[PATCH batadv v6 06/11] batman-adv: tp_meter: fix fast recovery precondition

Sven Eckelmann <[email protected]>
Newsgroups org.open-mesh.lists.batman
Message-ID <[email protected]>
The fast recovery precondition checks if the recover (initialized to
BATADV_TP_FIRST_SEQ) is bigger than the received ack. But since recover is
only updated when this check is successful, it will never enter the fast
recovery mode.

According to RFC6582 Section 3.2 step 2, the check should actually be
different:

> When the third duplicate ACK is received, the TCP sender first
> checks the value of recover to see if the Cumulative
> Acknowledgment field covers more than recover

The precondition must therefore check if recover is smaller than the
received ack - basically swapping the operands of the current check.

Fixes: 98d7a766b645 ("batman-adv: throughput meter implementation")
Signed-off-by: Sven Eckelmann <[email protected]>
---
 net/batman-adv/tp_meter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/batman-adv/tp_meter.c b/net/batman-adv/tp_meter.c
index 7760ace7..72ff3526 100644
--- a/net/batman-adv/tp_meter.c
+++ b/net/batman-adv/tp_meter.c
@@ -733,7 +733,7 @@ static void batadv_tp_recv_ack(struct batadv_priv *bat_priv,
 		if (atomic_read(&tp_vars->dup_acks) != 3)
 			goto out;
 
-		if (recv_ack >= tp_vars->recover)
+		if (tp_vars->recover >= recv_ack)
 			goto out;
 
 		/* if this is the third duplicate ACK do Fast Retransmit */

-- 
2.47.3
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