Linux Ethernet Bridging - Jun 2014 - [Bridge] [PATCH net-next] bridge: Fix incorrect judgment of promisc

(2014/06/05 21:55), David Laight wrote:
> 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 at
lab.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
The last line should be set.

Thanks,
Toshiaki Makita
> 
> 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

From: Toshiaki Makita 
> > 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
> 
> The last line should be set.
I've clearly not drunk enough coffee today...

I suspect the 0-1 line is impossible.
Since the check is probably for 'any other ports in 'auto'
mode'.
So:
	if (auto_cnt - auto_port > 0)
(which is much the same as the original) is a good descriptive test.

	David