From 8caf153974f2274301e583fda732cc8e5b80331f Mon Sep 17 00:00:00 2001 From: Jarek Poplawski Date: Fri, 17 Apr 2009 10:08:49 +0000 Subject: [PATCH] net: sch_netem: Fix an inconsistency in ingress netem timestamps. Alex Sidorenko reported: "while experimenting with 'netem' we have found some strange behaviour. It seemed that ingress delay as measured by 'ping' command shows up on some hosts but not on others. After some investigation I have found that the problem is that skbuff->tstamp field value depends on whether there are any packet sniffers enabled. That is: - if any ptype_all handler is registered, the tstamp field is as expected - if there are no ptype_all handlers, the tstamp field does not show the delay" This patch prevents unnecessary update of tstamp in dev_queue_xmit_nit() on ingress path (with act_mirred) adding a check, so minimal overhead on the fast path, but only when sniffers etc. are active. Since netem at ingress seems to logically emulate a network before a host, tstamp is zeroed to trigger the update and pretend delays are from the outside. Reported-by: Alex Sidorenko Tested-by: Alex Sidorenko Signed-off-by: Jarek Poplawski Signed-off-by: David S. Miller --- net/core/dev.c | 5 +++++ net/sched/sch_netem.c | 8 ++++++++ 2 files changed, 13 insertions(+) diff --git a/net/core/dev.c b/net/core/dev.c index 343883f65ea7..dcc357e4f91e 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -1336,7 +1336,12 @@ static void dev_queue_xmit_nit(struct sk_buff *skb, struct net_device *dev) { struct packet_type *ptype; +#ifdef CONFIG_NET_CLS_ACT + if (!(skb->tstamp.tv64 && (G_TC_FROM(skb->tc_verd) & AT_INGRESS))) + net_timestamp(skb); +#else net_timestamp(skb); +#endif rcu_read_lock(); list_for_each_entry_rcu(ptype, &ptype_all, list) { diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index d876b8734848..2b88295cb7b7 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -280,6 +280,14 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch) if (unlikely(!skb)) return NULL; +#ifdef CONFIG_NET_CLS_ACT + /* + * If it's at ingress let's pretend the delay is + * from the network (tstamp will be updated). + */ + if (G_TC_FROM(skb->tc_verd) & AT_INGRESS) + skb->tstamp.tv64 = 0; +#endif pr_debug("netem_dequeue: return skb=%p\n", skb); sch->q.qlen--; return skb;