From f95f0f95cfb7f180ed7571d4915432d5098df7ec Mon Sep 17 00:00:00 2001 From: Jesper Dangaard Brouer Date: Thu, 14 May 2020 12:49:02 +0200 Subject: [PATCH] xdp: Add frame size to xdp_buff MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit XDP have evolved to support several frame sizes, but xdp_buff was not updated with this information. The frame size (frame_sz) member of xdp_buff is introduced to know the real size of the memory the frame is delivered in. When introducing this also make it clear that some tailroom is reserved/required when creating SKBs using build_skb(). It would also have been an option to introduce a pointer to data_hard_end (with reserved offset). The advantage with frame_sz is that (like rxq) drivers only need to setup/assign this value once per NAPI cycle. Due to XDP-generic (and some drivers) it's not possible to store frame_sz inside xdp_rxq_info, because it's varies per packet as it can be based/depend on packet length. V2: nitpick: deduct -> deduce Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Alexei Starovoitov Acked-by: Toke Høiland-Jørgensen Link: https://lore.kernel.org/bpf/158945334261.97035.555255657490688547.stgit@firesoul --- include/net/xdp.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/include/net/xdp.h b/include/net/xdp.h index 3cc6d5d..a764af4 100644 --- a/include/net/xdp.h +++ b/include/net/xdp.h @@ -6,6 +6,8 @@ #ifndef __LINUX_NET_XDP_H__ #define __LINUX_NET_XDP_H__ +#include /* skb_shared_info */ + /** * DOC: XDP RX-queue information * @@ -70,8 +72,19 @@ struct xdp_buff { void *data_hard_start; unsigned long handle; struct xdp_rxq_info *rxq; + u32 frame_sz; /* frame size to deduce data_hard_end/reserved tailroom*/ }; +/* Reserve memory area at end-of data area. + * + * This macro reserves tailroom in the XDP buffer by limiting the + * XDP/BPF data access to data_hard_end. Notice same area (and size) + * is used for XDP_PASS, when constructing the SKB via build_skb(). + */ +#define xdp_data_hard_end(xdp) \ + ((xdp)->data_hard_start + (xdp)->frame_sz - \ + SKB_DATA_ALIGN(sizeof(struct skb_shared_info))) + struct xdp_frame { void *data; u16 len; -- 2.7.4