net: move pskb_put() to core code

This function has usage beside IPsec so move it to the core skbuff code.
While doing so, give it some documentation and change its return type to
'unsigned char *' to be in line with skb_put().

Signed-off-by: Mathias Krause <[e-mail]>
Cc: Steffen Klassert <[e-mail]>
Cc: "David S. Miller" <[e-mail]>
Cc: Herbert Xu <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/linux/skbuff.h

···
 /*
  *	Add data to an sk_buff
  */
+unsigned char *pskb_put(struct sk_buff *skb, struct sk_buff *tail, int len);
 unsigned char *skb_put(struct sk_buff *skb, unsigned int len);
 static inline unsigned char *__skb_put(struct sk_buff *skb, unsigned int len)
 {

include/net/esp.h

···
 
 #include <linux/skbuff.h>
 
-void *pskb_put(struct sk_buff *skb, struct sk_buff *tail, int len);
-
 struct ip_esp_hdr;
 
 static inline struct ip_esp_hdr *ip_esp_hdr(const struct sk_buff *skb)

net/core/skbuff.c

···
 EXPORT_SYMBOL(skb_pad);
 
 /**
+ *	pskb_put - add data to the tail of a potentially fragmented buffer
+ *	@skb: start of the buffer to use
+ *	@tail: tail fragment of the buffer to use
+ *	@len: amount of data to add
+ *
+ *	This function extends the used data area of the potentially
+ *	fragmented buffer. @tail must be the last fragment of @skb -- or
+ *	@skb itself. If this would exceed the total buffer size the kernel
+ *	will panic. A pointer to the first byte of the extra data is
+ *	returned.
+ */
+
+unsigned char *pskb_put(struct sk_buff *skb, struct sk_buff *tail, int len)
+{
+	if (tail != skb) {
+		skb->data_len += len;
+		skb->len += len;
+	}
+	return skb_put(tail, len);
+}
+EXPORT_SYMBOL_GPL(pskb_put);
+
+/**
  *	skb_put - add data to a buffer
  *	@skb: buffer to use
  *	@len: amount of data to add

net/xfrm/xfrm_algo.c

···
 }
 EXPORT_SYMBOL_GPL(xfrm_count_pfkey_enc_supported);
 
-#if defined(CONFIG_INET_ESP) || defined(CONFIG_INET_ESP_MODULE) || defined(CONFIG_INET6_ESP) || defined(CONFIG_INET6_ESP_MODULE)
-
-void *pskb_put(struct sk_buff *skb, struct sk_buff *tail, int len)
-{
-	if (tail != skb) {
-		skb->data_len += len;
-		skb->len += len;
-	}
-	return skb_put(tail, len);
-}
-EXPORT_SYMBOL_GPL(pskb_put);
-#endif
-
 MODULE_LICENSE("GPL");