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* [BUG?] xdp-loader unable to load XDP program with bpf_xdp_adjust_meta() call
@ 2025-05-15 13:09 Vincent Li
  0 siblings, 0 replies; only message in thread
From: Vincent Li @ 2025-05-15 13:09 UTC (permalink / raw)
  To: bpf, Eduard Zingerman, Toke Høiland-Jørgensen

Hi,

We have run into issue reported in [0] when the XDP program has calls like:

bpf_xdp_adjust_meta(ctx, -(int)sizeof(struct meta_data))
or
bpf_xdp_adjust_tail(ctx, -1) < 0

xdp-loader is unable to load these XDP programs with verifier error
message "Extension program changes packet data, while original does
not", it seems to be triggered by the patches [1], removing these
calls work around the issue. it appears  another workaround is to
bpf_xdp_adjust_meta(ctx, 0) after reading [1] thread?

[0]: https://github.com/xdp-project/xdp-tools/issues/503
[1]: https://lore.kernel.org/all/20241210041100.1898468-1-eddyz87@gmail.com/

Vincent

Thanks!

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2025-05-15 13:09 [BUG?] xdp-loader unable to load XDP program with bpf_xdp_adjust_meta() call Vincent Li

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