[Bluetooth] Disable credit based flow control by default

The credit based flow control must be disabled by default for compatibility
with Bluetooth 1.0b devices. This patch makes CFC a session attribute,
introduces CFC states and cleans up the CFC logic.

include/net/bluetooth/rfcomm.h

@@ -167,8 +167,8 @@ struct rfcomm_session {
 	int              initiator;
 
 	/* Default DLC parameters */
+	int    cfc;
 	uint   mtu;
-	uint   credits;
 
 	struct list_head dlcs;
 };
@@ -190,7 +190,7 @@ struct rfcomm_dlc {
 	u8            mscex;
 
 	uint          mtu;
-	uint          credits;
+	uint          cfc;
 	uint          rx_credits;
 	uint          tx_credits;
 
@@ -219,6 +219,11 @@ struct rfcomm_dlc {
 #define RFCOMM_MSCEX_RX     2
 #define RFCOMM_MSCEX_OK     (RFCOMM_MSCEX_TX + RFCOMM_MSCEX_RX)
 
+/* CFC states */
+#define RFCOMM_CFC_UNKNOWN  -1
+#define RFCOMM_CFC_DISABLED 0
+#define RFCOMM_CFC_ENABLED  RFCOMM_MAX_CREDITS
+
 extern struct task_struct *rfcomm_thread;
 extern unsigned long rfcomm_event;
 

net/bluetooth/rfcomm/core.c

@@ -52,7 +52,7 @@
 #include <net/bluetooth/l2cap.h>
 #include <net/bluetooth/rfcomm.h>
 
-#define VERSION "1.0"
+#define VERSION "1.1"
 
 #ifndef CONFIG_BT_RFCOMM_DEBUG
 #undef  BT_DBG
@@ -207,7 +207,7 @@ static void rfcomm_dlc_clear_state(struct rfcomm_dlc *d)
 	d->mtu        = RFCOMM_DEFAULT_MTU;
 	d->v24_sig    = RFCOMM_V24_RTC | RFCOMM_V24_RTR | RFCOMM_V24_DV;
 
-	d->credits    = RFCOMM_MAX_CREDITS;
+	d->cfc        = RFCOMM_CFC_DISABLED;
 	d->rx_credits = RFCOMM_DEFAULT_CREDITS;
 }
 
@@ -315,7 +315,7 @@ static int __rfcomm_dlc_open(struct rfcomm_dlc *d, bdaddr_t *src, bdaddr_t *dst,
 	rfcomm_dlc_link(s, d);
 
 	d->mtu = s->mtu;
-	d->credits = s->credits;
+	d->cfc = (s->cfc == RFCOMM_CFC_UNKNOWN) ? 0 : s->cfc;
 
 	if (s->state == BT_CONNECTED)
 		rfcomm_send_pn(s, 1, d);
@@ -415,7 +415,7 @@ void __rfcomm_dlc_throttle(struct rfcomm_dlc *d)
 {
 	BT_DBG("dlc %p state %ld", d, d->state);
 
-	if (!d->credits) {
+	if (!d->cfc) {
 		d->v24_sig |= RFCOMM_V24_FC;
 		set_bit(RFCOMM_MSC_PENDING, &d->flags);
 	}
@@ -426,7 +426,7 @@ void __rfcomm_dlc_unthrottle(struct rfcomm_dlc *d)
 {
 	BT_DBG("dlc %p state %ld", d, d->state);
 
-	if (!d->credits) {
+	if (!d->cfc) {
 		d->v24_sig &= ~RFCOMM_V24_FC;
 		set_bit(RFCOMM_MSC_PENDING, &d->flags);
 	}
@@ -480,7 +480,7 @@ struct rfcomm_session *rfcomm_session_add(struct socket *sock, int state)
 	s->sock  = sock;
 
 	s->mtu   = RFCOMM_DEFAULT_MTU;
-	s->credits = RFCOMM_MAX_CREDITS;
+	s->cfc   = RFCOMM_CFC_UNKNOWN;
 	
 	list_add(&s->list, &session_list);
 
@@ -752,7 +752,7 @@ static int rfcomm_send_pn(struct rfcomm_session *s, int cr, struct rfcomm_dlc *d
 	pn->ack_timer   = 0;
 	pn->max_retrans = 0;
 
-	if (d->credits) {
+	if (s->cfc) {
 		pn->flow_ctrl = cr ? 0xf0 : 0xe0;
 		pn->credits = RFCOMM_DEFAULT_CREDITS;
 	} else {
@@ -1142,28 +1142,22 @@ static int rfcomm_recv_sabm(struct rfcomm_session *s, u8 dlci)
 
 static int rfcomm_apply_pn(struct rfcomm_dlc *d, int cr, struct rfcomm_pn *pn)
 {
+	struct rfcomm_session *s = d->session;
+
 	BT_DBG("dlc %p state %ld dlci %d mtu %d fc 0x%x credits %d", 
 			d, d->state, d->dlci, pn->mtu, pn->flow_ctrl, pn->credits);
 
-	if (cr) {
-		if (pn->flow_ctrl == 0xf0) {
+	if (pn->flow_ctrl == 0xf0 || pn->flow_ctrl == 0xe0) {
+		d->cfc = s->cfc = RFCOMM_CFC_ENABLED;
 		d->tx_credits = pn->credits;
 	} else {
+		d->cfc = s->cfc = RFCOMM_CFC_DISABLED;
 		set_bit(RFCOMM_TX_THROTTLED, &d->flags);
-			d->credits = 0;
-		}
-	} else {
-		if (pn->flow_ctrl == 0xe0) {
-			d->tx_credits = pn->credits;
-		} else {
-			set_bit(RFCOMM_TX_THROTTLED, &d->flags);
-			d->credits = 0;
-		}
 	}
 
 	d->priority = pn->priority;
 
-	d->mtu = btohs(pn->mtu);
+	d->mtu = s->mtu = btohs(pn->mtu);
 
 	return 0;
 }
@@ -1353,7 +1347,7 @@ static int rfcomm_recv_msc(struct rfcomm_session *s, int cr, struct sk_buff *skb
 		return 0;
 
 	if (cr) {
-		if (msc->v24_sig & RFCOMM_V24_FC && !d->credits)
+		if (msc->v24_sig & RFCOMM_V24_FC && !d->cfc)
 			set_bit(RFCOMM_TX_THROTTLED, &d->flags);
 		else
 			clear_bit(RFCOMM_TX_THROTTLED, &d->flags);
@@ -1444,7 +1438,7 @@ static int rfcomm_recv_data(struct rfcomm_session *s, u8 dlci, int pf, struct sk
 		goto drop;
 	}
 
-	if (pf && d->credits) {
+	if (pf && d->cfc) {
 		u8 credits = *(u8 *) skb->data; skb_pull(skb, 1);
 
 		d->tx_credits += credits;
@@ -1549,20 +1543,20 @@ static inline int rfcomm_process_tx(struct rfcomm_dlc *d)
 	struct sk_buff *skb;
 	int err;
 
-	BT_DBG("dlc %p state %ld credits %d rx_credits %d tx_credits %d", 
-			d, d->state, d->credits, d->rx_credits, d->tx_credits);
+	BT_DBG("dlc %p state %ld cfc %d rx_credits %d tx_credits %d", 
+			d, d->state, d->cfc, d->rx_credits, d->tx_credits);
 
 	/* Send pending MSC */
 	if (test_and_clear_bit(RFCOMM_MSC_PENDING, &d->flags))
 		rfcomm_send_msc(d->session, 1, d->dlci, d->v24_sig); 
 	
-	if (d->credits) {
+	if (d->cfc) {
 		/* CFC enabled. 
 		 * Give them some credits */
 		if (!test_bit(RFCOMM_RX_THROTTLED, &d->flags) &&
-			       	d->rx_credits <= (d->credits >> 2)) {
-			rfcomm_send_credits(d->session, d->addr, d->credits - d->rx_credits);
-			d->rx_credits = d->credits;
+			       	d->rx_credits <= (d->cfc >> 2)) {
+			rfcomm_send_credits(d->session, d->addr, d->cfc - d->rx_credits);
+			d->rx_credits = d->cfc;
 		}
 	} else {
 		/* CFC disabled.
@@ -1583,7 +1577,7 @@ static inline int rfcomm_process_tx(struct rfcomm_dlc *d)
 		d->tx_credits--;
 	}
 
-	if (d->credits && !d->tx_credits) {
+	if (d->cfc && !d->tx_credits) {
 		/* We're out of TX credits.
 		 * Set TX_THROTTLED flag to avoid unnesary wakeups by dlc_send. */
 		set_bit(RFCOMM_TX_THROTTLED, &d->flags);