networking: add and use skb_put_u8()

Joe and Bjørn suggested that it'd be nicer to not have the
cast in the fairly common case of doing
	*(u8 *)skb_put(skb, 1) = c;

Add skb_put_u8() for this case, and use it across the code,
using the following spatch:

    @@
    expression SKB, C, S;
    typedef u8;
    identifier fn = {skb_put};
    fresh identifier fn2 = fn ## "_u8";
    @@
    - *(u8 *)fn(SKB, S) = C;
    + fn2(SKB, C);

Note that due to the "S", the spatch isn't perfect, it should
have checked that S is 1, but there's also places that use a
sizeof expression like sizeof(var) or sizeof(u8) etc. Turns
out that nobody ever did something like
	*(u8 *)skb_put(skb, 2) = c;

which would be wrong anyway since the second byte wouldn't be
initialized.

Suggested-by: Joe Perches <joe@perches.com>
Suggested-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 0 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 46bd514e719c..852feacf4bbf 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1923,6 +1923,11 @@ static inline void *skb_put_data(struct sk_buff *skb, const void *data,
 	return tmp;
 }
 
+static inline void skb_put_u8(struct sk_buff *skb, u8 val)
+{
+	*(u8 *)skb_put(skb, 1) = val;
+}
+
 void *skb_push(struct sk_buff *skb, unsigned int len);
 static inline void *__skb_push(struct sk_buff *skb, unsigned int len)
 {