setting net.netfilter.nf_conntrack_timestamp=1 breaks xmit with fq
scheduler. skb->tstamp might be "refreshed" using ktime_get_real(),
but fq expects CLOCK_MONOTONIC.
This patch removes all places in netfilter that check/set skb->tstamp:
1. To fix the bogus "start" time seen with conntrack timestamping for
outgoing packets, never use skb->tstamp and always use current time.
2. In nfqueue and nflog, only use skb->tstamp for incoming packets,
as determined by current hook (prerouting, input, forward).
3. xt_time has to use system clock as well rather than skb->tstamp.
We could still use skb->tstamp for prerouting/input/foward, but
I see no advantage to make this conditional.
Fixes: fb420d5d91c1 ("tcp/fq: move back to CLOCK_MONOTONIC")
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Reported-by: Michal Soltys <soltys@xxxxxxxx>
Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
---
net/netfilter/nf_conntrack_core.c | 7 ++-----
net/netfilter/nfnetlink_log.c | 2 +-
net/netfilter/nfnetlink_queue.c | 2 +-
net/netfilter/xt_time.c | 23 ++++++++++++++---------
4 files changed, 18 insertions(+), 16 deletions(-)
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 3c48d44d6fff..2a714527cde1 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1017,12 +1017,9 @@ __nf_conntrack_confirm(struct sk_buff *skb)
/* set conntrack timestamp, if enabled. */
tstamp = nf_conn_tstamp_find(ct);
- if (tstamp) {
- if (skb->tstamp == 0)
- __net_timestamp(skb);
+ if (tstamp)
+ tstamp->start = ktime_get_real_ns();
- tstamp->start = ktime_to_ns(skb->tstamp);
- }
/* Since the lookup is lockless, hash insertion must be done after
* starting the timer and setting the CONFIRMED bit. The RCU barriers
* guarantee that no other CPU can find the conntrack before the above
diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index b1f9c5303f02..7d69a02bf016 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -540,7 +540,7 @@ __build_packet_message(struct nfnl_log_net *log,
goto nla_put_failure;
}
- if (skb->tstamp) {
+ if (hooknum <= NF_INET_FORWARD && skb->tstamp) {
struct nfulnl_msg_packet_timestamp ts;
struct timespec64 kts = ktime_to_timespec64(skb->tstamp);
ts.sec = cpu_to_be64(kts.tv_sec);
diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
index 0dcc3592d053..e057b2961d31 100644
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -582,7 +582,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
if (nfqnl_put_bridge(entry, skb) < 0)
goto nla_put_failure;
- if (entskb->tstamp) {
+ if (entry->state.hook <= NF_INET_FORWARD && entskb->tstamp) {
struct nfqnl_msg_packet_timestamp ts;
struct timespec64 kts = ktime_to_timespec64(entskb->tstamp);
diff --git a/net/netfilter/xt_time.c b/net/netfilter/xt_time.c
index c13bcd0ab491..8dbb4d48f2ed 100644
--- a/net/netfilter/xt_time.c
+++ b/net/netfilter/xt_time.c
@@ -163,19 +163,24 @@ time_mt(const struct sk_buff *skb, struct xt_action_param *par)
s64 stamp;
/*
- * We cannot use get_seconds() instead of __net_timestamp() here.
+ * We need real time here, but we can neither use skb->tstamp
+ * nor __net_timestamp().
+ *
+ * skb->tstamp and skb->skb_mstamp_ns overlap, however, they
+ * use different clock types (real vs monotonic).
+ *
* Suppose you have two rules:
- * 1. match before 13:00
- * 2. match after 13:00
+ * 1. match before 13:00
+ * 2. match after 13:00
+ *
* If you match against processing time (get_seconds) it
* may happen that the same packet matches both rules if
- * it arrived at the right moment before 13:00.
+ * it arrived at the right moment before 13:00, so it would be
+ * better to check skb->tstamp and set it via __net_timestamp()
+ * if needed. This however breaks outgoing packets tx timestamp,
+ * and causes them to get delayed forever by fq packet scheduler.
*/
- if (skb->tstamp == 0)
- __net_timestamp((struct sk_buff *)skb);
-
- stamp = ktime_to_ns(skb->tstamp);
- stamp = div_s64(stamp, NSEC_PER_SEC);
+ stamp = get_seconds();
if (info->flags & XT_TIME_LOCAL_TZ)
/* Adjust for local timezone */
--
2.21.0
