netdev - RE: shutdown()'s 'how' parameter doesn't seem to be used correctly

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6D0F6CBEBC@AcuExch.aculab.com>
Date:	Wed, 26 Feb 2014 17:10:03 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Eric Dumazet' <eric.dumazet@...il.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: shutdown()'s 'how' parameter doesn't seem to be used correctly

From: Eric Dumazet 
> On Wed, 2014-02-26 at 15:18 +0000, David Laight wrote:
> > AFAICT userspace calls shutdown(sock, how) with 'how' set to one of SHUT_RD (0),
> > SHUT_WR (1) or SHUT_RDWR(2).
> >
> > The kernel code typically wants the bitmask of RCV_SHUTDOWN (1) | SEND_SHUTDOWN (2).
> > If you look at the af_unix.c unix_shutdown() there is a comment where it
> > add's one in order to do the conversion.
> >
> > But I can't find the conversion before tcp_shutdown() or sctp_shutdown()
> > checks for 'how & SEND_SHUTDOWN'.
> > Which implies that shutdown(sock, SHUT_WR) doesn't work.
> >
> > What have I missed?
> > Should I be passing 2 or 3 to a direct call to sock->ops->shutdown()?
> > (We currently pass 2 - which does outward disconnect anyway).
> 
> Take a look at inet_shutdown()

Thanks - the lack of 'grep-friendly' structure member names makes
chasing through this code hard work.

	David