[PATCH RFC v2 01/33] xdp: add frame size to xdp_buff
flat view
STALE2385d
SUPERSEDED
From: Jesper Dangaard Brouer <hidden>
Date: 2020-04-08 11:50:52
Also in:
bpf
Subsystem:
networking [general], the rest, xdp (express data path) · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, Alexei Starovoitov, Daniel Borkmann, Jesper Dangaard Brouer, John Fastabend
Status: Superseded by v4 (posted 2020-05-14). [go to v4]
Revision v2 (4 revisions archived).
Revisions (4)
- v1 re-posted go to this post
- v2 current [diff against previous] re-posted go to this post
- v3 [diff against previous]
- v4 [diff against previous]
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. Signed-off-by: Jesper Dangaard Brouer <redacted> --- include/net/xdp.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)
diff --git a/include/net/xdp.h b/include/net/xdp.h
index 40c6d3398458..99f4374f6214 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 <linux/skbuff.h> /* skb_shared_info */ + /** * DOC: XDP RX-queue information *
@@ -70,8 +72,23 @@ struct xdp_buff { void *data_hard_start; unsigned long handle; struct xdp_rxq_info *rxq; + u32 frame_sz; /* frame size to deduct 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))) + +/* Like skb_shinfo */ +#define xdp_shinfo(xdp) ((struct skb_shared_info *)(xdp_data_hard_end(xdp))) +// XXX: Above likely belongs in later patch + struct xdp_frame { void *data; u16 len;