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Message-ID: <158945334261.97035.555255657490688547.stgit@firesoul>
Date: Thu, 14 May 2020 12:49:02 +0200
From: Jesper Dangaard Brouer <brouer@...hat.com>
To: sameehj@...zon.com
Cc: Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org,
bpf@...r.kernel.org,
Toke Høiland-Jørgensen <toke@...hat.com>,
Daniel Borkmann <borkmann@...earbox.net>,
Alexei Starovoitov <alexei.starovoitov@...il.com>,
"David S. Miller" <davem@...emloft.net>,
John Fastabend <john.fastabend@...il.com>,
Alexander Duyck <alexander.duyck@...il.com>,
Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
David Ahern <dsahern@...il.com>,
Ilias Apalodimas <ilias.apalodimas@...aro.org>,
Lorenzo Bianconi <lorenzo@...nel.org>,
Saeed Mahameed <saeedm@...lanox.com>,
Tariq Toukan <tariqt@...lanox.com>
Subject: [PATCH net-next v4 01/33] xdp: add frame size to xdp_buff
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 <brouer@...hat.com>
Acked-by: Toke Høiland-Jørgensen <toke@...hat.com>
---
include/net/xdp.h | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/include/net/xdp.h b/include/net/xdp.h
index 3cc6d5d84aa4..a764af4ae0ea 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 +72,19 @@ 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;
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