usb/149039: [uhso] Binding problem with uhso

Fredrik Lindberg fli at shapeshifter.se
Mon Aug 2 06:54:39 UTC 2010


On 08/01/2010 04:37 AM, perryh at pluto.rain.com wrote:
>> The following reply was made to PR usb/149039; it has been noted
>> by GNATS.
>>
>> From: Fredrik Lindberg<fli at shapeshifter.se>
>> To: bug-followup at FreeBSD.org, pilzableiter at web.de
>> Cc: Hans Petter Selasky<hselasky at c2i.net>
>> Subject: Re: usb/149039: [uhso] Binding problem with uhso
>> Date: Sat, 31 Jul 2010 15:00:07 +0200
>>
>>   I apparently missed some interface flags (that really doesn't make
>>   sense for this device, it's configured with a /32 mask so broadcast
>>   etc can only be to itself) that the network stack wants to work
>>   properly.
>
> Is a /32 mask even legal?  Unless there's a special case involved,
> it ought to mean that there are no interfaces on the subnet other
> than this one, thus this interface has no peer to communicate with
> and might as well not exist.
>
> Adding net@ in hopes someone there knows what should happen.
>

Yes, technically a /32 mask defines only one single address, but it's
the only mask that really makes sense for this device.  /32 masks are
"legal" and commonly used for the loopback address of routers.

But this is is indeed a very special case.  The device has a
USB interface that accepts raw IP-packets (with no other
encapsulation).  Once you have told the device to connect, it will
tell you what IP-address you have and what DNS-servers to use, but
that's it.  My best guess is that the devices does PPP internally in
firmware and abstracts the point-to-point link with a IP-packet
interface.  But since none of these details are available the only (as
far as I know) viable thing is to set a /32 mask and set 0.0.0.0
(default route) to be directly reachable through the interface (route
add -interface).


Fredrik Lindberg


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