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

[Jeff Layton]

On Sun, 28 Jul 2013 17:36:56 -0700
Richard Sharpe <realrichardsharpe at gmail.com> wrote:

> 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.
> 

Ok, I think I knew that at one point and paged it out. It does make one
wonder why NI_MAXHOST is so big though -- is that for some
internationalization scheme?

-- 
Jeff Layton <jlayton at redhat.com>