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27a0f3635d
test_maps fails in the sockmap test because sockmap_verdict_prog.c
drops the packet when the first 8 bytes are not directly accessible:
if (data + 8 > data_end)
return SK_DROP;
The blamed commit removed bpf_skb_pull_data() from the stream parser
program so that the parser no longer modifies the skb. That was needed,
but it also removed an implicit side effect: bpf_skb_pull_data()
linearized enough of the skb for later direct packet access.
In this test, the send side goes through the sockmap SK_MSG path. The
skb can have skb->len == 20 while its linear area is empty, so the
verdict program sees data == data_end and drops the packet even though
the payload length is sufficient.
Keep the parser read-only, and pull the first 8 bytes in the verdict
program before reading or writing them. Reload data/data_end after
bpf_skb_pull_data() as required.
Fixes: 22a0cc10da ("selftests/bpf: don't modify the skb in the strparser parser prog")
Reported-by: Ihor Solodrai <ihor.solodrai@linux.dev>
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260701071501.39628-1-jiayuan.chen@linux.dev
Closes: https://lore.kernel.org/bpf/e3a91acd-2b4d-4e93-a3bb-a0e9ee5ede0f@linux.dev/