networking: make skb_push & __skb_push return void pointers

It seems like a historic accident that these return unsigned char *,
and in many places that means casts are required, more often than not.

Make these functions return void * and remove all the casts across
the tree, adding a (u8 *) cast only where the unsigned char pointer
was used directly, all done with the following spatch:

    @@
    expression SKB, LEN;
    typedef u8;
    identifier fn = { skb_push, __skb_push, skb_push_rcsum };
    @@
    - *(fn(SKB, LEN))
    + *(u8 *)fn(SKB, LEN)

    @@
    expression E, SKB, LEN;
    identifier fn = { skb_push, __skb_push, skb_push_rcsum };
    type T;
    @@
    - E = ((T *)(fn(SKB, LEN)))
    + E = fn(SKB, LEN)

    @@
    expression SKB, LEN;
    identifier fn = { skb_push, __skb_push, skb_push_rcsum };
    @@
    - fn(SKB, LEN)[0]
    + *(u8 *)fn(SKB, LEN)

Note that the last part there converts from push(...)[0] to the
more idiomatic *(u8 *)push(...).

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 4 insertions, 5 deletions

diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h
index 283dc2f5364d..5e6a2d4dc366 100644
--- a/include/linux/if_vlan.h
+++ b/include/linux/if_vlan.h
@@ -318,7 +318,7 @@ static inline int __vlan_insert_tag(struct sk_buff *skb,
 	if (skb_cow_head(skb, VLAN_HLEN) < 0)
 		return -ENOMEM;
 
-	veth = (struct vlan_ethhdr *)skb_push(skb, VLAN_HLEN);
+	veth = skb_push(skb, VLAN_HLEN);
 
 	/* Move the mac addresses to the beginning of the new header. */
 	memmove(skb->data, skb->data + VLAN_HLEN, 2 * ETH_ALEN);
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index ac9d10dadd1a..46bd514e719c 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1923,8 +1923,8 @@ static inline void *skb_put_data(struct sk_buff *skb, const void *data,
 	return tmp;
 }
 
-unsigned char *skb_push(struct sk_buff *skb, unsigned int len);
-static inline unsigned char *__skb_push(struct sk_buff *skb, unsigned int len)
+void *skb_push(struct sk_buff *skb, unsigned int len);
+static inline void *__skb_push(struct sk_buff *skb, unsigned int len)
 {
 	skb->data -= len;
 	skb->len  += len;
@@ -2951,8 +2951,7 @@ void *skb_pull_rcsum(struct sk_buff *skb, unsigned int len);
  *	that the checksum difference is zero (e.g., a valid IP header)
  *	or you are setting ip_summed to CHECKSUM_NONE.
  */
-static inline unsigned char *skb_push_rcsum(struct sk_buff *skb,
-					    unsigned int len)
+static inline void *skb_push_rcsum(struct sk_buff *skb, unsigned int len)
 {
 	skb_push(skb, len);
 	skb_postpush_rcsum(skb, skb->data, len);