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From: Oleksij Rempel <o.rempel@pengutronix.de>
To: mkl@pengutronix.de, "David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Oliver Hartkopp <socketcan@hartkopp.net>,
	Robin van der Gracht <robin@protonic.nl>,
	Johannes Berg <johannes@sipsolutions.net>
Cc: Oleksij Rempel <o.rempel@pengutronix.de>,
	kernel@pengutronix.de, linux-can@vger.kernel.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	Eric Dumazet <edumazet@google.com>,
	linux-wireless@vger.kernel.org
Subject: [PATCH net v2 1/2] skbuff: skb_clone_sk_optional(): add function to always clone a skb and increase refcount on sk if valid
Date: Tue, 23 Feb 2021 06:53:19 +0100
Message-ID: <20210223055321.3891-2-o.rempel@pengutronix.de> (raw)
In-Reply-To: <20210223055321.3891-1-o.rempel@pengutronix.de>

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


  reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-23  5:53 [PATCH net v2 0/2] add support for skb with sk ref cloning Oleksij Rempel
2021-02-23  5:53 ` Oleksij Rempel [this message]
2021-02-23  5:53 ` [PATCH net v2 2/2] can: fix ref count warning if socket was closed before skb was cloned Oleksij Rempel
2021-02-23  8:55   ` Eric Dumazet

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