Bluetooth: Set P-bit for SREJ frame only if there are I-frames to ack

SREJ frame with P-bit set acknowledges I-frames numbered up to
(ReqSeq - 1). With this patch P-bit in SREJ is set only when there are
some I-frames to ack.

This fixes ambiguous situation when lost of I-frame with TxSeq=0 would
result in sending SREJ acking all previous I-frames.
Consider following scenario:
TxWindow=3

HostA: sent I-frame TxSeq=0
HostA: sent I-frame TxSeq=1
HostA: sent I-frame TxSeq=2
HostB: missed I-frame TxSeq=0
HostB: received I-frame TxSeq=1
HostB: sent SREJ ReqSeq=0 Pbit=1
HostA: received SREJ ReqSeq=0 Pbit=1   <- All I-frames acked or not?
...

Signed-off-by: Szymon Janc <szymon.janc@tieto.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index dcccae04ae086767c793b269fbcc7c0280a484b3..0d5bb45e7be756de15caa4e1ba827fb880bb0804 100644 (file)
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -3927,15 +3927,15 @@ static inline int l2cap_data_channel_iframe(struct l2cap_chan *chan, u32 rx_cont
                __skb_queue_head_init(&chan->srej_q);
                l2cap_add_to_srej_queue(chan, skb, tx_seq, sar);
 
-               set_bit(CONN_SEND_PBIT, &chan->conn_state);
+               /* Set P-bit only if there are some I-frames to ack. */
+               if (__clear_ack_timer(chan))
+                       set_bit(CONN_SEND_PBIT, &chan->conn_state);
 
                err = l2cap_send_srejframe(chan, tx_seq);
                if (err < 0) {
                        l2cap_send_disconn_req(chan->conn, chan, -err);
                        return err;
                }
-
-               __clear_ack_timer(chan);
        }
        return 0;