Re: [Bluez-users] Adresse resolution in BlueZ

[BZ Benny <bennybbz@yahoo.fr>]

Hi Marcel,

Excuse me if I wasn't precise.

I know that the BD_ADDR is the MAC address it is
explained in the BNEP spec. and when I do ifconfig
bnep0 i see in the MAC address feild the BD_ADDR.

When we conect tow bluetooth devices with a PAN
connection, we use ifconfig to affect an IP address
for both our PC.

The IP address is in the IP layer.When the tcp stack
send an IP frame in the IP headers we find the IP
address of the sender and the IP address of the dst.

when BNEP receive this IP frame it needs to build its
BNEP headers. The BNEP header cantains (not in
ETHERNET_COMPRESSED) the BD_ADDR of the dst and the
src. BNEP needs to convert the IP address into
BD_ADDR.

So BNEP ask IP for such a thing. This BD_ADDR is
stored in an ARP table. the ARP table is in the IP
layer. The ARP table contains for any known IP address
its related BD_ADDR (or MAC address as you want).

If this IP isn't known like when we begin a conection
the IP layer send an ARP resolution request asking
which device owns this IP address. The device it have
this IP address reply with " this Ip address is owne
by this BD_ADDR"
so the IP layer store this BD_ADRR in this ARP table.

you can see that with #tcpdump -i bnep0.

The ARP protocol is explained here. 
http://www.ietf.org/rfc/rfc826.txt.

Actually this is the protocol between the IP layer and
the Ethernet layer. Since the BNEP have to replace the
Ethernet layer, I wanted to know how is implemented
address resolution in BNEP. Exactly how BNEP ask IP
for getting the BD_ADDR stored in the ARP table. 

regards
Benny



--- Marcel Holtmann <marcel@holtmann.org> wrote:
> Hi Benny,
> 
> > But, How could bnep build its bnep frame. BNEP
> receive
> > frome TCP/IP the IP address of the peer device.
> And
> > she needs to convert this IP adresse into a MAC
> > address so it needs to ask for the MAC adresse in
> the
> > ARP tables in the IP layer.
> > isn't it?
> 
> the MAC address of the virtual network card is the
> BD_ADDR. Both are
> part of the IEEE address range and they will never
> overlap.
> 
> Regards
> 
> Marcel
> 
> 
> 
> 
>
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