proxy through a bastion

.ssh/config:

Host dfw
    Hostname cbast.dfw1.example.net
    ForwardAgent yes
    ForwardX11Trusted yes
    ProxyCommand none
    User myusername
    ControlMaster auto
    ControlPath ~/.ssh/master-%r@%h:%p
    TCPKeepAlive yes
    ServerAliveInterval 300

Host *
    ProxyCommand ssh dfw nc %h %p 2> /dev/null
    ForwardAgent yes
    ForwardX11 no
    GSSAPIAuthentication no
    VerifyHostKeyDNS no
    HashKnownHosts no
    TCPKeepAlive yes
    ServerAliveInterval 300