From: Jakub Kicinski <kuba@kernel.org>
To: Jakub Sitnicki <jakub@cloudflare.com>
Cc: bpf@vger.kernel.org, "Alexei Starovoitov" <ast@kernel.org>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Arthur Fabre" <arthur@arthurfabre.com>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Eduard Zingerman" <eddyz87@gmail.com>,
"Eric Dumazet" <edumazet@google.com>,
"Jesper Dangaard Brouer" <hawk@kernel.org>,
"Jesse Brandeburg" <jbrandeburg@cloudflare.com>,
"Joanne Koong" <joannelkoong@gmail.com>,
"Lorenzo Bianconi" <lorenzo@kernel.org>,
"Martin KaFai Lau" <martin.lau@linux.dev>,
"Toke Høiland-Jørgensen" <thoiland@redhat.com>,
"Yan Zhai" <yan@cloudflare.com>,
kernel-team@cloudflare.com, netdev@vger.kernel.org,
"Stanislav Fomichev" <sdf@fomichev.me>
Subject: Re: [PATCH bpf-next v4 2/8] bpf: Enable read/write access to skb metadata through a dynptr
Date: Fri, 25 Jul 2025 07:34:14 -0700 [thread overview]
Message-ID: <20250725073414.649ec615@kernel.org> (raw)
In-Reply-To: <87frekwqq0.fsf@cloudflare.com>
On Fri, 25 Jul 2025 11:43:19 +0200 Jakub Sitnicki wrote:
> > Taking about the next step, once skb metadata is preserved past the TC
> > hook - here my impression from Netdev was that the least suprising thing
> > to do will be to copy-on-clone or copy-on-write (if we can pull it off).
>
> Now that Martin has enlightened me [1] how things work today for skb
> payload dynptr's, I will first try to follow the same approach, that is:
>
> Make a copy of skb metadata before the BPF program runs, if the program
> may write to the metadata.
👍️
On the pskb_expand_head() behavior we should probably ask Daniel?
I suspect it's just to "fail closed". But as you said we can follow
up on that later, not a blocker in practice on Rx.
next prev parent reply other threads:[~2025-07-25 14:34 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-23 17:36 [PATCH bpf-next v4 0/8] Add a dynptr type for skb metadata for TC BPF Jakub Sitnicki
2025-07-23 17:36 ` [PATCH bpf-next v4 1/8] bpf: Add dynptr type for skb metadata Jakub Sitnicki
2025-07-24 1:54 ` Martin KaFai Lau
2025-07-24 11:56 ` Jakub Sitnicki
2025-07-23 17:36 ` [PATCH bpf-next v4 2/8] bpf: Enable read/write access to skb metadata through a dynptr Jakub Sitnicki
2025-07-23 21:58 ` Eduard Zingerman
2025-07-24 0:02 ` Martin KaFai Lau
2025-07-24 9:44 ` Jakub Sitnicki
2025-07-24 0:30 ` Jakub Kicinski
2025-07-24 11:53 ` Jakub Sitnicki
2025-07-24 15:52 ` Martin KaFai Lau
2025-07-24 19:43 ` Jakub Sitnicki
2025-07-25 9:43 ` Jakub Sitnicki
2025-07-25 14:34 ` Jakub Kicinski [this message]
2025-07-23 17:36 ` [PATCH bpf-next v4 3/8] selftests/bpf: Cover verifier checks for skb_meta dynptr type Jakub Sitnicki
2025-07-23 17:36 ` [PATCH bpf-next v4 4/8] selftests/bpf: Pass just bpf_map to xdp_context_test helper Jakub Sitnicki
2025-07-23 17:36 ` [PATCH bpf-next v4 5/8] selftests/bpf: Parametrize test_xdp_context_tuntap Jakub Sitnicki
2025-07-23 17:36 ` [PATCH bpf-next v4 6/8] selftests/bpf: Cover read access to skb metadata via dynptr Jakub Sitnicki
2025-07-23 17:36 ` [PATCH bpf-next v4 7/8] selftests/bpf: Cover write " Jakub Sitnicki
2025-07-23 17:36 ` [PATCH bpf-next v4 8/8] selftests/bpf: Cover read/write to skb metadata at an offset Jakub Sitnicki
2025-07-23 22:02 ` Eduard Zingerman
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