usbus seen as network devices

[Stefan Ehmann]

I've noticed that with 9.0-RC1, usbus[0-9] are seen as network interfaces. I 
figured this is need for usbdump to work.
(This isuue has been raised before [1], but no helpful replies were given).

I find this behavior rather annoying:

1)
usbus0 is the default interface (in 8.2, my primary network interface was 
default)
# tcpdump 
tcpdump: WARNING: usbus0: That device doesn't support promiscuous mode
(BIOCPROMISC: Operation not supported)
tcpdump: WARNING: usbus0: no IPv4 address assigned
tcpdump: packet printing is not supported for link type USB: use -w

2)
Various tools (netstat, tcpdump, wireshark, my network monotoring dockapp) now 
list 8 additional interfaces:
# netstat -i
Name    Mtu Network       Address              Ipkts Ierrs Idrop    Opkts 
Oerrs  Coll
usbus     0 <Link#1>                               0     0     0        0     
0     0
usbus     0 <Link#2>                               0     0     0        0     
0     0
...

3)
I can do rather silly things, that at best will do nothing:
# ifconfig usbus0 10.0.0.1
# usbdump -i lo0


Some applications seem to check the link type, so that unsupported interfaces 
are not shown. But the behavior isn't even consistent in the base system:
- ifconfig -a doesn't show usbus interfaces, but lets you happily configure 
  them
- tcpdump -D shows the interfaces, but bails out if you actually start
  capturing
- netstat shows them
- systat -ifstat only lists real interfaces

Do all these applications need to be patched, or can this be fixed in a single 
place (in the kernel)?

Is there a kernel option/sysctl/etc. to disable this behavior? I'm most likely 
not going to need usbdump in the foreseeable future.

[1] http://lists.freebsd.org/pipermail/freebsd-stable/2011-
September/063941.html

-- 
Stefan