Problems with proxy connections

[Chris Rapier]

Could someone explain to me how the proxy command regression test works? 
I'm having a problem as it relates to the HPN patch and could use a 
little insight into what is happening in the proxy connections.

The back story is that the HPN patch was failing the regression tests 
when it his the proxy connections. It would just hang because the tcp 
window size that we get when a channel is created was returning 0. That 
set the internal receive buffer to 0 which just hung up everything.

I was able to get around the problem by explicitly testing to see if the 
connection was on a socket with packet_connection_is_on_socket. If its 
false then I return an arbitrary value (in this case 128k). Otherwise I 
return the window size. I don't like this solution though because, even 
though I know it works, I don't know enough to know if its working in 
the right way.

So the question is, what is this connection type and are there any 
thoughts on what the correct value would be to return?