Re: [PATCH] sctp: fix Kconfig bug in default cookie hmac selection

[Alex Elder <elder@inktank.com>]

On 01/07/2013 11:41 AM, Neil Horman wrote:
> On Mon, Jan 07, 2013 at 10:47:46AM -0600, Alex Elder wrote:
>> The following commit added a "choice" to the sctp Kconfig file.  It
>> introduced a bug which led to an infinite loop when while running
>> "make oldconfig".
>>
>>     0d0863b0 sctp: Change defaults on cookie hmac selection
>>
>> The problem is that the wrong symbol was defined as the default
>> value for the choice.  Using the correct value gets rid of the
>> infinite loop.
>>
>> Note:  if CONFIG_SCTP_COOKIE_HMAC_SHA1=y was present in the input
>> config file, both that and CONFIG_SCTP_COOKIE_HMAC_MD5=y be present
>> in the generated config file.
>>
>> Signed-off-by: Alex Elder <elder@inktank.com>
>> ---
>>  net/sctp/Kconfig |    2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/sctp/Kconfig b/net/sctp/Kconfig
>> index c262106..7521d94 100644
>> --- a/net/sctp/Kconfig
>> +++ b/net/sctp/Kconfig
>> @@ -68,7 +68,7 @@ config SCTP_DBG_OBJCNT
>>  	  If unsure, say N
>>  choice
>>  	prompt "Default SCTP cookie HMAC encoding"
>> -	default SCTP_COOKIE_HMAC_MD5
>> +	default SCTP_DEFAULT_COOKIE_HMAC_MD5
>>  	help
>>  	  This option sets the default sctp cookie hmac algorithm
>>  	  when in doubt select 'md5'
>> -- 
>> 1.7.9.5
>>
>>
> I really, _really_ don't like this.  This does exactly what I was talking about
> before, in that it resolves the loop, but it does so by silently overriding the
> pre-existing configuration, which I think is wrong.  Vlad and I have discussed

I know, that's why I mentioned it explicitly in my explanation.

I experiemented with "optional" but it didn't do the right thing
either.

> it though, and he's convinced me that, despite the silent override, the rest of
> the kernel behaves the same arguably broken way, so we may as well have this

Yup, I checked that too.  It's risky, but at the moment, it
will have no adverse affect on the how the code functions.

> operate in the same way.  I would really far prefer that the config looped to
> make you select a default that was't in conflict with your existing config, but
> I guess those who care to select non-deafult options will catch the change
> anyway, and if you just hit enter, you have to expect changes.
>
> Acked-by: Neil Horman <nhorman@tuxriver.com>

Thanks a lot.

					-Alex