How to set tcp params for mio(0.7.0)'s TcpStream

hi
I have see the docs of mio(0.7.0),but not find where has the way set the tcp params,like these:

    set_recv_buffer_size(size:usize)
    set_send_buffer_size(size:usize)
    set_linger(time:Duration)
    set_keepalive(time:Duration)

the standard library's TcpStream has impl net2's TcpStreamExt,so it could set tcp params, and mio(0.6.21) could too.
but mio(0.7.0) could not.
so I have some questions:
1:did I not find the right way in mio(0.7.0)?
2:if mio(0.7.0) really could not set tcp params,because of has not impl net2's TcpStreamExt?
3:if mio(0.7.0) really could not set tcp params, why author delete it(mio(0.6.21) can set)
4.if I wanna set,i must impl TcpStreamExt for mio(0.7.0)'s tcpstream or use mio(0.7.0)'s tcpstream's from_std()?

pray for the answer O^_^O