[e2e] Is this a bug with Windows TCP Stack ?

[sanjay kaniyar]

Tommy,

A Shutdown(SD_SEND) followed by a Close() results in a RST only when there 
is unacknowledged data or FIN on the connection in that direction. 
Otherwise, a Close() just releases the local system resources for that 
connection.

The semantics of Windows sockets implementation for Shutdown() is detailed 
at: 
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winsock/winsock/shutdown_2.asp

Most of it is similar to what you described below.

Thanks,
Sanjay

>From: Tommy Marcus McGuire <mcguire at cs.utexas.edu>
>To: end2end-interest at postel.org
>Subject: Re: [e2e] Is this a bug with Windows TCP Stack ?
>Date: Fri, 10 Dec 2004 16:40:51 -0600
>
>I've seen comments about shutdown() like Sanjay's before, and either I
>don't understand the comments, or the use of shutdown().
>
>I've only used shutdown() to close half of the two-way connection,
>either to indicate that I'm not writing anything more on it (Which will
>result in an end-of-file condition when the FIN gets to the receiver.)
>or to indicate that my end is not going to be reading anything (Which is
>rare; I'm not sure what would happen if the other end of the connection
>tried to write to it.  A RST maybe?).
>
>If I don't care about the connection at all, I call close() and forget
>about it.  If the other side wants to write to the connection, it will
>get a RST, but that's not my problem.  If the other side is still
>reading, it will get the FIN.  The TCP stack on the local machine should
>handle the wait states just fine.
>
>What I've seen (and interpret Sanjay's comments below to mean) is advice
>to use shutdown() (for both halves of the connection) and then close(),
>which doesn't make sense---the close() should report a local error
>since the shutdown has already done everything the close would do.  Is
>a close() on a previously-shutdown() connection supposed to generate a
>RST?  If so, why?  Like Joe said, there's no error here.
>
>On Wed, Dec 08, 2004 at 09:16:13PM -0800, Joe Touch wrote:
> > sanjay kaniyar wrote:
> > >RST is sent out because the application does not care about the 
>connection
> > >anymore.
> >
> > "not care" is not an error.
> >
> > RST is supposed to go out only for a transport protocol error or an
> > application ABORT. Abort doesn't carry the 'I don't care' semantics;
> > it's deliberate blowing away of state, and should be used with caution, 
>IMO.
> >
> > >For instance, say an application sent data, issued a Shutdown() to
> > >close the connection gracefully - it waits for a duration of its choice 
>but
> > >the disconnect does not complete and it wants to abort the connection. 
>The
> > >Close() enables the application do exactly that.
> >
> > Why does it need to abort the connection? If the disconnect doesn't
> > complete, the CLOSE should resend the FIN. If the FIN arrives and a RST
> > is sent in response, so be it, but that's what would happen - not the
> > other way around.
> >
> > Besides, disconnect only means "I have nothing more to send" - closes
> > are half-closes, not full, in TCP. If what you wanted was "close both
> > ends", you are better off picking (or designing) another protocol,
> > rather than abusing TCP.
>
>
>--
>Tommy McGuire