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net: Handle delivery_time in skb->tstamp during network tapping with af_packet

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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@ingress 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@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Martin KaFai Lau 2022-03-02 11:55:38 -08:00 committed by David S. Miller
parent de79910151
commit 27942a1520
3 changed files with 30 additions and 2 deletions
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24
include/linux/skbuff.h
View File

@ -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;

4
net/core/dev.c
View File

@ -2047,7 +2047,8 @@ 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;
@ -2108,6 +2109,7 @@ 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);
}

4
net/packet/af_packet.c
View File

@ -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);