netdev - RE: [PATCH net-next] bridge: Fix incorrect judgment of promisc

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Date:	Thu, 5 Jun 2014 12:55:59 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Toshiaki Makita' <makita.toshiaki@....ntt.co.jp>,
	"David S . Miller" <davem@...emloft.net>,
	Stephen Hemminger <stephen@...workplumber.org>
CC:	Vlad Yasevich <vyasevic@...hat.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"bridge@...ts.linux-foundation.org" 
	<bridge@...ts.linux-foundation.org>
Subject: RE: [PATCH net-next] bridge: Fix incorrect judgment of promisc

From: Toshiaki Makita
> (2014/06/05 20:03), David Laight wrote:
> > From: Toshiaki Makita
> >> br_manage_promisc() incorrectly expects br_auto_port() to return only 0
> >> or 1, while it actually returns flags, i.e., a subset of BR_AUTO_MASK.
> >>
> >> Signed-off-by: Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
> >> ---
> >>  net/bridge/br_if.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
> >> index a08d2b8..6a07a40 100644
> >> --- a/net/bridge/br_if.c
> >> +++ b/net/bridge/br_if.c
> >> @@ -153,7 +153,7 @@ void br_manage_promisc(struct net_bridge *br)
> >>  			 * This lets us disable promiscuous mode and write
> >>  			 * this config to hw.
> >>  			 */
> >> -			if (br->auto_cnt <= br_auto_port(p))
> >> +			if (br->auto_cnt <= !!br_auto_port(p))
> >>  				br_port_clear_promisc(p);
> >>  			else
> >>  				br_port_set_promisc(p);
> >
> > Why not the less confusing:
> > 			if (br->auto_cnt || br_auto_port(p))
> > and reverse the then/else lines?
> 
> I'm respecting the original style, but I'm not particular about this style.
> I'll make less confusing one, thanks :)
> 
> (Your suggested condition is not exactly the same as current one, even
> if reversing if/else. v2 will be different than it. Anyway, thanks.)

A quick truth table:
	auto_cnt	auto_port	set/clear
		0		0	clear
		0		1	clear
		1		0	set
		1		1	clear
		2+		0/1	clear

So you want:
	if (br->auto_cnt && !br_auto_port(p))
		br_port_set_promisc(p);
	else
		br_port_clear_promisc(p);

Does seem like a strange condition.

	David

	


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