Date:	Mon, 6 Jun 2011 15:31:24 +0000
From:	BONNEAU Guy <gbonneau@...anda.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: Multicast IP packet routed between 2 ports nic on the same host

Here are the requested info.

ip link :

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:00:5a:11:60:4e brd ff:ff:ff:ff:ff:ff
3: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:21:70:d8:b4:f7 brd ff:ff:ff:ff:ff:ff
4: eth2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether 00:24:2b:66:73:a5 brd ff:ff:ff:ff:ff:ff

ip addr

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:00:5a:11:60:4e brd ff:ff:ff:ff:ff:ff
    inet 172.30.8.31/24 brd 172.30.8.255 scope global eth1
    inet6 fe80::200:5aff:fe11:604e/64 scope link 
       valid_lft forever preferred_lft forever
3: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 00:21:70:d8:b4:f7 brd ff:ff:ff:ff:ff:ff
    inet 10.0.9.164/16 brd 10.0.255.255 scope global eth0
    inet6 fe80::221:70ff:fed8:b4f7/64 scope link 
       valid_lft forever preferred_lft forever
4: eth2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether 00:24:2b:66:73:a5 brd ff:ff:ff:ff:ff:ff

ip ro

172.30.8.0/24 dev eth1  proto kernel  scope link  src 172.30.8.31  metric 1 
10.0.0.0/16 dev eth0  proto kernel  scope link  src 10.0.9.164  metric 1 
169.254.0.0/16 dev eth0  scope link  metric 1000 
default via 10.0.0.62 dev eth0  proto static 


> I am trying to receive multicast data packets from a multicast router
> to my Linux Ubuntu Desktop Workstation using kernel 2.6.35. The Linux
> Desktop has an Intel 82576 dual NIC adapter. Each NIC is configured to
> receive IP data from 2 different subnet. One is from 172.30.8.xx and
> another one from 10.0.xx.xx. Multicast IP data can only be received
> from 172.30.8.xx since there is no multicast source on subnet
> 10.0.xx.xx and IT that administrates the subnet 10.0.xx.xx disabled
> multicast capability of the switches and routers sitting on that
> subnet. The subnet 172.30.8.xx has multicast source broadcasting on
> multicast group 239.255.200.200:8000.
>

Hi

Not clear if eth0 and eth1 are on both networks ?

Please send us

ip link
ip addr
ip ro

Thanks

> I am using the application mreceived (version 2.2) from :
> http://www.cs.virginia.edu/~mngroup/software/ to test the network
> multicast set-up and capability of my Ubuntu Desktop Workstation.
>
> I open a first console and I use mreceive to join multicast group
> 239.255.200.200:8000 to receive multicast data from subnet 10.0.xx.xx
> using the console command : ./mreceive -g 239.255.200.200 -p 8000 -i
> 10.0.9.164 to the eth0 adapter of my workstation. The application is
> idle and no multicast data is received. This is the expected
> behaviour.
>
> I open a second console and I use mreceive to join the same multicast
> group 239.255.200.200:8000 to receive multicast data from subnet
> 172.30.8.xx using the console command : ./mreceive -g 239.255.200.200
> -p 8000 -i 172.30.8.31 to the eth1 adapter of my workstation. The
> application starts to receive multicast data and advertises the data
> received. This is also the expected behaviour.
>
> Now this is where the problem begins. As soon as the multicast data
> begin to be received on the eth1 adapter the first console begins to
> advertise multicast data received on eth0 adapter. I am well aware
> that the Linux kernel implements a multicast level 2 routing
> capability. Thus at first glance this seems to be the expected
> behaviour. However... I have forwarding disabled as well as
> mc_forwarding disabled and rp_filter is enabled for both adapters.
> Thus I don't expect the kernel to forward the multicast data from eth1
> to eth0.
>
> I have recompiled the kernel with IP Multicast Routing disabled and
> got the same behavior. I also tried kernel 2.6.38 and had the same
> issue.
>
> At this point I am inclined to think that the kernel multicast routing
> might have an issue? I might have missing a network configuration
> setting but at this point I am baffled.  I checked the kernel bugbase
> with the multicast tagging and couldn't find a filled bug regarding
> this matter. The only remaining options for me are to fill a bug and
> trace the kernel code (ipmr.c) to understand what going on. Can
> someone shade light on this? Is this an expected behavior or an issue?
>
> Thanks
> GB
>


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