Connect direct and fallback

[Brian Candler]

Hi,

I'm looking for a client-side tool which can be used with ProxyCommand and:

- makes a direct connection attempt
- if the connection fails, makes a second attempt via a configured SOCKS 
server
- preferably uses ProxyUseFdpass, so that it gets out of the way once it 
has done its job

Does anyone know if such a thing already exists?  If not, I might try 
knocking something together.

(Idea is to make a direct connection to a host on IPv6 where possible, 
but when connecting from an IPv4-only network fallback to SOCKS)