[PATCH 2/2] cifs: Correct comment about domainname length

[Richard Sharpe]

On Sun, Jul 28, 2013 at 5:27 PM, Chen Gang <gang.chen at asianux.com> wrote:
> On 07/27/2013 02:12 AM, Scott Lovenberg wrote:
>> On Thu, Jul 25, 2013 at 8:40 PM, Chen Gang <gang.chen at asianux.com> wrote:
>>> On 07/26/2013 02:34 AM, scott.lovenberg at gmail.com wrote:
>>>> From: Scott Lovenberg <scott.lovenberg at gmail.com>
>>>>
>>>> CIFS_MAX_DOMAINNAME_LEN is the max length for a domain name, not a fully qualified domain name.
>>>>
>>>> Signed-off-by: Scott Lovenberg <scott.lovenberg at gmail.com>
>>>> ---
>>>>  include/uapi/linux/cifs/cifs_mount.h | 2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/include/uapi/linux/cifs/cifs_mount.h b/include/uapi/linux/cifs/cifs_mount.h
>>>> index a58fc6e..d2408ec 100644
>>>> --- a/include/uapi/linux/cifs/cifs_mount.h
>>>> +++ b/include/uapi/linux/cifs/cifs_mount.h
>>>> @@ -17,7 +17,7 @@
>>>>  #define _CIFS_MOUNT_H
>>>>
>>>>  /* Max string lengths for cifs mounting options. */
>>>> -#define CIFS_MAX_DOMAINNAME_LEN 256 /* max fully qualified domain name */
>>>> +#define CIFS_MAX_DOMAINNAME_LEN 256 /* max domain name length */
>>>>  #define CIFS_MAX_USERNAME_LEN   256 /* reasonable max for current servers */
>>>>  #define CIFS_MAX_PASSWORD_LEN   512 /* Windows max seems to be 256 wide chars */
>>>>  #define CIFS_MAX_SHARE_LEN      256 /* reasonable max share name length */
>>>>
>>>
>>> For our kernel implementation:
>>>
>>>   for 'CIFS_MAX_DOMAINNAME_LEN', it counts 255 + '\0',
>>>   for 'CIFS_MAX_USERNAME_LEN', it counts 256 (may add additional '\0'),
>>>
>>> And original mail said about 'CIFS_MAX_DOMAINNAME_LEN':
>>>
>>>   "The maximum length of ... the fully qualified domain name (FQDN) is
>>>   63 octets per label and 255 bytes per FQDN. This maximum includes 254
>>>   bytes for the FQDN and one byte for the ending dot."
>>>
>>> And excuse me, I do not know what 'CIFS_MAX_USERNAME_LEN' should be.
>>>
>>> Do we also need consider about it in our definition comments ?
>>>
>>>
>>> Thanks.
>>> --
>>> Chen Gang
>>
>> Sorry, I misunderstood; I figured that it had to be the domain name
>> without the host since we were allowing a host name that's 1024
>> characters long.  That documentation should probably be added to the
>> cifs_mount.h as well then.
>>
>> Still, how can we have a FQDN that's 256 characters long when the host
>> name length can be 1024 characters long?
>>
>
> Excuse me, I am not quite familiar about cifs, so can not provide
> additional more information (I found it only by reading code).
>
> But I feel, it really need additional discussion and check by the
> related experts (related members who are familiar with cifs).
>
> Welcome any members' suggestions and completions.
>
> Thanks.

Come on guys, enough already. As per here:
https://en.wikipedia.org/wiki/Domain_Name_System

and a comment above the max len of the fully qualified domain name (FQDN) is
63 octets per label and 255 bytes per FQDN. This maximum includes 254
bytes for the FQDN and one byte for the ending dot.

-- 
Regards,
Richard Sharpe
(何以解憂？唯有杜康。--曹操)