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From: Jesper Dangaard Brouer <jbrouer@redhat.com>
To: Stanislav Fomichev <sdf@google.com>, bpf@vger.kernel.org
Cc: brouer@redhat.com, ast@kernel.org, daniel@iogearbox.net,
	andrii@kernel.org, martin.lau@linux.dev, song@kernel.org,
	yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org,
	haoluo@google.com, jolsa@kernel.org,
	David Ahern <dsahern@gmail.com>, Jakub Kicinski <kuba@kernel.org>,
	Willem de Bruijn <willemb@google.com>,
	Anatoly Burakov <anatoly.burakov@intel.com>,
	Alexander Lobakin <alexandr.lobakin@intel.com>,
	Magnus Karlsson <magnus.karlsson@gmail.com>,
	Maryam Tahhan <mtahhan@redhat.com>,
	xdp-hints@xdp-project.net, netdev@vger.kernel.org
Subject: [xdp-hints] Re: [PATCH bpf-next 06/11] xdp: Carry over xdp metadata into skb context
Date: Fri, 18 Nov 2022 15:05:30 +0100	[thread overview]
Message-ID: <e26f75dd-f52f-a69b-6754-54e1fe044a42@redhat.com> (raw)
In-Reply-To: <20221115030210.3159213-7-sdf@google.com>


On 15/11/2022 04.02, Stanislav Fomichev wrote:
> Implement new bpf_xdp_metadata_export_to_skb kfunc which
> prepares compatible xdp metadata for kernel consumption.
> This kfunc should be called prior to bpf_redirect
> or when XDP_PASS'ing the frame into the kernel (note, the drivers
> have to be updated to enable consuming XDP_PASS'ed metadata).
> 
> veth driver is amended to consume this metadata when converting to skb.
> 
> Internally, XDP_FLAGS_HAS_SKB_METADATA flag is used to indicate
> whether the frame has skb metadata. The metadata is currently
> stored prior to xdp->data_meta. bpf_xdp_adjust_meta refuses
> to work after a call to bpf_xdp_metadata_export_to_skb (can lift
> this requirement later on if needed, we'd have to memmove
> xdp_skb_metadata).
> 

I think it is wrong to refuses using metadata area (bpf_xdp_adjust_meta)
when the function bpf_xdp_metadata_export_to_skb() have been called.
In my design they were suppose to co-exist, and BPF-prog was expected to
access this directly themselves.

With this current design, I think it is better to place the struct
xdp_skb_metadata (maybe call it xdp_skb_hints) after xdp_frame (in the
top of the frame).  This way we don't conflict with metadata and
headroom use-cases.  Plus, verifier will keep BPF-prog from accessing
this area directly (which seems to be one of the new design goals).

By placing it after xdp_frame, I think it would be possible to let veth 
unroll functions seamlessly access this info for XDP_REDIRECT'ed 
xdp_frame's.

WDYT?

--Jesper


  parent reply	other threads:[~2022-11-18 14:05 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-15  3:01 [xdp-hints] [PATCH bpf-next 00/11] xdp: hints via kfuncs Stanislav Fomichev
2022-11-15  3:02 ` [xdp-hints] [PATCH bpf-next 02/11] bpf: Introduce bpf_patch Stanislav Fomichev
2022-11-15  3:02 ` [xdp-hints] [PATCH bpf-next 03/11] bpf: Support inlined/unrolled kfuncs for xdp metadata Stanislav Fomichev
2022-11-15 16:16   ` [xdp-hints] " Toke Høiland-Jørgensen
2022-11-15 18:37     ` Stanislav Fomichev
2022-11-16 20:42   ` Jakub Kicinski
2022-11-16 20:53     ` Stanislav Fomichev
2022-11-15  3:02 ` [xdp-hints] [PATCH bpf-next 05/11] veth: Support rx timestamp metadata for xdp Stanislav Fomichev
2022-11-15 16:17   ` [xdp-hints] " Toke Høiland-Jørgensen
2022-11-15 18:37     ` Stanislav Fomichev
2022-11-15 22:46       ` Toke Høiland-Jørgensen
2022-11-16  4:09         ` Stanislav Fomichev
2022-11-16  6:38           ` John Fastabend
2022-11-16  7:47             ` Martin KaFai Lau
2022-11-16 10:08               ` Toke Høiland-Jørgensen
2022-11-16 18:20                 ` Martin KaFai Lau
2022-11-16 19:03                 ` John Fastabend
2022-11-16 20:50                   ` Stanislav Fomichev
2022-11-16 23:47                     ` John Fastabend
2022-11-17  0:19                       ` Stanislav Fomichev
2022-11-17  2:17                         ` Alexei Starovoitov
2022-11-17  2:53                           ` Stanislav Fomichev
2022-11-17  2:59                             ` Alexei Starovoitov
2022-11-17  4:18                               ` Stanislav Fomichev
2022-11-17  6:55                                 ` John Fastabend
2022-11-17 17:51                                   ` Stanislav Fomichev
2022-11-17 19:47                                     ` John Fastabend
2022-11-17 20:17                                       ` Alexei Starovoitov
2022-11-17 11:32                             ` Toke Høiland-Jørgensen
2022-11-17 16:59                               ` Alexei Starovoitov
2022-11-17 17:52                                 ` Stanislav Fomichev
2022-11-17 23:46                                   ` Toke Høiland-Jørgensen
2022-11-18  0:02                                     ` Alexei Starovoitov
2022-11-18  0:29                                       ` Toke Høiland-Jørgensen
2022-11-17 10:27                       ` Toke Høiland-Jørgensen
2022-11-15  3:02 ` [xdp-hints] [PATCH bpf-next 06/11] xdp: Carry over xdp metadata into skb context Stanislav Fomichev
2022-11-15 23:20   ` [xdp-hints] " Toke Høiland-Jørgensen
2022-11-16  3:49     ` Stanislav Fomichev
2022-11-16  9:30       ` Toke Høiland-Jørgensen
2022-11-16  4:40   ` kernel test robot
2022-11-16  7:04   ` Martin KaFai Lau
2022-11-16  9:48     ` Toke Høiland-Jørgensen
2022-11-16 20:51       ` Stanislav Fomichev
2022-11-16 20:51     ` Stanislav Fomichev
2022-11-16  8:22   ` kernel test robot
2022-11-16  9:03   ` kernel test robot
2022-11-16 13:46   ` kernel test robot
2022-11-16 21:12   ` Jakub Kicinski
2022-11-16 21:49     ` Martin KaFai Lau
2022-11-18 14:05   ` Jesper Dangaard Brouer [this message]
2022-11-18 18:18     ` Stanislav Fomichev
2022-11-19 12:31       ` Toke Høiland-Jørgensen
2022-11-21 17:53         ` Stanislav Fomichev
2022-11-21 18:47           ` Jakub Kicinski
2022-11-21 19:41             ` Stanislav Fomichev
2022-11-15  3:02 ` [xdp-hints] [PATCH bpf-next 07/11] selftests/bpf: Verify xdp_metadata xdp->af_xdp path Stanislav Fomichev
2022-11-15  3:02 ` [xdp-hints] [PATCH bpf-next 08/11] selftests/bpf: Verify xdp_metadata xdp->skb path Stanislav Fomichev
2022-11-15  3:02 ` [xdp-hints] [PATCH bpf-next 09/11] mlx4: Introduce mlx4_xdp_buff wrapper for xdp_buff Stanislav Fomichev
2022-11-15  3:02 ` [xdp-hints] [PATCH bpf-next 10/11] mxl4: Support rx timestamp metadata for xdp Stanislav Fomichev
2022-11-15 15:54 ` [xdp-hints] Re: [PATCH bpf-next 00/11] xdp: hints via kfuncs Toke Høiland-Jørgensen
2022-11-15 18:37   ` Stanislav Fomichev
2022-11-15 22:31     ` Toke Høiland-Jørgensen
2022-11-15 22:54     ` Alexei Starovoitov
2022-11-15 23:13       ` Toke Høiland-Jørgensen

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