From: Vasily Averin <vvs@xxxxxxxxxxxxx>
[ Upstream commit f1260ff15a71b8fc122b2c9abd8a7abffb6e0168 ]
Like skb_realloc_headroom(), new helper increases headroom of specified skb.
Unlike skb_realloc_headroom(), it does not allocate a new skb if possible;
copies skb->sk on new skb when as needed and frees original skb in case
of failures.
This helps to simplify ip[6]_finish_output2() and a few other similar cases.
Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
(cherry picked from commit f1260ff15a71b8fc122b2c9abd8a7abffb6e0168)
Signed-off-by: Harshvardhan Jha <harshvardhan.j.jha@xxxxxxxxxx>
---
include/linux/skbuff.h | 1 +
net/core/skbuff.c | 42 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 43 insertions(+)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 31ae4b74d4352..3248e4aeec037 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1166,6 +1166,7 @@ static inline struct sk_buff *__pskb_copy(struct sk_buff *skb, int headroom,
int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, gfp_t gfp_mask);
struct sk_buff *skb_realloc_headroom(struct sk_buff *skb,
unsigned int headroom);
+struct sk_buff *skb_expand_head(struct sk_buff *skb, unsigned int headroom);
struct sk_buff *skb_copy_expand(const struct sk_buff *skb, int newheadroom,
int newtailroom, gfp_t priority);
int __must_check skb_to_sgvec_nomark(struct sk_buff *skb, struct scatterlist *sg,
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index b0c2d6f018003..fa3ea287d6ecc 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1732,6 +1732,48 @@ struct sk_buff *skb_realloc_headroom(struct sk_buff *skb, unsigned int headroom)
}
EXPORT_SYMBOL(skb_realloc_headroom);
+/**
+ * skb_expand_head - reallocate header of &sk_buff
+ * @skb: buffer to reallocate
+ * @headroom: needed headroom
+ *
+ * Unlike skb_realloc_headroom, this one does not allocate a new skb
+ * if possible; copies skb->sk to new skb as needed
+ * and frees original skb in case of failures.
+ *
+ * It expect increased headroom and generates warning otherwise.
+ */
+
+struct sk_buff *skb_expand_head(struct sk_buff *skb, unsigned int headroom)
+{
+ int delta = headroom - skb_headroom(skb);
+
+ if (WARN_ONCE(delta <= 0,
+ "%s is expecting an increase in the headroom", __func__))
+ return skb;
+
+ /* pskb_expand_head() might crash, if skb is shared */
+ if (skb_shared(skb)) {
+ struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
+
+ if (likely(nskb)) {
+ if (skb->sk)
+ skb_set_owner_w(nskb, skb->sk);
+ consume_skb(skb);
+ } else {
+ kfree_skb(skb);
+ }
+ skb = nskb;
+ }
+ if (skb &&
+ pskb_expand_head(skb, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC)) {
+ kfree_skb(skb);
+ skb = NULL;
+ }
+ return skb;
+}
+EXPORT_SYMBOL(skb_expand_head);
+
/**
* skb_copy_expand - copy and expand sk_buff
* @skb: buffer to copy
--
2.46.0
