is enabled
via the module parameter.
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

include/net/bluetooth/l2cap.h

@@ -190,7 +190,7 @@ struct l2cap_conf_rfc {
 #define L2CAP_MODE_RETRANS	0x01
 #define L2CAP_MODE_FLOWCTL	0x02
 #define L2CAP_MODE_ERTM		0x03
-#define L2CAP_MODE_STREAM	0x04
+#define L2CAP_MODE_STREAMING	0x04
 
 struct l2cap_disconn_req {
 	__le16     dcid;
@@ -271,6 +271,8 @@ struct l2cap_pinfo {
 	__u16		imtu;
 	__u16		omtu;
 	__u16		flush_to;
+	__u8		mode;
+	__u8		fcs;
 	__u8		sec_level;
 	__u8		role_switch;
 	__u8		force_reliable;

net/bluetooth/l2cap.c

@@ -717,12 +717,16 @@ static void l2cap_sock_init(struct sock *sk, struct sock *parent)
 
 		pi->imtu = l2cap_pi(parent)->imtu;
 		pi->omtu = l2cap_pi(parent)->omtu;
+		pi->mode = l2cap_pi(parent)->mode;
+		pi->fcs  = l2cap_pi(parent)->fcs;
 		pi->sec_level = l2cap_pi(parent)->sec_level;
 		pi->role_switch = l2cap_pi(parent)->role_switch;
 		pi->force_reliable = l2cap_pi(parent)->force_reliable;
 	} else {
 		pi->imtu = L2CAP_DEFAULT_MTU;
 		pi->omtu = 0;
+		pi->mode = L2CAP_MODE_BASIC;
+		pi->fcs  = L2CAP_FCS_CRC16;
 		pi->sec_level = BT_SECURITY_LOW;
 		pi->role_switch = 0;
 		pi->force_reliable = 0;
@@ -958,6 +962,18 @@ static int l2cap_sock_connect(struct socket *sock, struct sockaddr *addr, int al
 		goto done;
 	}
 
+	switch (l2cap_pi(sk)->mode) {
+	case L2CAP_MODE_BASIC:
+		break;
+	case L2CAP_MODE_ERTM:
+		if (enable_ertm)
+			break;
+		/* fall through */
+	default:
+		err = -ENOTSUPP;
+		goto done;
+	}
+
 	switch (sk->sk_state) {
 	case BT_CONNECT:
 	case BT_CONNECT2:
@@ -1009,6 +1025,18 @@ static int l2cap_sock_listen(struct socket *sock, int backlog)
 		goto done;
 	}
 
+	switch (l2cap_pi(sk)->mode) {
+	case L2CAP_MODE_BASIC:
+		break;
+	case L2CAP_MODE_ERTM:
+		if (enable_ertm)
+			break;
+		/* fall through */
+	default:
+		err = -ENOTSUPP;
+		goto done;
+	}
+
 	if (!l2cap_pi(sk)->psm) {
 		bdaddr_t *src = &bt_sk(sk)->src;
 		u16 psm;
@@ -1259,7 +1287,7 @@ static int l2cap_sock_setsockopt_old(struct socket *sock, int optname, char __us
 		opts.imtu     = l2cap_pi(sk)->imtu;
 		opts.omtu     = l2cap_pi(sk)->omtu;
 		opts.flush_to = l2cap_pi(sk)->flush_to;
-		opts.mode     = L2CAP_MODE_BASIC;
+		opts.mode     = l2cap_pi(sk)->mode;
 
 		len = min_t(unsigned int, sizeof(opts), optlen);
 		if (copy_from_user((char *) &opts, optval, len)) {
@@ -1269,6 +1297,7 @@ static int l2cap_sock_setsockopt_old(struct socket *sock, int optname, char __us
 
 		l2cap_pi(sk)->imtu = opts.imtu;
 		l2cap_pi(sk)->omtu = opts.omtu;
+		l2cap_pi(sk)->mode = opts.mode;
 		break;
 
 	case L2CAP_LM:
@@ -1381,7 +1410,7 @@ static int l2cap_sock_getsockopt_old(struct socket *sock, int optname, char __us
 		opts.imtu     = l2cap_pi(sk)->imtu;
 		opts.omtu     = l2cap_pi(sk)->omtu;
 		opts.flush_to = l2cap_pi(sk)->flush_to;
-		opts.mode     = L2CAP_MODE_BASIC;
+		opts.mode     = l2cap_pi(sk)->mode;
 
 		len = min_t(unsigned int, len, sizeof(opts));
 		if (copy_to_user(optval, (char *) &opts, len))