Re: virtual wireless interfaces / WDS

On Wed, Apr 16, 2003 at 11:48:16PM -0400, Miles Nordin wrote:
> >>>>> "mwl" == M Warner Losh <[email protected]> writes:
> >>>>> "dy" == David Young <[email protected]> writes:
> 
>    mwl> one doesn't create a virtual interface for every host
>    mwl> on your wired network, so I'm torn.
> 
> I think it is the correct level of complexity.  The status-quo
> alternative is that a simple crippled version of bridge(4) is
> re-implemented inside the hostap code.  This design decision, whether
> it is a decision of 802.11 or a decision of wi(4), causes some
> problems, for example that attaching a bridge(4) between a
> station-mode radio and an Ethernet doesn't work.

  I agree that it is the correct level of complexity.  However, I am not
  sure what you are saying in the last sentence.  An AP can bridge to an
  ethernet, however, its clients *cannot* behave as bridges. This is not
  a constraint of wi(4) or the BSD 802.11 framework, but a constraint
  that the 802.11 committee gave to us. Maybe you are talking about
  something else, though.

> one of the annoying things with dynamically appearing and disappearing
> BSD devices is, if sta147 appears, disappears, and reappears, you
> don't know if it's the same sta147, it's a different sta147, or you
> don't know if it's the same or different.

  I can see how this could be a problem, especially if OSPF or some
  other "wire" routing daemon runs on the stas.

  Certainly AP flags should control whether or not an AP auto-creates
  and auto-deletes stas at all. But it seems necessary to indicate
  associations/discassociations without creating/deleting interfaces.
  An AP can control several of a sta's status variables, including media
  status (active/inactive) and flags (IFF_UP). I favor using the media
  status to indicate associations/disassociations.  (I don't think that
  a routing socket indicates changes in media status with RTM_IFINFO yet,
  but it should: for example, I think that a router should at least have
  an opportunity to make a routing decision at the instant I plug/unplug
  an ethernet cable.)

  On a related note, I think that sometimes it will be desirable to
  pre-create a sta, assign it an IP, attach it to an AP, and pre-assign it
  the MAC of some STA that will associate later.  I think this will suit
  for "pre-authentication" and rapid AP-to-AP hand-offs of roaming STAs.

>     dy> if the wi(4) belongs to a bridge, it should add all of its sta
>     dy> to the bridge?
> 
> Does the abstraction support hostap drivers that can create more than
> one nwid, setting different parameters, and IP addresses, for each?  
> 
> That is a nice thing to do in many situations.  and it's better to do
> it with one card not just to save money, because then the vhostaps
> might be smart enough not to interfere among themselves by two of them
> transmitting or granting voice to two stations in the same interval.

  Do you mean a single radio that is master of more than one BSS at
  once? If we ever see hardware that will support that, I think that
  each such virtual AP deserves its own interface.

Dave

-- 
David Young             OJC Technologies
[email protected]      Urbana, IL * (217) 278-3933
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