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| author | Eric Dumazet <eric.dumazet@gmail.com> | 2011-05-23 11:02:42 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2011-05-23 17:36:00 -0400 |
| commit | 8efa885406359af300d46910642b50ca82c0fe47 (patch) | |
| tree | 1eecc0b8152d775b5c261a2a1749a2f711f81f13 /net | |
| parent | a4910b744486254cfa61995954c118fb2283c4fd (diff) | |
| download | blackbird-op-linux-8efa885406359af300d46910642b50ca82c0fe47.tar.gz blackbird-op-linux-8efa885406359af300d46910642b50ca82c0fe47.zip | |
sch_sfq: avoid giving spurious NET_XMIT_CN signals
While chasing a possible net_sched bug, I found that IP fragments have
litle chance to pass a congestioned SFQ qdisc :
- Say SFQ qdisc is full because one flow is non responsive.
- ip_fragment() wants to send two fragments belonging to an idle flow.
- sfq_enqueue() queues first packet, but see queue limit reached :
- sfq_enqueue() drops one packet from 'big consumer', and returns
NET_XMIT_CN.
- ip_fragment() cancel remaining fragments.
This patch restores fairness, making sure we return NET_XMIT_CN only if
we dropped a packet from the same flow.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Patrick McHardy <kaber@trash.net>
CC: Jarek Poplawski <jarkao2@gmail.com>
CC: Jamal Hadi Salim <hadi@cyberus.ca>
CC: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/sched/sch_sfq.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c index 7ef87f9eb675..b1d00f8e09f8 100644 --- a/net/sched/sch_sfq.c +++ b/net/sched/sch_sfq.c @@ -361,7 +361,7 @@ sfq_enqueue(struct sk_buff *skb, struct Qdisc *sch) { struct sfq_sched_data *q = qdisc_priv(sch); unsigned int hash; - sfq_index x; + sfq_index x, qlen; struct sfq_slot *slot; int uninitialized_var(ret); @@ -405,8 +405,12 @@ sfq_enqueue(struct sk_buff *skb, struct Qdisc *sch) if (++sch->q.qlen <= q->limit) return NET_XMIT_SUCCESS; + qlen = slot->qlen; sfq_drop(sch); - return NET_XMIT_CN; + /* Return Congestion Notification only if we dropped a packet + * from this flow. + */ + return (qlen != slot->qlen) ? NET_XMIT_CN : NET_XMIT_SUCCESS; } static struct sk_buff * |
