[linux-dvb] DVB-H and dvbnet / MAC-broadcast address

Nico Sabbi nsabbi at email.it
Fri Mar 30 14:38:16 CEST 2007

Dietmar Zlabinger wrote:

> Hi,
> I am looking for help on receiving DVB-H.
> I get to the point where the encapsulated IP is attached to a network 
> interface (as dvb0_0 using dvbnet -p <portnr>). At this stage I am 
> able to dump the UDP-packets received using tcpdump. But I am not able 
> to get that IP-multicast into VLC.
> I believe the problem is related to the fact that normally 
> IP-multicast uses the Ethernet broadcast address (ff:ff...) while in 
> dvb-h the destination mac is (partly) replaced by the dvb-h time 
> slicing information . Therefore the traffic is only received by the 
> network interface when it is in promiscuous mode (when using tcpdump), 
> but not when a normal program (like vlc) is trying to get multicast 
> frames out of it.
> My idea then was to modify dvbnet so that it replaces the "broken" 
> ethernet destination (is contains timeslicing-infos) by "ff:ff" so 
> that it goes through the network interface. But the actual code of 
> dvbnet does actually not handle the received data, the only thing that 
> program does is some ioctl(fd_net).
> Any idea who I could get the ethernet-multicast out even when the 
> destination mac is wrong?
> Any idea how I could modify (the kernel) so that I could overwrite the 
> faulty mac?
> I could not find any description on how to receive dvb-h on the web. 
> The are some mailing on how to find SDP files, but that was not such a 
> big thing (dvbsnoop  -b <pid> ..).
> Thanks for help,
> Dietmar

premitting that I have very little confidence with networking in general...
if you run
$ ifconfig dvb0_0 ip/mask promisc up
$ route add -net dev dvb0_0
you shouldn't need to tamper with the MAC addresses.
You can also use smcrouted to re-route the tuple src_ip->dest_ip from 
dvb0_0 to eth0
(although I find it annoying having to know the source ip).
I ad dvb-h working in both manners.
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