commit fe7b307ab374a495feba8c951fb7da2518a4e422
Author: Christopher Zimmermann <madroach@zakweb.de>
Date:   Sat Sep 19 19:21:28 2009 +0200

    net: Implement timestamping
    
    Avoid the skb_clone, skb_hold and software fallback problems by
    returning two seperate messages to userspace. One for software and one
    for hardware timestamp.

diff --git a/drivers/net/igb/igb_main.c b/drivers/net/igb/igb_main.c
index d2639c4..1bdce95 100644
--- a/drivers/net/igb/igb_main.c
+++ b/drivers/net/igb/igb_main.c
@@ -4435,7 +4435,7 @@ static void igb_tx_hwtstamp(struct igb_adapter *adapter, struct sk_buff *skb)
 			shhwtstamps.hwtstamp = ns_to_ktime(ns);
 			shhwtstamps.syststamp =
 				timecompare_transform(&adapter->compare, ns);
-			skb_tstamp_tx(skb, &shhwtstamps);
+			skb_tstamp_hw_tx(skb, &shhwtstamps);
 		}
 	}
 }
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index df7b23a..315a4c4 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1868,7 +1868,7 @@ static inline ktime_t net_invalid_timestamp(void)
 }
 
 /**
- * skb_tstamp_tx - queue clone of skb with send time stamps
+ * skb_tstamp_tx - queue clone of skb with hardware send time stamps
  * @orig_skb:	the original outgoing packet
  * @hwtstamps:	hardware time stamps, may be NULL if not available
  *
@@ -1878,9 +1878,21 @@ static inline ktime_t net_invalid_timestamp(void)
  * generates a software time stamp (otherwise), then queues the clone
  * to the error queue of the socket.  Errors are silently ignored.
  */
-extern void skb_tstamp_tx(struct sk_buff *orig_skb,
+extern void skb_tstamp_hw_tx(struct sk_buff *orig_skb,
 			struct skb_shared_hwtstamps *hwtstamps);
 
+/**
+ * skb_tstamp_tx - queue clone of skb with software generated send time stamps
+ * @orig_skb:	the original outgoing packet
+ *
+ * If the skb has a socket associated, then this function clones the
+ * skb (thus sharing the actual data and optional structures), generates a
+ * software time stamp, then queues the clone to the error queue of the socket.
+ * Errors are silently ignored.
+ */
+extern void skb_tstamp_tx(struct sk_buff *skb);
+			
+
 extern __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len);
 extern __sum16 __skb_checksum_complete(struct sk_buff *skb);
 
diff --git a/net/core/dev.c b/net/core/dev.c
index 560c8c9..c04d3dd 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1701,6 +1701,16 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
 {
 	const struct net_device_ops *ops = dev->netdev_ops;
 	int rc;
+	struct sk_buff *skb_tstamp = NULL;
+
+	if (unlikely(skb_tx(skb)->software && skb->sk)) {
+		skb_tstamp = skb_clone(skb, 0);
+
+		/* TODO: Is a sock_hold() needed here?
+		 * skb_set_owner_w doesn't do it. */
+		if (likely(skb_tstamp))
+		    	skb_set_owner_w(skb_tstamp, skb->sk);
+	}
 
 	if (likely(!skb->next)) {
 		if (!list_empty(&ptype_all))
@@ -1721,8 +1731,11 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
 			skb_dst_drop(skb);
 
 		rc = ops->ndo_start_xmit(skb, dev);
-		if (rc == NETDEV_TX_OK)
+		if (rc == NETDEV_TX_OK) {
+			if (unlikely(skb_tstamp))
+				skb_tstamp_tx(skb_tstamp);
 			txq_trans_update(txq);
+		}
 		/*
 		 * TODO: if skb_orphan() was called by
 		 * dev->hard_start_xmit() (for example, the unmodified
@@ -1752,6 +1765,8 @@ gso:
 			skb->next = nskb;
 			return rc;
 		}
+		if (unlikely(skb_tstamp))
+			skb_tstamp_tx(skb_tstamp);
 		txq_trans_update(txq);
 		if (unlikely(netif_tx_queue_stopped(txq) && skb->next))
 			return NETDEV_TX_BUSY;
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 80a9616..1517a5e 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2967,7 +2967,7 @@ int skb_cow_data(struct sk_buff *skb, int tailbits, struct sk_buff **trailer)
 }
 EXPORT_SYMBOL_GPL(skb_cow_data);
 
-void skb_tstamp_tx(struct sk_buff *orig_skb,
+void skb_tstamp_hw_tx(struct sk_buff *orig_skb,
 		struct skb_shared_hwtstamps *hwtstamps)
 {
 	struct sock *sk = orig_skb->sk;
@@ -2982,17 +2982,9 @@ void skb_tstamp_tx(struct sk_buff *orig_skb,
 	if (!skb)
 		return;
 
-	if (hwtstamps) {
+	if (hwtstamps)
 		*skb_hwtstamps(skb) =
 			*hwtstamps;
-	} else {
-		/*
-		 * no hardware time stamps available,
-		 * so keep the skb_shared_tx and only
-		 * store software time stamp
-		 */
-		skb->tstamp = ktime_get_real();
-	}
 
 	serr = SKB_EXT_ERR(skb);
 	memset(serr, 0, sizeof(*serr));
@@ -3002,6 +2994,23 @@ void skb_tstamp_tx(struct sk_buff *orig_skb,
 	if (err)
 		kfree_skb(skb);
 }
+EXPORT_SYMBOL_GPL(skb_tstamp_hw_tx);
+
+void skb_tstamp_tx(struct sk_buff *skb)
+{
+	struct sock_exterr_skb *serr;
+	int err;
+
+	skb->tstamp = ktime_get_real();
+
+	serr = SKB_EXT_ERR(skb);
+	memset(serr, 0, sizeof(*serr));
+	serr->ee.ee_errno = ENOMSG;
+	serr->ee.ee_origin = SO_EE_ORIGIN_TIMESTAMPING;
+	err = sock_queue_err_skb(skb->sk, skb);
+	if (err)
+		kfree_skb(skb);
+}
 EXPORT_SYMBOL_GPL(skb_tstamp_tx);