[Netkit.users] Using the mac80211_hwsim to introduce wireless links in Netkit

Massimo Rimondini rimondin at dia.uniroma3.it
Fri Jan 15 10:53:16 CET 2010

Hi Saverio,

as far as I can see, UML is designed to support different transports for
ethernet interfaces only (see, e.g.,
http://lxr.linux.no/#linux+v2.6.26.5/arch/um/drivers/net_kern.c#L392). A
"transport" is a set of data structures and functions that the kernel
uses to communicate with the host. For example, part of the
implementation of the "daemon" transport (that supports virtual hubs) is
here: http://lxr.linux.no/#linux+v2.6.26.5/arch/um/drivers/daemon_kern.c.

My feeling is therefore that things may not be as simple as hacking a
kernel command line, but rather some changes in the mac80211 module
would be required to obtain similar functionality to that of ethernet
interfaces. After all, also the difference in the format of 802.11
frames may call for this requirement.

But there are just wild guesses ;-)


ZioPRoTo (Saverio Proto) wrote:
> Hello,
> I just discovered this recent module for the Linux Kernel:
> http://linuxwireless.org/en/users/Drivers/mac80211_hwsim (read the
> page before reading the rest of this email)
> Now this module goal seems to work on a SINGLE machine, creating many
> virtual interfaces and routing frames to and from these virtual
> interfaces depending on the radio settings ...
> But... do you think it is feasible to attach a collision domain to
> this kind of virtual devices ? Instead of routing the packers just
> inside the mac80211_hwsim module I need to understand if there is a
> way to push packets to a vhub...
> When netkit launchs the UML kernel with vstart something like this is
> added as kernel option:
> so ethX are virtual interfaces for the UML kernel to be attached to
> the vhub... but as for the tap interface... there is some special
> trick to do the job and use the mac8011_hwsim ?
> Sorry if this email sounds a bit confused... but actually I am :)
> Saverio
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