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Message-ID: <20220302195538.3480753-1-kafai@fb.com>
Date: Wed, 2 Mar 2022 11:55:38 -0800
From: Martin KaFai Lau <kafai@...com>
To: <bpf@...r.kernel.org>, <netdev@...r.kernel.org>
CC: Alexei Starovoitov <ast@...nel.org>,
Andrii Nakryiko <andrii@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
David Miller <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, <kernel-team@...com>,
Willem de Bruijn <willemb@...gle.com>
Subject: [PATCH v6 net-next 03/13] net: Handle delivery_time in skb->tstamp during network tapping with af_packet
A latter patch will set the skb->mono_delivery_time to flag the skb->tstamp
is used as the mono delivery_time (EDT) instead of the (rcv) timestamp.
skb_clear_tstamp() will then keep this delivery_time during forwarding.
This patch is to make the network tapping (with af_packet) to handle
the delivery_time stored in skb->tstamp.
Regardless of tapping at the ingress or egress, the tapped skb is
received by the af_packet socket, so it is ingress to the af_packet
socket and it expects the (rcv) timestamp.
When tapping at egress, dev_queue_xmit_nit() is used. It has already
expected skb->tstamp may have delivery_time, so it does
skb_clone()+net_timestamp_set() to ensure the cloned skb has
the (rcv) timestamp before passing to the af_packet sk.
This patch only adds to clear the skb->mono_delivery_time
bit in net_timestamp_set().
When tapping at ingress, it currently expects the skb->tstamp is either 0
or the (rcv) timestamp. Meaning, the tapping at ingress path
has already expected the skb->tstamp could be 0 and it will get
the (rcv) timestamp by ktime_get_real() when needed.
There are two cases for tapping at ingress:
One case is af_packet queues the skb to its sk_receive_queue.
The skb is either not shared or new clone created. The newly
added skb_clear_delivery_time() is called to clear the
delivery_time (if any) and set the (rcv) timestamp if
needed before the skb is queued to the sk_receive_queue.
Another case, the ingress skb is directly copied to the rx_ring
and tpacket_get_timestamp() is used to get the (rcv) timestamp.
The newly added skb_tstamp() is used in tpacket_get_timestamp()
to check the skb->mono_delivery_time bit before returning skb->tstamp.
As mentioned earlier, the tapping@...ress has already expected
the skb may not have the (rcv) timestamp (because no sk has asked
for it) and has handled this case by directly calling ktime_get_real().
Signed-off-by: Martin KaFai Lau <kafai@...com>
---
include/linux/skbuff.h | 24 ++++++++++++++++++++++++
net/core/dev.c | 4 +++-
net/packet/af_packet.c | 4 +++-
3 files changed, 30 insertions(+), 2 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 27a28920e7b3..7e2d796ece80 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3996,6 +3996,22 @@ static inline void skb_set_delivery_time(struct sk_buff *skb, ktime_t kt,
skb->mono_delivery_time = 0;
}
+DECLARE_STATIC_KEY_FALSE(netstamp_needed_key);
+
+/* It is used in the ingress path to clear the delivery_time.
+ * If needed, set the skb->tstamp to the (rcv) timestamp.
+ */
+static inline void skb_clear_delivery_time(struct sk_buff *skb)
+{
+ if (skb->mono_delivery_time) {
+ skb->mono_delivery_time = 0;
+ if (static_branch_unlikely(&netstamp_needed_key))
+ skb->tstamp = ktime_get_real();
+ else
+ skb->tstamp = 0;
+ }
+}
+
static inline void skb_clear_tstamp(struct sk_buff *skb)
{
if (skb->mono_delivery_time)
@@ -4004,6 +4020,14 @@ static inline void skb_clear_tstamp(struct sk_buff *skb)
skb->tstamp = 0;
}
+static inline ktime_t skb_tstamp(const struct sk_buff *skb)
+{
+ if (skb->mono_delivery_time)
+ return 0;
+
+ return skb->tstamp;
+}
+
static inline u8 skb_metadata_len(const struct sk_buff *skb)
{
return skb_shinfo(skb)->meta_len;
diff --git a/net/core/dev.c b/net/core/dev.c
index 2d6771075720..6d81b5a7ef3f 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2020,7 +2020,8 @@ void net_dec_egress_queue(void)
EXPORT_SYMBOL_GPL(net_dec_egress_queue);
#endif
-static DEFINE_STATIC_KEY_FALSE(netstamp_needed_key);
+DEFINE_STATIC_KEY_FALSE(netstamp_needed_key);
+EXPORT_SYMBOL(netstamp_needed_key);
#ifdef CONFIG_JUMP_LABEL
static atomic_t netstamp_needed_deferred;
static atomic_t netstamp_wanted;
@@ -2081,6 +2082,7 @@ EXPORT_SYMBOL(net_disable_timestamp);
static inline void net_timestamp_set(struct sk_buff *skb)
{
skb->tstamp = 0;
+ skb->mono_delivery_time = 0;
if (static_branch_unlikely(&netstamp_needed_key))
__net_timestamp(skb);
}
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index ab87f22cc7ec..1b93ce1a5600 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -460,7 +460,7 @@ static __u32 tpacket_get_timestamp(struct sk_buff *skb, struct timespec64 *ts,
return TP_STATUS_TS_RAW_HARDWARE;
if ((flags & SOF_TIMESTAMPING_SOFTWARE) &&
- ktime_to_timespec64_cond(skb->tstamp, ts))
+ ktime_to_timespec64_cond(skb_tstamp(skb), ts))
return TP_STATUS_TS_SOFTWARE;
return 0;
@@ -2199,6 +2199,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
spin_lock(&sk->sk_receive_queue.lock);
po->stats.stats1.tp_packets++;
sock_skb_set_dropcount(sk, skb);
+ skb_clear_delivery_time(skb);
__skb_queue_tail(&sk->sk_receive_queue, skb);
spin_unlock(&sk->sk_receive_queue.lock);
sk->sk_data_ready(sk);
@@ -2377,6 +2378,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
po->stats.stats1.tp_packets++;
if (copy_skb) {
status |= TP_STATUS_COPY;
+ skb_clear_delivery_time(copy_skb);
__skb_queue_tail(&sk->sk_receive_queue, copy_skb);
}
spin_unlock(&sk->sk_receive_queue.lock);
--
2.30.2
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