batman-adv: tp_meter: initialize dup_acks explicitly

When an ack with a sequence number equal to the last_acked is received, the
dup_acks counter is increased to decide whether fast retransmit should be
performed. Only when the sequence numbers are not equal, the dup_acks is
set to the initial value (0).

But if the initial packet would have the sequence number
BATADV_TP_FIRST_SEQ, dup_acks would not be initialized and atomic_inc would
operate on an undefined starting value. It is therefore required to have it
explicitly initialized during the start of the sender session.

Cc: stable@kernel.org
Fixes: 33a3bb4a33 ("batman-adv: throughput meter implementation")
Signed-off-by: Sven Eckelmann <sven@narfation.org>

net/batman-adv/tp_meter.c

@@ -1045,6 +1045,7 @@ void batadv_tp_start(struct batadv_priv *bat_priv, const u8 *dst,
 	tp_vars->icmp_uid = icmp_uid;
 
 	tp_vars->last_sent = BATADV_TP_FIRST_SEQ;
+	atomic_set(&tp_vars->dup_acks, 0);
 	atomic_set(&tp_vars->last_acked, BATADV_TP_FIRST_SEQ);
 	tp_vars->fast_recovery = false;
 	tp_vars->recover = BATADV_TP_FIRST_SEQ;