feat: add rdma_reject, rdma_get_devices and address getters

[dragonJACson]

No description provided.

[gemini-code-assist]

Code Review

This pull request adds support for rejecting connections, querying RDMA devices, and retrieving local and remote ports and socket addresses from an Identifier. The review feedback highlights several critical compilation issues, including calls to an undefined helper function port_from_raw_addr in tests, and incorrect pointer usage (self.cm_id.as_ref() instead of self.cm_id.as_ptr()) when calling FFI functions. Additionally, the get_devices function needs to be updated to correctly handle cases where no RDMA devices are present on the system without returning an error.

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[gemini-code-assist]

If there are no RDMA devices on the system, rdma_get_devices returns NULL and sets num_devices to 0. Currently, this function treats any NULL return as an error, which will cause a false positive error when no devices are present. Instead, check if num_devices is 0 when devices is NULL and return an empty Vec in that case.

pub fn get_devices() -> Result<Vec<Arc<DeviceContext>>, GetDevicesError> {
    let mut num_devices = 0;
    let devices = unsafe { rdma_get_devices(&mut num_devices) };
    if devices.is_null() {
        if num_devices == 0 {
            return Ok(Vec::new());
        }
        return Err(GetDevicesErrorKind::Rdmacm(io::Error::last_os_error()).into());
    }
    let devices = RdmaDeviceList { devices: unsafe { NonNull::new_unchecked(devices) } };
    let num_devices = usize::try_from(num_devices).map_err(|_| GetDevicesErrorKind::InvalidDeviceCount(num_devices))?;

    let contexts = unsafe { std::slice::from_raw_parts(devices.devices.as_ptr(), num_devices) };
    contexts
        .iter()
        .enumerate()
        .map(|(index, &context)| {
            NonNull::new(context)
                .map(cached_device_context)
                .ok_or_else(|| GetDevicesErrorKind::NullDeviceContext(index).into())
        })
        .collect()
}

[codecov]

Codecov Report

❌ Patch coverage is 73.91304% with 36 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/rdmacm/communication_manager.rs	73.91%	36 Missing ⚠️

Files with missing lines	Coverage Δ
src/rdmacm/communication_manager.rs	84.89% <73.91%> (-2.67%)	⬇️

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[Copilot]

Pull request overview

This PR expands the RDMA CM wrapper API by adding connection rejection support, device enumeration via RDMA CM, and convenient accessors for local/peer addresses and ports, while reusing the existing global DeviceContext cache.

Changes:

• Add Identifier::reject() wrapping rdma_reject, with a dedicated RejectError.
• Add get_devices() wrapping rdma_get_devices and integrating results with the global DeviceContext cache.
• Add Identifier getters for local/peer SocketAddr and for src/dst ports; update/add tests to cover new helpers and improve robustness.

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