Multicast not working

bruzzel · 2012-03-04 12:03:19

Can't get multicast to work on my local network from a machine with kernel:
3.2.8-1-ARCH #1 SMP PREEMPT Mon Feb 27 21:51:46 CET 2012 x86_64 AMD Athlon(tm) 64 Processor 3400+ AuthenticAMD GNU/Linux

I manually added routes 239.0.0.0/8 and 224.0.0.0/4 to my routing table:
route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
default 192.168.1.1 0.0.0.0 UG 202 0 0 eth0
192.168.1.0 * 255.255.255.0 U 202 0 0 eth0
239.0.0.0 * 255.0.0.0 U 0 0 0 eth0

ip route show
default via 192.168.1.1 dev eth0 metric 202
192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.7 metric 202
multicast 224.0.0.0/4 dev eth0 scope link
239.0.0.0/8 dev eth0 scope link

I added this to my rc.conf (apparently not mentioned in the man page):
ROUTES=(!gateway multicast)
interface=eth0
address=
netmask=
broadcast=
gateway=""
multicast="-net 239.0.0.0 netmask 255.0.0.0 eth0"

(this doesn't modify the routing table by itself, I think it makes no sense here)

My ethernet device is a simple one:
00:12.0 Ethernet controller [0200]: VIA Technologies, Inc. VT6102 [Rhine-II] [1106:3065] (rev 78)
(from lspci)

ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 metric 1
inet 192.168.1.7 netmask 255.255.255.0 broadcast 192.168.1.255
inet6 fe80::215:f2ff:fe43:5479 prefixlen 64 scopeid 0x20<link>
ether 00:15:f2:43:54:79 txqueuelen 1000 (Ethernet)
RX packets 85228 bytes 118739653 (113.2 MiB)
RX errors 0 dropped 4 overruns 0 frame 0
TX packets 45558 bytes 3645314 (3.4 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 23 base 0xa000

But ping 224.0.0.1 gives no reply from my local machine as I thought it should:
ping 224.0.0.1
PING 224.0.0.1 (224.0.0.1) 56(84) bytes of data.

And while trying to multicast a DVB transport stream tcpdump shows only some sparse traffic on 192.168.0.x, but nothing on multicasting addresses, and the ethernet led is hardly blinking.

What am I overlooking??

pyther · 2012-03-04 15:46:03

First, get rid of all that multicast configuration stuff. You don't need any of it. Secondly, you won't be able to ping a multicast address. There won't be a machine, on the network, that will respond.

Once that is done, you need to give a bit more information on how and what you are trying to stream.

bruzzel · 2012-03-05 08:50:03

Don't need any of it? The Arch wiki page on multicasting needs some tidying then.

I'm trying to stream an mpeg/dvb transport stream (or part of it) from a dvb pci board. The receiver is OK, I can watch locally with Kaffeine and mplayer. I tried to stream both with dvblast http://www.videolan.org/projects/dvblast.html and mumudvb http://mumudvb.braice.net/mumudrupal/
They produce no error messages while streaming (but no multicast output either, at least not visible with tcpdump), so I was convinced the problem was with my networking setup.
BTW: my iptables is all open too.

pyther · 2012-03-05 13:06:08

What machine are you running tcpdump from? The run running dvblast?

When you are watching locally, you are watching the multicast stream, correct? Is the destination host a wired device (not wireless)? What is connecting the two devices?

Wikipedia wrote:

224.0.0.1 The All Hosts multicast group addresses all hosts on the same network segment.
Addresses in the range 224.0.0.0 to 224.0.0.255 are individually assigned by IANA and designated for multicasting on the local subnetwork only.

Basically you are using a reserved address, this might be causing other goofy issues to happen. What happens if you try an address such as 239.255.1.1

bruzzel · 2012-03-06 08:05:12

>What machine are you running tcpdump from? The run running dvblast?
Right.

>When you are watching locally, you are watching the multicast stream, correct?
No, I'm watching the DVB adaptor output: mplayer dvb://program1
I mentioned it just to illustrate the adaptor is OK.

>Is the destination host a wired device
No, wireless. The multicasting host is wired though, and there's a switch in between (Sagem).

>What happens if you try an address such as 239.255.1.1
Same thing: nothing on tcpdump.

I managed to get multicast output with mumudvb yesterday, but not with dvblast. And it is on the wired network, but invisible on the wireless part.

ploub · 2012-03-06 20:33:25

bruzzel wrote:

>Is the destination host a wired device
No, wireless. The multicasting host is wired though, and there's a switch in between (Sagem).
>What happens if you try an address such as 239.255.1.1
Same thing: nothing on tcpdump.
I managed to get multicast output with mumudvb yesterday, but not with dvblast. And it is on the wired network, but invisible on the wireless part.

I don't know anything about multicast but I did read this [by toofishes] while trying to get Xyne's pacserve to work with multicast on my wired and wireless network

...if your network segments are routed and not bridged, multicast traffic will likely not cross the barrier. 
A good example of this is your wireless/wired components of your home network...

Last edited by ploub (2012-03-06 20:39:59)

pyther · 2012-03-06 21:31:51

Typically multicast traffic does not go over wireless.It seems like VLC's streaming capabilities might be of some use to you. You can do an http stream (easiest) or an rtp stream to a specific host (advanced). Just open vlc, stream, select Capture Device and select the appropriate settings.

Arch Linux

#1 2012-03-04 12:03:19

Multicast not working

#2 2012-03-04 15:46:03

Re: Multicast not working

#3 2012-03-05 08:50:03

Re: Multicast not working

#4 2012-03-05 13:06:08

Re: Multicast not working

#5 2012-03-06 08:05:12

Re: Multicast not working

#6 2012-03-06 20:33:25

Re: Multicast not working

#7 2012-03-06 21:31:51

Re: Multicast not working

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