[MPTCP] [PATCH 1/3] skb: add helpers to allocate ext independently from sk_buff

[MPTCP] [PATCH 1/3] skb: add helpers to allocate ext independently from sk_buff

[Paolo Abeni]

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Currently we can allocate the extension only after the skb,
this change allow the user to do the opposite, will simplify
allocation failure handling from MPTCP.

Signed-off-by: Paolo Abeni <pabeni(a)redhat.com>
---
 include/linux/skbuff.h |  3 +++
 net/core/skbuff.c      | 16 +++++++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index f641fc76f47e..1bbb77640045 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -4111,6 +4111,9 @@ struct skb_ext {
 	char data[0] __aligned(8);
 };
 
+struct skb_ext *skb_ext_alloc(void);
+void *__skb_ext_add(struct sk_buff *skb, enum skb_ext_id id,
+		    struct skb_ext *ext);
 void *skb_ext_add(struct sk_buff *skb, enum skb_ext_id id);
 void __skb_ext_del(struct sk_buff *skb, enum skb_ext_id id);
 void __skb_ext_put(struct skb_ext *ext);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 0aba2cd69881..e8ed6d28fba8 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5981,7 +5981,7 @@ static void *skb_ext_get_ptr(struct skb_ext *ext, enum skb_ext_id id)
 	return (void *)ext + (ext->offset[id] * SKB_EXT_ALIGN_VALUE);
 }
 
-static struct skb_ext *skb_ext_alloc(void)
+struct skb_ext *skb_ext_alloc(void)
 {
 	struct skb_ext *new = kmem_cache_alloc(skbuff_ext_cache, GFP_ATOMIC);
 
@@ -6021,6 +6021,20 @@ static struct skb_ext *skb_ext_maybe_cow(struct skb_ext *old,
 	return new;
 }
 
+void *__skb_ext_add(struct sk_buff *skb, enum skb_ext_id id,
+		    struct skb_ext *ext)
+{
+	unsigned int newlen, newoff = SKB_EXT_CHUNKSIZEOF(*ext);
+
+	skb_ext_put(skb);
+	newlen = newoff + skb_ext_type_len[id];
+	ext->chunks = newlen;
+	ext->offset[id] = newoff;
+	skb->extensions = ext;
+	skb->active_extensions |= 1 << id;
+	return skb_ext_get_ptr(ext, id);
+}
+
 /**
  * skb_ext_add - allocate space for given extension, COW if needed
  * @skb: buffer
-- 
2.21.0