Bluetooth: Use non-flushable pb flag by default for ACL data on capable chipsets.

With Bluetooth 2.1 ACL packets can be flushable or non-flushable. This commit
makes ACL data packets non-flushable by default on compatible chipsets, and
adds the L2CAP_LM_FLUSHABLE socket option to explicitly request flushable ACL
data packets for a given L2CAP socket. This is useful for A2DP data which can
be safely discarded if it can not be delivered within a short time (while
other ACL data should not be discarded).

Note that making ACL data flushable has no effect unless the automatic flush
timeout for that ACL link is changed from its default of 0 (infinite).

Change-Id: Ie3d4befdeaefb8c979de7ae603ff5ec462b3483c
Signed-off-by: Nick Pelly <npelly@google.com>

2 files changed, 26 insertions, 5 deletions

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index c52f091ee6de..a49aa2bf97f3 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -1367,7 +1367,7 @@ void hci_send_acl(struct hci_conn *conn, struct sk_buff *skb, __u16 flags)
 
 	skb->dev = (void *) hdev;
 	bt_cb(skb)->pkt_type = HCI_ACLDATA_PKT;
-	hci_add_acl_hdr(skb, conn->handle, flags | ACL_START);
+	hci_add_acl_hdr(skb, conn->handle, flags);
 
 	if (!(list = skb_shinfo(skb)->frag_list)) {
 		/* Non fragmented */
@@ -1384,12 +1384,14 @@ void hci_send_acl(struct hci_conn *conn, struct sk_buff *skb, __u16 flags)
 		spin_lock_bh(&conn->data_q.lock);
 
 		__skb_queue_tail(&conn->data_q, skb);
+		flags &= ~ACL_PB_MASK;
+		flags |= ACL_CONT;
 		do {
 			skb = list; list = list->next;
 
 			skb->dev = (void *) hdev;
 			bt_cb(skb)->pkt_type = HCI_ACLDATA_PKT;
-			hci_add_acl_hdr(skb, conn->handle, flags | ACL_CONT);
+			hci_add_acl_hdr(skb, conn->handle, flags);
 
 			BT_DBG("%s frag %p len %d", hdev->name, skb, skb->len);
 
diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
index 001a638fe2c0..0ac962b978e1 100644
--- a/net/bluetooth/l2cap.c
+++ b/net/bluetooth/l2cap.c
@@ -354,13 +354,19 @@ static inline u8 l2cap_get_ident(struct l2cap_conn *conn)
 static inline void l2cap_send_cmd(struct l2cap_conn *conn, u8 ident, u8 code, u16 len, void *data)
 {
 	struct sk_buff *skb = l2cap_build_cmd(conn, code, ident, len, data);
+	u8 flags;
 
 	BT_DBG("code 0x%2.2x", code);
 
 	if (!skb)
 		return;
 
-	hci_send_acl(conn->hcon, skb, 0);
+	if (lmp_no_flush_capable(conn->hcon->hdev))
+		flags = ACL_START_NO_FLUSH;
+	else
+		flags = ACL_START;
+
+	hci_send_acl(conn->hcon, skb, flags);
 }
 
 static inline void l2cap_send_sframe(struct l2cap_pinfo *pi, u16 control)
@@ -900,6 +906,7 @@ static void l2cap_sock_init(struct sock *sk, struct sock *parent)
 		pi->sec_level = l2cap_pi(parent)->sec_level;
 		pi->role_switch = l2cap_pi(parent)->role_switch;
 		pi->force_reliable = l2cap_pi(parent)->force_reliable;
+		pi->flushable = l2cap_pi(parent)->flushable;
 	} else {
 		pi->imtu = L2CAP_DEFAULT_MTU;
 		pi->omtu = 0;
@@ -915,6 +922,7 @@ static void l2cap_sock_init(struct sock *sk, struct sock *parent)
 		pi->sec_level = BT_SECURITY_LOW;
 		pi->role_switch = 0;
 		pi->force_reliable = 0;
+		pi->flushable = 0;
 	}
 
 	/* Default config options */
@@ -1433,10 +1441,17 @@ static void l2cap_drop_acked_frames(struct sock *sk)
 static inline void l2cap_do_send(struct sock *sk, struct sk_buff *skb)
 {
 	struct l2cap_pinfo *pi = l2cap_pi(sk);
+	struct hci_conn *hcon = pi->conn->hcon;
+	u16 flags;
 
 	BT_DBG("sk %p, skb %p len %d", sk, skb, skb->len);
 
-	hci_send_acl(pi->conn->hcon, skb, 0);
+	if (lmp_no_flush_capable(hcon->hdev) && !l2cap_pi(sk)->flushable)
+		flags = ACL_START_NO_FLUSH;
+	else
+		flags = ACL_START;
+
+	hci_send_acl(hcon, skb, flags);
 }
 
 static void l2cap_streaming_send(struct sock *sk)
@@ -2016,6 +2031,7 @@ static int l2cap_sock_setsockopt_old(struct socket *sock, int optname, char __us
 
 		l2cap_pi(sk)->role_switch    = (opt & L2CAP_LM_MASTER);
 		l2cap_pi(sk)->force_reliable = (opt & L2CAP_LM_RELIABLE);
+		l2cap_pi(sk)->flushable = (opt & L2CAP_LM_FLUSHABLE);
 		break;
 
 	default:
@@ -2146,6 +2162,9 @@ static int l2cap_sock_getsockopt_old(struct socket *sock, int optname, char __us
 		if (l2cap_pi(sk)->force_reliable)
 			opt |= L2CAP_LM_RELIABLE;
 
+		if (l2cap_pi(sk)->flushable)
+			opt |= L2CAP_LM_FLUSHABLE;
+
 		if (put_user(opt, (u32 __user *) optval))
 			err = -EFAULT;
 		break;
@@ -4645,7 +4664,7 @@ static int l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 fl
 
 	BT_DBG("conn %p len %d flags 0x%x", conn, skb->len, flags);
 
-	if (flags & ACL_START) {
+	if (!(flags & ACL_CONT)) {
 		struct l2cap_hdr *hdr;
 		int len;