From 690e36e726d00d2528bc569809048adf61550d80 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Sat, 23 Aug 2014 12:13:41 -0700 Subject: net: Allow raw buffers to be passed into the flow dissector. Drivers, and perhaps other entities we have not yet considered, sometimes want to know how deep the protocol headers go before deciding how large of an SKB to allocate and how much of the packet to place into the linear SKB area. For example, consider a driver which has a device which DMAs into pools of pages and then tells the driver where the data went in the DMA descriptor(s). The driver can then build an SKB and reference most of the data via SKB fragments (which are page/offset/length triplets). However at least some of the front of the packet should be placed into the linear SKB area, which comes before the fragments, so that packet processing can get at the headers efficiently. The first thing each protocol layer is going to do is a "pskb_may_pull()" so we might as well aggregate as much of this as possible while we're building the SKB in the driver. Part of supporting this is that we don't have an SKB yet, so we want to be able to let the flow dissector operate on a raw buffer in order to compute the offset of the end of the headers. So now we have a __skb_flow_dissect() which takes an explicit data pointer and length. Signed-off-by: David S. Miller --- include/linux/skbuff.h | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) (limited to 'include/linux/skbuff.h') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index abde271c18ae..18ddf9684a27 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -2567,20 +2567,26 @@ __wsum __skb_checksum(const struct sk_buff *skb, int offset, int len, __wsum skb_checksum(const struct sk_buff *skb, int offset, int len, __wsum csum); -static inline void *skb_header_pointer(const struct sk_buff *skb, int offset, - int len, void *buffer) +static inline void *__skb_header_pointer(const struct sk_buff *skb, int offset, + int len, void *data, int hlen, void *buffer) { - int hlen = skb_headlen(skb); - if (hlen - offset >= len) - return skb->data + offset; + return data + offset; - if (skb_copy_bits(skb, offset, buffer, len) < 0) + if (!skb || + skb_copy_bits(skb, offset, buffer, len) < 0) return NULL; return buffer; } +static inline void *skb_header_pointer(const struct sk_buff *skb, int offset, + int len, void *buffer) +{ + return __skb_header_pointer(skb, offset, len, skb->data, + skb_headlen(skb), buffer); +} + /** * skb_needs_linearize - check if we need to linearize a given skb * depending on the given device features. -- cgit v1.2.3