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From: Jakub Sitnicki <jakub@cloudflare.com>
To: Jakub Kicinski <kuba@kernel.org>
Cc: bpf@vger.kernel.org,  netdev@vger.kernel.org,
	 "David S. Miller" <davem@davemloft.net>,
	 Eric Dumazet <edumazet@google.com>,
	 Paolo Abeni <pabeni@redhat.com>,
	 Alexei Starovoitov <ast@kernel.org>,
	 Daniel Borkmann <daniel@iogearbox.net>,
	 Jesper Dangaard Brouer <hawk@kernel.org>,
	 John Fastabend <john.fastabend@gmail.com>,
	 Stanislav Fomichev <sdf@fomichev.me>,
	 Simon Horman <horms@kernel.org>,
	 Andrii Nakryiko <andrii@kernel.org>,
	 Martin KaFai Lau <martin.lau@linux.dev>,
	Eduard Zingerman <eddyz87@gmail.com>,  Song Liu <song@kernel.org>,
	Yonghong Song <yonghong.song@linux.dev>,
	 KP Singh <kpsingh@kernel.org>, Hao Luo <haoluo@google.com>,
	 Jiri Olsa <jolsa@kernel.org>,
	kernel-team@cloudflare.com
Subject: Re: [PATCH bpf-next v3 00/17] Decouple skb metadata tracking from MAC header offset
Date: Fri, 09 Jan 2026 11:50:03 +0100	[thread overview]
Message-ID: <875x9bhxgk.fsf@cloudflare.com> (raw)
In-Reply-To: <20260108174903.59323f72@kernel.org> (Jakub Kicinski's message of "Thu, 8 Jan 2026 17:49:03 -0800")

On Thu, Jan 08, 2026 at 05:49 PM -08, Jakub Kicinski wrote:
> To reduce the one-off feeling of the mechanism it'd be great to shove
> this state into an skb extension for example. Then if we optimize it
> and possibly make it live inline in the frame all the other skb
> extensions will benefit too.

Back to the drawing board then.

Here's how I think we can marry it with skb extension:

1. Move metadata from headroom to skb_ext chunk on skb_metadata_set().

2. If TC BPF prog uses data_meta pseudo-pointer, copy metadata contents
   in and out of headroom in BPF prologue and epilogue.

3. If TC BPF prog uses bpf_dynptr_from_skb_meta(), access the skb_ext
   chunk directly.

If that sounds sane, then I'll get cracking on an RFC.

We will need the driver tweaks from this series for (1) to work, so I'm
thinking to split that out and resubmit.

I would also split out the BPF verifier prologue/epilogue processing
tweaks for (2) to work without kfuncs.

Let me know what you think.

Thanks,
-jkbs

      reply	other threads:[~2026-01-09 10:50 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-01-07 14:28 [PATCH bpf-next v3 00/17] Decouple skb metadata tracking from MAC header offset Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 01/17] bnxt_en: Call skb_metadata_set when skb->data points at metadata end Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 02/17] i40e: " Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 03/17] igb: " Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 04/17] igc: " Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 05/17] ixgbe: " Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 06/17] net/mlx5e: " Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 07/17] veth: " Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 08/17] xsk: " Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 09/17] xdp: " Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 10/17] net: Track skb metadata end separately from MAC offset Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 11/17] bpf, verifier: Remove side effects from may_access_direct_pkt_data Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 12/17] bpf, verifier: Turn seen_direct_write flag into a bitmap Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 13/17] bpf, verifier: Propagate packet access flags to gen_prologue Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 14/17] bpf, verifier: Track when data_meta pointer is loaded Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 15/17] bpf, verifier: Support direct kernel calls in gen_prologue Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 16/17] bpf: Realign skb metadata for TC progs using data_meta Jakub Sitnicki
2026-01-07 22:01   ` Alexei Starovoitov
2026-01-08 19:54     ` Jakub Sitnicki
2026-01-07 14:28 ` [PATCH bpf-next v3 17/17] selftests/bpf: Test skb metadata access after L2 decapsulation Jakub Sitnicki
2026-01-08 15:47 ` [PATCH bpf-next v3 00/17] Decouple skb metadata tracking from MAC header offset Jakub Kicinski
2026-01-08 19:25   ` Jakub Sitnicki
2026-01-09  1:49     ` Jakub Kicinski
2026-01-09 10:50       ` Jakub Sitnicki [this message]

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