net-timestamp: Make the clone operation stand-alone from phy timestamping

The phy timestamping takes a different path than the regular timestamping
does in that it will create a clone first so that the packets needing to be
timestamped can be placed in a queue, or the context block could be used.

In order to support these use cases I am pulling the core of the code out
so it can be used in other drivers beyond just phy devices.

In addition I have added a destructor named sock_efree which is meant to
provide a simple way for dropping the reference to skb exceptions that
aren't part of either the receive or send windows for the socket, and I
have removed some duplication in spots where this destructor could be used
in place of sock_edemux.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 25 insertions, 7 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 697e696..a936a40 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3511,6 +3511,27 @@ struct sk_buff *sock_dequeue_err_skb(struct sock *sk)
 }
 EXPORT_SYMBOL(sock_dequeue_err_skb);
 
+struct sk_buff *skb_clone_sk(struct sk_buff *skb)
+{
+	struct sock *sk = skb->sk;
+	struct sk_buff *clone;
+
+	if (!sk || !atomic_inc_not_zero(&sk->sk_refcnt))
+		return NULL;
+
+	clone = skb_clone(skb, GFP_ATOMIC);
+	if (!clone) {
+		sock_put(sk);
+		return NULL;
+	}
+
+	clone->sk = sk;
+	clone->destructor = sock_efree;
+
+	return clone;
+}
+EXPORT_SYMBOL(skb_clone_sk);
+
 static void __skb_complete_tx_timestamp(struct sk_buff *skb,
 					struct sock *sk,
 					int tstype)
@@ -3540,14 +3561,11 @@ void skb_complete_tx_timestamp(struct sk_buff *skb,
 {
 	struct sock *sk = skb->sk;
 
-	skb->sk = NULL;
+	/* take a reference to prevent skb_orphan() from freeing the socket */
+	sock_hold(sk);
 
-	if (hwtstamps) {
-		*skb_hwtstamps(skb) = *hwtstamps;
-		__skb_complete_tx_timestamp(skb, sk, SCM_TSTAMP_SND);
-	} else {
-		kfree_skb(skb);
-	}
+	*skb_hwtstamps(skb) = *hwtstamps;
+	__skb_complete_tx_timestamp(skb, sk, SCM_TSTAMP_SND);
 
 	sock_put(sk);
 }