Re: adding if_dev member to struct ifnet

From: Brooks Davis (brooks_at_one-eyed-alien.net)
Date: 09/30/03

  • Next message: Poul-Henning Kamp: "Re: adding if_dev member to struct ifnet" 
    Date: Tue, 30 Sep 2003 10:15:36 -0700
To: Poul-Henning Kamp <phk@phk.freebsd.dk>

    On Tue, Sep 30, 2003 at 09:10:54AM +0200, Poul-Henning Kamp wrote:
    > In message <200309301045.15776.vjardin@wanadoo.fr>, Vincent Jardin writes:
    > >Le Mardi 30 Septembre 2003 03:03, Brooks Davis a écrit :
    > >> [Previously posted to -net in another form.]
    > >>
    > >> I propose to add an if_dev member to struct ifnet. It would be of type
    > >> device_t and be defined to point to the device for the interface or NULL
    > >> if there is no device (or if there was not an easy way to get access to
    > >> one).
    > >>
    > >> This change would codify the the relationship between an interface and
    > >> the underlying physical device. It also would get rid of the existing
    > >> abuses of if_name to look up the driver associated with an interface
    > >> and simplify a number of messy cases in the conversion from if_unit and
    > >> if_name to if_xname.
    > >>
    > >> Does this seem like a reasonable thing to do?
    > >
    > >Yes, if it helps to remove if_name/if_unit, it is a thing to do. Moreover it
    > >sounds a good idea to have the if_dev field into the ifnet structure.
    >
    > Somebody please explain how this would work for non-hardware
    > interfaces like if_loop, if_tun, if_tap etc ?

    if_dev would be NULL when a device_t was not available. Code which used
    this feature would be required to either check that if_dev was non-NULL
    before trying to use it or have special knowldege that it only gets
    called with struct ifnet instances which have a non-NULL if_dev member.
    For instance, driver routines which take a struct ifnet would know that
    they are only called on their own ifnet so they could assume they had
    filled it in.

    -- Brooks 

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