[ros-dev] Loopback problem

[art yerkes]

On Tue, 20 Dec 2005 23:45:41 -0500
Phillip Susi <psusi at cfl.rr.com> wrote:

> A correctly implemented TCP stack will keep sending packets as long as 
> there is free space in the window.  If the existing code refuses to send 
> more packets because there is SOME unacknowledged data, but enough room 
> in the window to send more, then it is broken.
> 
> The entire point of having a window is so that the sender can send 
> multiple packets before the first is ACK'd.  Are you sure that the 
> existing code refuses to send even when the window should allow it?  Or 
> is the window just too small?  If so, are you sure it came directly from 
> the bsd stack?  I can not believe that both are true.
> 
> Ge van Geldorp wrote:
> > Although I understand what's wrong, I have a bit of difficulty trying to
> > figure out how to fix it. Attached is a proposed fix, which basically
> > attacks the problem at the sending end by removing the check if the
> > connection is idle or not. With that fix the loop.c program works as I
> > expect and http://www.reactos.org loads in a much more reasonable 2-3 sec in
> > ibrowser. The problem that I have with the fix is that it's a change in code
> > we borrowed from the BSD stack. I can hardly imagine that a piece of
> > software so heavily used as the BSD stack would have such a fundamental
> > problem.
> > 
> > Any thoughts?
> > 
> > GvG
> > 
> 
The problem is likely in our loopback pseudo adapter rather than
the BSD code, I'd guess.

It actually doesn't come directly from BSD.  It was first in oskit,
in which some work was done to isolate a few parts of FreeBSD and 
simplify and generalize the buffer management code.  If there's
a mistake in the TCP implementation itself, I might have introduced
it.  Since the IP and TCP code had stuff that overlaps code we
already had in tcpip.sys, I narrowed the scope of the BSD code
to make the import more compact (and preserve as much original
code as possible in ReactOS).
-- 
Here's a simple experiment. Stand on a train track between two
locomotives which are pushing on you with equal force in opposite
directions. You will exhibit no net motion. None the less, you may
soon begin to notice that something important is happening.
-- Robert Stirniman