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bpf_sk_lookup.remote_port fixes #59

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Closed

bpf_sk_lookup.remote_port fixes #59

wants to merge 4 commits into from

Commits on Feb 22, 2022

  1. adding ci files

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  2. bpf: Fix certain narrow loads with offsets 

    Verifier treats bpf_sk_lookup.remote_port as a 32-bit field for
backward compatibility, regardless of what the uapi headers say.
This field is mapped onto the 16-bit bpf_sk_lookup_kern.sport field.
Therefore, accessing the most significant 16 bits of
bpf_sk_lookup.remote_port must produce 0, which is currently not
the case.

The problem is that narrow loads with offset - commit 46f53a6
("bpf: Allow narrow loads with offset > 0"), don't play nicely with
the masking optimization - commit 2399463 ("bpf: possibly avoid
extra masking for narrower load in verifier"). In particular, when we
suppress extra masking, we suppress shifting as well, which is not
correct.

Fix by moving the masking suppression check to BPF_AND generation.

Fixes: 46f53a6 ("bpf: Allow narrow loads with offset > 0")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
    @iii-i
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  3. bpf: Fix bpf_sk_lookup.remote_port on big-endian 

    On big-endian, the port is available in the second __u16, not the first
one. Therefore, provide a big-endian-specific definition that reflects
that. Also, define remote_port_compat in order to have nicer
architecture-agnostic code in the verifier and in tests.

Fixes: 9a69e2b ("bpf: Make remote_port field in struct bpf_sk_lookup 16-bit wide")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
    @iii-i
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  4. selftests/bpf: Adapt bpf_sk_lookup.remote_port loads 

    - Remove some remote_port tests that are not applicable to u16.
- Use remote_port_compat for backward compatibility tests.
- Add LSB/LSW backward compatibility tests.
- u32 load produces SRC_PORT on both little- and big-endian machines,
  so check just that.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
    @iii-i
    iii-i authored and Nobody committed Feb 22, 2022
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