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>

6 files changed, 40 insertions, 21 deletions

diff --git a/drivers/net/phy/dp83640.c b/drivers/net/phy/dp83640.c
index d5991ac46ab0..87648b306551 100644
--- a/drivers/net/phy/dp83640.c
+++ b/drivers/net/phy/dp83640.c
@@ -1148,7 +1148,7 @@ static void dp83640_remove(struct phy_device *phydev)
                 kfree_skb(skb);
 
         while ((skb = skb_dequeue(&dp83640->tx_queue)) != NULL)
-                skb_complete_tx_timestamp(skb, NULL);
+                kfree_skb(skb);
 
         clock = dp83640_clock_get(dp83640->clock);
 
@@ -1405,7 +1405,7 @@ static void dp83640_txtstamp(struct phy_device *phydev,
 
         case HWTSTAMP_TX_ONESTEP_SYNC:
                 if (is_sync(skb, type)) {
-                        skb_complete_tx_timestamp(skb, NULL);
+                        kfree_skb(skb);
                         return;
                 }
                 /* fall through */
@@ -1416,7 +1416,7 @@ static void dp83640_txtstamp(struct phy_device *phydev,
 
         case HWTSTAMP_TX_OFF:
         default:
-                skb_complete_tx_timestamp(skb, NULL);
+                kfree_skb(skb);
                 break;
         }
 }
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 02529fcad1ac..1cf0cfaef10a 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2690,6 +2690,8 @@ static inline ktime_t net_invalid_timestamp(void)
         return ktime_set(0, 0);
 }
 
+struct sk_buff *skb_clone_sk(struct sk_buff *skb);
+
 #ifdef CONFIG_NETWORK_PHY_TIMESTAMPING
 
 void skb_clone_tx_timestamp(struct sk_buff *skb);
diff --git a/include/net/sock.h b/include/net/sock.h
index 3fde6130789d..e02be37a3d91 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1574,6 +1574,7 @@ struct sk_buff *sock_wmalloc(struct sock *sk, unsigned long size, int force,
 void sock_wfree(struct sk_buff *skb);
 void skb_orphan_partial(struct sk_buff *skb);
 void sock_rfree(struct sk_buff *skb);
+void sock_efree(struct sk_buff *skb);
 void sock_edemux(struct sk_buff *skb);
 
 int sock_setsockopt(struct socket *sock, int level, int op,
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 697e696c914b..a936a401564e 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);
 }
diff --git a/net/core/sock.c b/net/core/sock.c
index f1a638ee93d9..d04005c51724 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1637,6 +1637,12 @@ void sock_rfree(struct sk_buff *skb)
 }
 EXPORT_SYMBOL(sock_rfree);
 
+void sock_efree(struct sk_buff *skb)
+{
+        sock_put(skb->sk);
+}
+EXPORT_SYMBOL(sock_efree);
+
 void sock_edemux(struct sk_buff *skb)
 {
         struct sock *sk = skb->sk;
diff --git a/net/core/timestamping.c b/net/core/timestamping.c
index f48a59fd8f39..43d3dd62fcc8 100644
--- a/net/core/timestamping.c
+++ b/net/core/timestamping.c
@@ -36,10 +36,9 @@ void skb_clone_tx_timestamp(struct sk_buff *skb)
 {
         struct phy_device *phydev;
         struct sk_buff *clone;
-        struct sock *sk = skb->sk;
         unsigned int type;
 
-        if (!sk)
+        if (!skb->sk)
                 return;
 
         type = classify(skb);
@@ -48,16 +47,9 @@ void skb_clone_tx_timestamp(struct sk_buff *skb)
 
         phydev = skb->dev->phydev;
         if (likely(phydev->drv->txtstamp)) {
-                if (!atomic_inc_not_zero(&sk->sk_refcnt))
+                clone = skb_clone_sk(skb);
+                if (!clone)
                         return;
-
-                clone = skb_clone(skb, GFP_ATOMIC);
-                if (!clone) {
-                        sock_put(sk);
-                        return;
-                }
-
-                clone->sk = sk;
                 phydev->drv->txtstamp(phydev, clone, type);
         }
 }