sch_sfq: fix sfq_enqueue()

commit 8efa88540635 (sch_sfq: avoid giving spurious NET_XMIT_CN signals)
forgot to call qdisc_tree_decrease_qlen() to signal upper levels that a
packet (from another flow) was dropped, leading to various problems.

With help from Michal Soltys and Michal Pokrywka, who did a bisection.

Bugzilla ref: https://bugzilla.kernel.org/show_bug.cgi?id=39372
Debian ref: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=631945

Reported-by: Lucas Bocchi <lucas.bocchi@gmail.com>
Reported-and-bisected-by: Michal Pokrywka <wolfmoon@o2.pl>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Michal Soltys <soltys@ziu.info>
Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 1 deletions

diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c
index 4536ee64383e..4f5510e2bd6f 100644
--- a/net/sched/sch_sfq.c
+++ b/net/sched/sch_sfq.c
@@ -410,7 +410,12 @@ sfq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
         /* Return Congestion Notification only if we dropped a packet
          * from this flow.
          */
-        return (qlen != slot->qlen) ? NET_XMIT_CN : NET_XMIT_SUCCESS;
+        if (qlen != slot->qlen)
+                return NET_XMIT_CN;
+
+        /* As we dropped a packet, better let upper stack know this */
+        qdisc_tree_decrease_qlen(sch, 1);
+        return NET_XMIT_SUCCESS;
 }
 
 static struct sk_buff *