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 <[email protected]> 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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Hi Benny,
> 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.
you like to see a problem where there is no problem. This BNEP virtual
network card is as dumb as a normal Ethernet network card. The network
layer knows our MAC address (BD_ADDR) and if you set the IP to the bnep0
interface, the kernel TCP/IP can deal with any ARP requests by itself.
Everything we need we get from the network layer.
Regards
Marcel
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