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Message-Id: <20231229081409.1276386-1-menglong8.dong@gmail.com>
Date: Fri, 29 Dec 2023 16:14:07 +0800
From: Menglong Dong <menglong8.dong@...il.com>
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Subject: [PATCH bpf-next 0/2] bpf: add csum/ip_summed fields to __sk_buff
For now, we have to call some helpers when we need to update the csum,
such as bpf_l4_csum_replace, bpf_l3_csum_replace, etc. These helpers are
not inlined, which causes poor performance.
In fact, we can define our own csum update functions in BPF program
instead of bpf_l3_csum_replace, which is totally inlined and efficient.
However, we can't do this for bpf_l4_csum_replace for now, as we can't
update skb->csum, which can cause skb->csum invalid in the rx path with
CHECKSUM_COMPLETE mode.
What's more, we can't use the direct data access and have to use
skb_store_bytes() with the BPF_F_RECOMPUTE_CSUM flag in some case, such
as modifing the vni in the vxlan header and the underlay udp header has
no checksum.
In the first patch, we make skb->csum readable and writable, and we make
skb->ip_summed readable. For now, for tc only. With these 2 fields, we
don't need to call bpf helpers for csum update any more.
In the second patch, we add some testcases for the read/write testing for
skb->csum and skb->ip_summed.
If this series is acceptable, we can define the inlined functions for csum
update in libbpf in the next step.
Menglong Dong (2):
bpf: add csum/ip_summed fields to __sk_buff
testcases/bpf: add testcases for skb->csum to ctx_skb.c
include/linux/skbuff.h | 2 +
include/uapi/linux/bpf.h | 2 +
net/core/filter.c | 22 ++++++++++
tools/include/uapi/linux/bpf.h | 2 +
.../testing/selftests/bpf/verifier/ctx_skb.c | 43 +++++++++++++++++++
5 files changed, 71 insertions(+)
--
2.39.2
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