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Subject[PATCH net v1 1/3] skbuff: skb_clone_sk_optional(): add function to always clone a skb and increase refcount on sk if valid
Date
There already the function skb_clone_sk(), which clones the skb, but
only if the sk is valid.

There are several users in the networking stack, which always need a
clone of a skb with the sk refcount incremented (but only if the sk is
valid). This patch adds such a function.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
include/linux/skbuff.h | 1 +
net/core/skbuff.c | 27 +++++++++++++++++++++++++++
2 files changed, 28 insertions(+)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 6d0a33d1c0db..99d552017508 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3874,6 +3874,7 @@ static inline void skb_metadata_clear(struct sk_buff *skb)
skb_metadata_set(skb, 0);
}

+struct sk_buff *skb_clone_sk_optional(struct sk_buff *skb);
struct sk_buff *skb_clone_sk(struct sk_buff *skb);

#ifdef CONFIG_NETWORK_PHY_TIMESTAMPING
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 545a472273a5..97341f173fb0 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4671,6 +4671,33 @@ struct sk_buff *sock_dequeue_err_skb(struct sock *sk)
}
EXPORT_SYMBOL(sock_dequeue_err_skb);

+/**
+ * skb_clone_sk_optional - create clone of skb, and take reference to socket if
+ * socket is referenced in original skb
+ * @skb: the skb to clone
+ *
+ * This function always creates a clone of a buffer. If it that holds a valid
+ * reference on sk_refcnt this is increased.
+ */
+struct sk_buff *skb_clone_sk_optional(struct sk_buff *skb)
+{
+ struct sock *sk = skb->sk;
+ struct sk_buff *clone;
+
+ clone = skb_clone(skb, GFP_ATOMIC);
+ if (!clone)
+ return NULL;
+
+ if (!sk || !refcount_inc_not_zero(&sk->sk_refcnt))
+ return clone;
+
+ clone->sk = sk;
+ clone->destructor = sock_efree;
+
+ return clone;
+}
+EXPORT_SYMBOL(skb_clone_sk_optional);
+
/**
* skb_clone_sk - create clone of skb, and take reference to socket
* @skb: the skb to clone
--
2.29.2
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