On Fri, 2017-06-16 at 14:29 +0200, Johannes Berg wrote: > Changes from v1: > * add skb_put_u8() as suggested by Joe and Bjørn > > Again build-tested by myself and kbuild bot.
Now that I think about it, I did something similar in 2015 https://www.spinics.net/lists/netdev/msg327404.html At that time Eric Dumazet objected to the API expansion. And here's an FYI that was a bit surprising to me: Adding separate EXPORT_SYMBOL functions for skb_put_zero and skb_put_data that do the memset/memcpy does not shrink an x86-64 defconfig kernel image much at all. $ size vmlinux.new vmlinux.old text data bss dec hex filename 10779941 4707128 892928 16379997 f9f05d vmlinux.new 10780631 4707128 892928 16380687 f9f30f vmlinux.old This was the patch I tested: --- diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 852feacf4bbf..9de7c642ee4f 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -1904,24 +1904,8 @@ static inline void *__skb_put(struct sk_buff *skb, unsigned int len) return tmp; } -static inline void *skb_put_zero(struct sk_buff *skb, unsigned int len) -{ - void *tmp = skb_put(skb, len); - - memset(tmp, 0, len); - - return tmp; -} - -static inline void *skb_put_data(struct sk_buff *skb, const void *data, - unsigned int len) -{ - void *tmp = skb_put(skb, len); - - memcpy(tmp, data, len); - - return tmp; -} +void *skb_put_zero(struct sk_buff *skb, unsigned int len); +void *skb_put_data(struct sk_buff *skb, const void *data, unsigned int len); static inline void skb_put_u8(struct sk_buff *skb, u8 val) { diff --git a/net/core/skbuff.c b/net/core/skbuff.c index f75897a33fa4..327f7cd2e0bb 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1431,6 +1431,19 @@ void *pskb_put(struct sk_buff *skb, struct sk_buff *tail, int len) } EXPORT_SYMBOL_GPL(pskb_put); +static __always_inline void *___skb_put(struct sk_buff *skb, unsigned int len) +{ + void *tmp = skb_tail_pointer(skb); + + SKB_LINEAR_ASSERT(skb); + skb->tail += len; + skb->len += len; + if (unlikely(skb->tail > skb->end)) + skb_over_panic(skb, len, __builtin_return_address(0)); + + return tmp; +} + /** * skb_put - add data to a buffer * @skb: buffer to use @@ -1442,17 +1455,42 @@ EXPORT_SYMBOL_GPL(pskb_put); */ void *skb_put(struct sk_buff *skb, unsigned int len) { - void *tmp = skb_tail_pointer(skb); - SKB_LINEAR_ASSERT(skb); - skb->tail += len; - skb->len += len; - if (unlikely(skb->tail > skb->end)) - skb_over_panic(skb, len, __builtin_return_address(0)); - return tmp; + return ___skb_put(skb, len); } EXPORT_SYMBOL(skb_put); /** + * skb_put_zero - add zeroed data to a buffer + * @skb: buffer to use + * @len: amount of zeroed data to add + * + * This function extends the used data area of the buffer. If this would + * exceed the total buffer size the kernel will panic. A pointer to the + * first byte of the extra data is returned. + */ +void *skb_put_zero(struct sk_buff *skb, unsigned int len) +{ + return memset(___skb_put(skb, len), 0, len); +} +EXPORT_SYMBOL(skb_put_zero); + +/** + * skb_put_data - Copy data to a buffer + * @skb: buffer to use + * @data: pointer to data to copy + * @len: amount of data to add + * + * This function extends the used data area of the buffer. If this would + * exceed the total buffer size the kernel will panic. A pointer to the + * first byte of the extra data is returned. + */ +void *skb_put_data(struct sk_buff *skb, const void *data, unsigned int len) +{ + return memcpy(___skb_put(skb, len), data, len); +} +EXPORT_SYMBOL(skb_put_data); + +/** * skb_push - add data to the start of a buffer * @skb: buffer to use * @len: amount of data to add
