Function wait_for_readable

vmm/src/migration_transport.rs:201–246

Wait for `fd` to become readable. In this case, we return true. In case `abort_event` was signaled, return false.

(fd: &impl AsFd, abort_event: &impl AsRawFd)

// Wait for `fd` to become readable. In this case, we return true. In case
// `abort_event` was signaled, return false.
fn wait_for_readable(fd: &impl AsFd, abort_event: &impl AsRawFd) -> Result<bool, io::Error> {
    let fd = fd.as_fd().as_raw_fd();
    let abort_event = abort_event.as_raw_fd();

    let mut poll_fds = [
        libc::pollfd {
            fd: abort_event,
            events: libc::POLLIN,
            revents: 0,
        },
        libc::pollfd {
            fd,
            events: libc::POLLIN,
            revents: 0,
        },
    ];

    loop {
        // SAFETY: This is safe, because the file descriptors are valid and the
        // poll_fds array is properly initialized.
        let ret = unsafe { libc::poll(poll_fds.as_mut_ptr(), poll_fds.len() as libc::nfds_t, -1) };

        if ret >= 0 {
            break;
        }

        let err = io::Error::last_os_error();
        if err.raw_os_error() == Some(libc::EINTR) {
            continue;
        }

        return Err(err);
    }

    if poll_fds[0].revents & libc::POLLIN != 0 {
        return Ok(false);
    }

    if poll_fds[1].revents & libc::POLLIN != 0 {
        return Ok(true);
    }

    Err(io::Error::other(
        "Poll returned, but neither file descriptor is readable?",
    ))
}

/// Struct to keep track of additional connections for receiving VM migration data.
#[derive(Debug)]