netdev - Re: [PATCH bpf-next v4 0/6] Add kfunc bpf_xdp_pull

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Message-ID: <bb70ed5e-48cb-41e2-921f-591fd619f304@gmail.com>
Date: Fri, 19 Sep 2025 11:13:08 -0700
From: Amery Hung <ameryhung@...il.com>
To: bpf@...r.kernel.org
Cc: netdev@...r.kernel.org, alexei.starovoitov@...il.com, andrii@...nel.org,
 daniel@...earbox.net, paul.chaignon@...il.com, kuba@...nel.org,
 stfomichev@...il.com, martin.lau@...nel.org, mohsin.bashr@...il.com,
 noren@...dia.com, dtatulea@...dia.com, saeedm@...dia.com, tariqt@...dia.com,
 mbloch@...dia.com, maciej.fijalkowski@...el.com, kernel-team@...a.com
Subject: Re: [PATCH bpf-next v4 0/6] Add kfunc bpf_xdp_pull_data



On 9/19/25 11:09 AM, Amery Hung wrote:

I sent the wrong one. I will resend v5. Sorry for spamming the list...

> v3 -> v4
>    patch 2
>    - Improve comments (Jakub)
>    - Drop new_end and len_free to simplify code (Jakub)
>
>    patch 4
>    - Instead of adding is_xdp to bpf_test_init, move lower-bound check
>      of user_size to callers (Martin)
>    - Simplify linear data size calculation (Martin)
>
>    patch 5
>    - Add static function identifier (Martin)
>    - Free calloc-ed buf (Martin)
>
> v2 -> v3
>    Separate mlx5 fixes from the patchset
>
>    patch 2
>    - Use headroom for pulling data by shifting metadata and data down
>      (Jakub)
>    - Drop the flags argument (Martin)
>
>    patch 4
>    - Support empty linear xdp data for BPF_PROG_TEST_RUN
>
>    Link: https://lore.kernel.org/bpf/20250915224801.2961360-1-ameryhung@gmail.com/
>
> v1 -> v2
>    Rebase onto bpf-next
>
>    Try to build on top of the mlx5 patchset that avoids copying payload
>    to linear part by Christoph but got a kernel panic. Will rebase on
>    that patchset if it got merged first, or separate the mlx5 fix
>    from this set.
>
>    patch 1
>    - Remove the unnecessary head frag search (Dragos)
>    - Rewind the end frag pointer to simplify the change (Dragos)
>    - Rewind the end frag pointer and recalculate truesize only when the
>      number of frags changed (Dragos)
>
>    patch 3
>    - Fix len == zero behavior. To mirror bpf_skb_pull_data() correctly,
>      the kfunc should do nothing (Stanislav)
>    - Fix a pointer wrap around bug (Jakub)
>    - Use memmove() when moving sinfo->frags (Jakub)
>
>    Link: https://lore.kernel.org/bpf/20250905173352.3759457-1-ameryhung@gmail.com/
>    
> ---
>
> Hi all,
>
> This patchset introduces a new kfunc bpf_xdp_pull_data() to allow
> pulling nonlinear xdp data. This may be useful when a driver places
> headers in fragments. When an xdp program would like to keep parsing
> packet headers using direct packet access, it can call
> bpf_xdp_pull_data() to make the header available in the linear data
> area. The kfunc can also be used to decapsulate the header in the
> nonlinear data, as currently there is no easy way to do this.
>
> Tested with the added bpf selftest using bpf test_run and also on
> mlx5 with the tools/testing/selftests/drivers/net/{xdp.py, ping.py}.
> mlx5 with striding RQ enabled always passse xdp_buff with empty linear
> data to xdp programs. xdp.test_xdp_native_pass_mb would fail to parse
> the header before this patchset.
>
> Thanks!
> Amery
>
> Amery Hung (6):
>    bpf: Allow bpf_xdp_shrink_data to shrink a frag from head and tail
>    bpf: Support pulling non-linear xdp data
>    bpf: Clear packet pointers after changing packet data in kfuncs
>    bpf: Support specifying linear xdp packet data size for
>      BPF_PROG_TEST_RUN
>    selftests/bpf: Test bpf_xdp_pull_data
>    selftests: drv-net: Pull data before parsing headers
>
>   include/net/xdp_sock_drv.h                    |  21 ++-
>   kernel/bpf/verifier.c                         |  13 ++
>   net/bpf/test_run.c                            |   9 +-
>   net/core/filter.c                             | 119 ++++++++++--
>   .../bpf/prog_tests/xdp_context_test_run.c     |   4 +-
>   .../selftests/bpf/prog_tests/xdp_pull_data.c  | 176 ++++++++++++++++++
>   .../selftests/bpf/progs/test_xdp_pull_data.c  |  48 +++++
>   .../selftests/net/lib/xdp_native.bpf.c        |  89 +++++++--
>   8 files changed, 445 insertions(+), 34 deletions(-)
>   create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_pull_data.c
>   create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_pull_data.c
>