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

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

[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@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);
-- 
1.8.1.2

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

[David Laight]

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@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?

	David

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

[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@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.)

Toshiaki Makita

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

[David Laight]

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@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

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

	

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

[Toshiaki Makita]

(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@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

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

[David Laight]

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

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

[Vlad Yasevich]

On 06/05/2014 08:55 AM, 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@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
               Can't happen

> 		1		0	set
              Can't happen
> 		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);

Some versions of the series that added this had
an explicit check for count.  Essentially, the
expanded condition is this:

  if (count == 0)
     clear
  else if (count == 1 && auto_port(p))
     clear
  else
     set

The suggestion was that we could use a boolean (0|1)
to check reduce the above to
  if (count <= auto_port(p))
     clear
  else
     set

Personally, I prefer the extended version since it
is much clearer and is easy to understand.

-vlad

> 
> Does seem like a strange condition.
> 
> 	David
> 
> 	
> 
> 
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