Re: pathnames

From: Douglas Kilpatrick (dougkat_private)
Date: Fri Jun 29 2001 - 07:59:39 PDT

  • Next message: James Morris: "Networking hooks"

    On Fri, 29 Jun 2001, Serge E. Hallyn wrote:
    
    > Of course, if we ask to modify the vfsmount structure, we may be
    > asking too much.  But if we can't do that, then perhaps we *should*
    > remove the other pathname-based label assignment functions, in order
    > to give the rest of lsm a better chance.  Naturally, that is not my
    > preference.
    
    My take, as the guy who uses pathnames, but feels they are still the
    "Wrong Answer"(tm).
    
    IMHO, the 'Correct Answer' is to have an initialization stage that
    applies types to files via some kind of Extended Attribute mechanism.
    Your enforcement layer should only care about types, and basically
    ignore filenames.
    
      Yes, I know EA's don't exist yet.  I'm talking theory here, lets not
      add in any annoying facts to slow things down.
    
    A very good point was raised last night at the BOF about trying to
    type files that do not yet exist.  Apparently our DTE system hit
    similar problems and the hack-around they used may work.
    
    They used something they called "HADB" for Heirachical Attribute
    DataBase.  Basically they kept a whole shadow tree of inodes in which
    they kept types, and while most of the shadow inodes refered to real
    inodes, they did not have to.
    
    So basically, You could add into your opaque security structure on the
    inode a tree to represent the children that do not yet exist that you
    want mappings for.  At creation time you can look at the realitive
    name only to determine if this object is one you care about and assign
    your type tags.
    
    (For removing objects, a "is same type" test could be used to let you
    know if you have to re-create the shadow tree...)
    
    
    Questions? (I don't know if I can answer any, but that has never
    prevented me from making up things in the past)  Comments?
    
    
    Doug
    -- 
    dougkat_private
    dkilpatrat_private
    
    
    
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