net: timestamp cloned packet in dev_queue_xmit_nit

Le vendredi 17 décembre 2010 à 10:26 +0100, Eric Dumazet a écrit :

>
> I think we can add this after latest Changli patch :
>
> He does one skb_clone() before calling the sniffers.
> We could set timestamp on this clone, instead of original skb.
>
> Problem solved.
>

[PATCH net-next-2.6] net: timestamp cloned packet in dev_queue_xmit_nit

Now we do one clone of skb if at least one sniffer might take packet,
we also can do the skb timestamping on the clone and let original packet
unchanged.

This is a generalization of commit 8caf1539 (net: sch_netem: Fix an
inconsistency in ingress netem timestamps.)

This way, we can have a good idea when packets are delivered to our
stack (tcpdump -i ifb0), while a tcpdump on original device gives
timestamps right before ingressing.

This also speedup our stack, avoiding taking timestamps if not needed.
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Cc: Changli Gao <xiaosuo@gmail.com>
Cc: Patrick McHardy <kaber@trash.net>
Cc: Jarek Poplawski <jarkao2@gmail.com>
Acked-by: NChangli Gao <xiaosuo@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -1547,13 +1547,6 @@ static void dev_queue_xmit_nit(struct sk_buff *skb, struct net_device *dev)
 	struct sk_buff *skb2 = NULL;
 	struct packet_type *pt_prev = NULL;
 
-#ifdef CONFIG_NET_CLS_ACT
-	if (!(skb->tstamp.tv64 && (G_TC_FROM(skb->tc_verd) & AT_INGRESS)))
-		net_timestamp_set(skb);
-#else
-	net_timestamp_set(skb);
-#endif
-
 	rcu_read_lock();
 	list_for_each_entry_rcu(ptype, &ptype_all, list) {
 		/* Never send packets back to the socket
@@ -1572,6 +1565,8 @@ static void dev_queue_xmit_nit(struct sk_buff *skb, struct net_device *dev)
 			if (!skb2)
 				break;
 
+			net_timestamp_set(skb2);
+
 			/* skb->nh should be correctly
 			   set by sender, so that the second statement is
 			   just protection against buggy protocols.