Re: The dreadful CLOSE_WAIT

[William Lee Irwin III <wli@holomorphy.com>]

On Tue, Jul 27, 2004 at 10:39:47AM +0200, DervishD wrote:
>     Seems under Linux that, when a connection is in the CLOSE_WAIT
> state, the only wait to go to LAST_ACK is the application doing the
> 'shutdown()' or 'close()'. Doesn't seem to be a timeout for that.
>     Well, I think this is dangerous because a bad application (and a
> couple of widely used servers have this problem) can exhaust system
> network resources (difficult, but possible). For example, a
> concurrent FTP server with a race condition that doesn't do the
> shutdown when the remote end aborts. Writing such a 'bad app' is very
> easy, just do the socket->bind->listen->accept and after accepting
> the connection forget the connected socket and keeps on listening. If
> the remote end aborts, the server leaves the connection in
> CLOSE_WAIT. Sometimes it has a associated timer, when data remains in
> the tx queue, it seems that the kernel tries to retransmit all that
> data, which makes no sense: in CLOSE_WAIT state the other end is not
> there... Surely I'm missing a lot :((

Probably best to implement timeouts by hand in your network daemon.


-- wli