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

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Date:	Wed, 26 Feb 2014 15:18:00 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: shutdown()'s 'how' parameter doesn't seem to be used correctly

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).

	David

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