make testsuite pass on bigendian

[alexanderkjall]

I'm not the original author, but the patch is placed under the MIT license per: https://salsa.debian.org/rust-team/debcargo-conf/-/blob/master/src/netlink-sys/debian/copyright?ref_type=heads#L10

Original commit message from https://salsa.debian.org/rust-team/debcargo-conf/-/blob/master/src/netlink-sys/debian/patches/bigendian.patch?ref_type=heads

This patch makes the autopkgtests pass on bigendian, it's still far from ideal
but it's an improvement over the situation in testing at the time of writing.

Two tests are addressed, mio::tests::test_event_loop and socket::test::options

I have no clue what is causing test_event_loop to fail so I have simply skipped
that for now.

socket::test::options failed because of what appears to be a kernel issue,
according to the documentation the options are of type int, but retrieving them
seems to retrieve only a single byte. On little endian this byte is placed in
the LSB resulting in 1 for true and 0 for false, but on big endian it is placed
in the MSB resulting in 0x01000000 for true and 0 for false. This patch changes
the comparisions from == 1 to != 0 so they work on both big and little endian.

Author: Peter Michel Green plugwash@debian.org

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request aims to improve the compatibility of the test suite with big-endian systems. It specifically addresses two failing tests by temporarily disabling one on big-endian and correcting boolean value comparisons in another to ensure consistent behavior across different endian architectures.

Highlights

• Test Suite Compatibility: The pull request addresses issues preventing the test suite from passing on big-endian systems, specifically targeting two failing tests.
• mio::tests::test_event_loop: The mio::tests::test_event_loop test is now conditionally compiled to run only on little-endian systems, as its failure cause on big-endian is currently unknown.
• socket::test::options: Comparisons for socket options in socket::test::options were updated from == 1 to != 0 to correctly handle boolean values on both big-endian and little-endian architectures, resolving an issue where a single byte value was misinterpreted due to endianness.

Changelog

• src/mio.rs
  • Added #[cfg(target_endian = "little")] to the tests module to skip mio::tests::test_event_loop on big-endian systems.
• src/socket.rs
  • Modified several Ok(res == 1) expressions to Ok(res != 0) when checking socket option return values, to correctly interpret boolean results regardless of system endianness.

Activity

• No explicit activity (comments, reviews, or progress updates) was provided in the context.

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[gemini-code-assist]

Code Review

This pull request aims to make the test suite pass on big-endian systems. The changes in src/socket.rs correctly fix boolean checks to be endian-agnostic by changing == 1 to != 0, which is a good improvement. However, the change in src/mio.rs disables a test on big-endian systems. I've provided a suggestion to fix the test instead of disabling it, which would be a more robust solution.

[gemini-code-assist]

While disabling this test module on big-endian systems makes the test suite pass, it hides an underlying issue and reduces test coverage. The problem is that the hardcoded netlink message in request_neighbour_dump is little-endian specific, which causes the test to fail on big-endian architectures.

A better approach would be to make the test endian-agnostic by constructing the message at runtime. This would fix the test on big-endian systems and restore test coverage.

Here is a suggested implementation for request_neighbour_dump that should work on all platforms:

fn request_neighbour_dump(socket: &mut Socket) -> std::io::Result<()> {
    let mut buf = [0u8; 28];
    // nl_msglen = 28
    buf[0..4].copy_from_slice(&28u32.to_ne_bytes());
    // nl_msgtype = 30 (RTM_GETNEIGH)
    buf[4..6].copy_from_slice(&30u16.to_ne_bytes());
    // nl_msgflags = NLM_F_REQUEST | NLM_F_DUMP = 0x0301
    buf[6..8].copy_from_slice(&0x0301u16.to_ne_bytes());
    // The rest is zeroed out, which is fine for seq, pid, and payload for this request.
    socket.send(&buf[..], 0)?;

    Ok(())
}

With this change, you can remove the #[cfg(target_endian = "little")] attribute.

[cathay4t]

Thanks for the patch! Could you also comment your finding on big-endian issue in #4 where we may continue the investigation?