net: Rename and export copy_skb_header

copy_skb_header is renamed to skb_copy_header and
exported. Exposing this function give more flexibility
in copying SKBs.
skb_copy and skb_copy_expand do not give enough control
over which parts are copied.

Signed-off-by: Ilya Lesokhin <[email protected]>
Signed-off-by: Boris Pismenny <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: Ilya Lesokhin

include/linux/skbuff.h

@@ -1034,6 +1034,7 @@ static inline struct sk_buff *alloc_skb_fclone(unsigned int size,
 struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src);
 int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask);
 struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t priority);
+void skb_copy_header(struct sk_buff *new, const struct sk_buff *old);
 struct sk_buff *skb_copy(const struct sk_buff *skb, gfp_t priority);
 struct sk_buff *__pskb_copy_fclone(struct sk_buff *skb, int headroom,
 				   gfp_t gfp_mask, bool fclone);

net/core/skbuff.c

@@ -1305,14 +1305,15 @@ static void skb_headers_offset_update(struct sk_buff *skb, int off)
 	skb->inner_mac_header += off;
 }
 
-static void copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
+void skb_copy_header(struct sk_buff *new, const struct sk_buff *old)
 {
 	__copy_skb_header(new, old);
 
 	skb_shinfo(new)->gso_size = skb_shinfo(old)->gso_size;
 	skb_shinfo(new)->gso_segs = skb_shinfo(old)->gso_segs;
 	skb_shinfo(new)->gso_type = skb_shinfo(old)->gso_type;
 }
+EXPORT_SYMBOL(skb_copy_header);
 
 static inline int skb_alloc_rx_flag(const struct sk_buff *skb)
 {
@@ -1355,7 +1356,7 @@ struct sk_buff *skb_copy(const struct sk_buff *skb, gfp_t gfp_mask)
 
 	BUG_ON(skb_copy_bits(skb, -headerlen, n->head, headerlen + skb->len));
 
-	copy_skb_header(n, skb);
+	skb_copy_header(n, skb);
 	return n;
 }
 EXPORT_SYMBOL(skb_copy);
@@ -1419,7 +1420,7 @@ struct sk_buff *__pskb_copy_fclone(struct sk_buff *skb, int headroom,
 		skb_clone_fraglist(n);
 	}
 
-	copy_skb_header(n, skb);
+	skb_copy_header(n, skb);
 out:
 	return n;
 }
@@ -1599,7 +1600,7 @@ struct sk_buff *skb_copy_expand(const struct sk_buff *skb,
 	BUG_ON(skb_copy_bits(skb, -head_copy_len, n->head + head_copy_off,
 			     skb->len + head_copy_len));
 
-	copy_skb_header(n, skb);
+	skb_copy_header(n, skb);
 
 	skb_headers_offset_update(n, newheadroom - oldheadroom);