boost::asio::async_read() of stream_descriptor now returning EOF

Upgraded Ubuntu today from 14.10 to 15.04. Now seeing different behaviour either in boost::asio::async_read(), boost::asio::posix::stream_descriptor, or tap/tun interfaces. Calling async_read() immediately returns boost::asio::error::eof. If I ignore the error and loop back up to start a new async_read() it does eventually read when bytes are available, and the application continues to work.

The problem with doing this workaround loop is the application now consumes 100% of a core as it sits in a tight loop continuously restarting the call to async_read().

This is how I'm setting things up:

fd = open("/dev/net/tun", O_RDWR);
....
boost::asio::posix::stream_descriptor my_stream( io_service);
my_stream.assign(fd, ec);
...
boost::asio::async_read(my_stream, my_buffer, boost::asio::transfer_at_least(16),
    [=](const EC &error, std::size_t bytes_read)
    {
        if (error) // <- this triggers with EOF error