path: root/net/packet/af_packet.c
diff options
authorMartin KaFai Lau <>2022-03-02 11:55:38 -0800
committerDavid S. Miller <>2022-03-03 14:38:48 +0000
commit27942a15209f564ed8ee2a9e126cb7b105181355 (patch)
treee6ef34b008fa969dd0fbc371c5dec3999cc409e1 /net/packet/af_packet.c
parentde799101519aad23c6096041ba2744d7b5517e6a (diff)
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@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 <> Signed-off-by: David S. Miller <>
Diffstat (limited to 'net/packet/af_packet.c')
1 files changed, 3 insertions, 1 deletions
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,
- ktime_to_timespec64_cond(skb->tstamp, ts))
+ ktime_to_timespec64_cond(skb_tstamp(skb), ts))
return 0;
@@ -2199,6 +2199,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
sock_skb_set_dropcount(sk, skb);
+ skb_clear_delivery_time(skb);
__skb_queue_tail(&sk->sk_receive_queue, skb);
@@ -2377,6 +2378,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
if (copy_skb) {
status |= TP_STATUS_COPY;
+ skb_clear_delivery_time(copy_skb);
__skb_queue_tail(&sk->sk_receive_queue, copy_skb);