Bluetooth: Add initial support for ERTM packets transfers

This patch adds support for ERTM transfers, without retransmission, with
txWindow up to 63 and with acknowledgement of packets received. Now the
packets are queued before call l2cap_do_send(), so packets couldn't be
sent at the time we call l2cap_sock_sendmsg(). They will be sent in
an asynchronous way on later calls of l2cap_ertm_send(). Besides if an
error occurs on calling l2cap_do_send() we disconnect the channel.

Initially based on a patch from Nathan Holstein <nathan@lampreynetworks.com>
Signed-off-by: Gustavo F. Padovan <gustavo@las.ic.unicamp.br>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

include/net/bluetooth/bluetooth.h

@@ -138,8 +138,9 @@ struct sock *bt_accept_dequeue(struct sock *parent, struct socket *newsock);
 struct bt_skb_cb {
 	__u8 pkt_type;
 	__u8 incoming;
+	__u8 tx_seq;
 };
-#define bt_cb(skb) ((struct bt_skb_cb *)(skb->cb)) 
+#define bt_cb(skb) ((struct bt_skb_cb *)((skb)->cb))
 
 static inline struct sk_buff *bt_skb_alloc(unsigned int len, gfp_t how)
 {

include/net/bluetooth/l2cap.h

@@ -29,7 +29,8 @@
 #define L2CAP_DEFAULT_MTU		672
 #define L2CAP_DEFAULT_MIN_MTU		48
 #define L2CAP_DEFAULT_FLUSH_TO		0xffff
-#define L2CAP_DEFAULT_TX_WINDOW		1
+#define L2CAP_DEFAULT_TX_WINDOW		63
+#define L2CAP_DEFAULT_NUM_TO_ACK        (L2CAP_DEFAULT_TX_WINDOW/5)
 #define L2CAP_DEFAULT_MAX_RECEIVE	1
 #define L2CAP_DEFAULT_RETRANS_TO	300    /* 300 milliseconds */
 #define L2CAP_DEFAULT_MONITOR_TO	1000   /* 1 second */
@@ -94,6 +95,31 @@ struct l2cap_conninfo {
 #define L2CAP_FCS_NONE		0x00
 #define L2CAP_FCS_CRC16		0x01
 
+/* L2CAP Control Field bit masks */
+#define L2CAP_CTRL_SAR               0xC000
+#define L2CAP_CTRL_REQSEQ            0x3F00
+#define L2CAP_CTRL_TXSEQ             0x007E
+#define L2CAP_CTRL_RETRANS           0x0080
+#define L2CAP_CTRL_FINAL             0x0080
+#define L2CAP_CTRL_POLL              0x0010
+#define L2CAP_CTRL_SUPERVISE         0x000C
+#define L2CAP_CTRL_FRAME_TYPE        0x0001 /* I- or S-Frame */
+
+#define L2CAP_CTRL_TXSEQ_SHIFT      1
+#define L2CAP_CTRL_REQSEQ_SHIFT     8
+
+/* L2CAP Supervisory Function */
+#define L2CAP_SUPER_RCV_READY           0x0000
+#define L2CAP_SUPER_REJECT              0x0004
+#define L2CAP_SUPER_RCV_NOT_READY       0x0008
+#define L2CAP_SUPER_SELECT_REJECT       0x000C
+
+/* L2CAP Segmentation and Reassembly */
+#define L2CAP_SDU_UNSEGMENTED       0x0000
+#define L2CAP_SDU_START             0x4000
+#define L2CAP_SDU_END               0x8000
+#define L2CAP_SDU_CONTINUE          0xC000
+
 /* L2CAP structures */
 struct l2cap_hdr {
 	__le16     len;
@@ -262,6 +288,7 @@ struct l2cap_conn {
 
 /* ----- L2CAP channel and socket info ----- */
 #define l2cap_pi(sk) ((struct l2cap_pinfo *) sk)
+#define TX_QUEUE(sk) (&l2cap_pi(sk)->tx_queue)
 
 struct l2cap_pinfo {
 	struct bt_sock	bt;
@@ -285,6 +312,13 @@ struct l2cap_pinfo {
 	__u8		conf_len;
 	__u8		conf_state;
 
+	__u8		next_tx_seq;
+	__u8		expected_ack_seq;
+	__u8		req_seq;
+	__u8		expected_tx_seq;
+	__u8		unacked_frames;
+	__u8		num_to_ack;
+
 	__u8		ident;
 
 	__u8		remote_tx_win;
@@ -295,6 +329,7 @@ struct l2cap_pinfo {
 
 	__le16		sport;
 
+	struct sk_buff_head	tx_queue;
 	struct l2cap_conn	*conn;
 	struct sock		*next_c;
 	struct sock		*prev_c;
@@ -311,6 +346,23 @@ struct l2cap_pinfo {
 #define L2CAP_CONF_MAX_CONF_REQ 2
 #define L2CAP_CONF_MAX_CONF_RSP 2
 
+static inline int l2cap_tx_window_full(struct sock *sk)
+{
+	struct l2cap_pinfo *pi = l2cap_pi(sk);
+	int sub;
+
+	sub = (pi->next_tx_seq - pi->expected_ack_seq) % 64;
+
+	if (sub < 0)
+		sub += 64;
+
+	return (sub == pi->remote_tx_win);
+}
+
+#define __get_txseq(ctrl) ((ctrl) & L2CAP_CTRL_TXSEQ) >> 1
+#define __get_reqseq(ctrl) ((ctrl) & L2CAP_CTRL_REQSEQ) >> 8
+#define __is_iframe(ctrl) !((ctrl) & L2CAP_CTRL_FRAME_TYPE)
+#define __is_sframe(ctrl) (ctrl) & L2CAP_CTRL_FRAME_TYPE
 
 void l2cap_load(void);