sch_sfq: avoid giving spurious NET_XMIT_CN signals
commit8efa885406359af300d46910642b50ca82c0fe47
authorEric Dumazet <eric.dumazet@gmail.com>
Mon, 23 May 2011 11:02:42 +0000 (23 11:02 +0000)
committerDavid S. Miller <davem@davemloft.net>
Mon, 23 May 2011 21:36:00 +0000 (23 17:36 -0400)
tree1eecc0b8152d775b5c261a2a1749a2f711f81f13
parenta4910b744486254cfa61995954c118fb2283c4fd
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>
net/sched/sch_sfq.c