sftp performance problem, cured by TCP_NODELAY

[Miklos Szeredi]

> Better logic to control NODELAY usage makes sense. I never looked 
> closely at this portion of the code but perhaps it could be triggered by 
> a request for remote TTY.

That is what the current code does.  And that is the source of the
bug, since NODELAY is needed for some non-interactive traffic, like
sftp.

> I actually agree with Damien on this point. There shouldn't be a user 
> setting. The software should be able to determine when NODELAY should 
> and shouldn't be set. While it might be more difficult to create a 
> generalized solution because of port fowarding issue a more specific 
> solution that will capture 95% of the common usage situations should be 
> feasible.

Well, currently the software is doing the wrong decision, and I'm not
entirely convinced, that there is any other valid heuristic than to
turn NODELAY on unconditionally.

Miklos