[PATCH net] act_mirred: clear skb->tstamp on redirect

[PATCH net] act_mirred: clear skb->tstamp on redirect

[Eric Dumazet]

If sch_fq is used at ingress, skbs that might have been
timestamped by net_timestamp_set() if a packet capture
is requesting timestamps could be delayed by arbitrary
amount of time, since sch_fq time base is MONOTONIC.

Fix this problem by moving code from sch_netem.c to act_mirred.c.

Fixes: fb420d5d91c1 ("tcp/fq: move back to CLOCK_MONOTONIC")
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/sched/act_mirred.c | 3 ++-
 net/sched/sch_netem.c  | 9 ---------
 2 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
index 1dae5f2b358fcf3dac2bbc0ef80f53b0dba16c91..c8cf4d10c4355f934c02d407ec725670e36433b8 100644
--- a/net/sched/act_mirred.c
+++ b/net/sched/act_mirred.c
@@ -258,7 +258,8 @@ static int tcf_mirred_act(struct sk_buff *skb, const struct tc_action *a,
 	if (is_redirect) {
 		skb2->tc_redirected = 1;
 		skb2->tc_from_ingress = skb2->tc_at_ingress;
-
+		if (skb2->tc_from_ingress)
+			skb2->tstamp = 0;
 		/* let's the caller reinsert the packet, if possible */
 		if (use_reinsert) {
 			res->ingress = want_ingress;
diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 57b3ad9394ad7a9f42c48d7645a61a6a03b2efe0..2c38e3d0792468162ee0dc4137f1400160ab9276 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -648,15 +648,6 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch)
 			 */
 			skb->dev = qdisc_dev(sch);
 
-#ifdef CONFIG_NET_CLS_ACT
-			/*
-			 * If it's at ingress let's pretend the delay is
-			 * from the network (tstamp will be updated).
-			 */
-			if (skb->tc_redirected && skb->tc_from_ingress)
-				skb->tstamp = 0;
-#endif
-
 			if (q->slot.slot_next) {
 				q->slot.packets_left--;
 				q->slot.bytes_left -= qdisc_pkt_len(skb);
-- 
2.19.1.930.g4563a0d9d0-goog

Re: [PATCH net] act_mirred: clear skb->tstamp on redirect

[David Miller]

From: Eric Dumazet <edumazet@google.com>
Date: Sat, 10 Nov 2018 16:22:29 -0800

> If sch_fq is used at ingress, skbs that might have been
> timestamped by net_timestamp_set() if a packet capture
> is requesting timestamps could be delayed by arbitrary
> amount of time, since sch_fq time base is MONOTONIC.
> 
> Fix this problem by moving code from sch_netem.c to act_mirred.c.
> 
> Fixes: fb420d5d91c1 ("tcp/fq: move back to CLOCK_MONOTONIC")
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Applied.