[Ns-bugs] [Bug 424] TCP FIN notification callback needed

[code@nsnam.ece.gatech.edu]

http://www.nsnam.org/bugzilla/show_bug.cgi?id=424





--- Comment #5 from Tom Henderson <tomh at tomh.org>  2009-03-18 10:04:55 EDT ---
(In reply to comment #2)
> The inline docs say:
> 
> """Sets the "close" callback, which is a notification
> that the other end of the connection has sent a message
> indicating that it will not send any more data, i.e.
> the socket is closed for reading."""
> 
> While this may be true, I think it's even more important to note that, when the
> close callback is invoked we have a guaranteed that all data _we transmitted_
> has been flushed and acknowledged by the receiver.

If we want to be able to convey that all data we transmitted has been
successfully sent, we could do two things that should cover most cases:

- provide some equivalent to SO_LINGER socket option, with a callback for
notifying the application that close() would have returned, for apps that use
close() after write()
- suggest to users the following socket call sequence:

Set the close callback
when done writing, call ShutdownSend()
wait for NotifyClose()
then call Close()

as in:
http://blog.netherlabs.nl/articles/2009/01/18/the-ultimate-so_linger-page-or-why-is-my-tcp-not-reliable

we should also make sure that there is a means to reliably detect when the peer
has sent a RST


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