netdev - Re: [Bug 106241] New: shutdown(3)/close(3) behaviour is incorrect for sockets in accept(3)

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Date:	Thu, 22 Oct 2015 08:15:21 +0200
From:	Casper.Dik@...cle.com
To:	Alan Burlison <Alan.Burlison@...cle.com>
cc:	David Miller <davem@...emloft.net>, viro@...IV.linux.org.uk,
	eric.dumazet@...il.com, stephen@...workplumber.org,
	netdev@...r.kernel.org, dholland-tech@...bsd.org
Subject: Re: [Bug 106241] New: shutdown(3)/close(3) behaviour is incorrect for sockets in accept(3) 


>It's been said that the current mechanisms in Linux & some BSD variants 
>can be subject to races, and the behaviour exhibited doesn't conform to 
>POSIX, for example requiring the use of shutdown() on unconnected 
>sockets because close() doesn't kick off other threads accept()ing on 
>the same fd. I'd be interested to hear if there's a better and more 
>performant way of handling the situation that doesn't involve doing the 
>sort of bookkeeping Casper described,.

Of course, the implementation is now around 18 years old; clearly a lot of 
things have changed since then.

In the particular case of Linux close() on a socket, surely it must be 
possible to detect at close that it is a listening socket and that you are 
about to close the last reference; the kernel could then do the shutdown() 
all by itself.

Casper

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