NEWBIE QUESTION : Why does the installer not detect multicast on interfaces

[Pranav Vaidya]

Hello,

I am a newbie with jini and I have a problem installing jini on linux. I
have a laptop with Fedora core 9 on it. I tried installing jini on the
windows xp (sp2) 32 bit partition and the jini installation was successful
in that it went ahead and showed me that the both eth0 and wlan0 are
multicast enabled and jini will use them for service discovery. I have used
this to experiment with Jini on windows. However, I wanted to shift to
experimenting on linux too.

However, I have a problem installing the same on my linux partition. The
following are the machine details.

$> uname -a
Linux localhost.localdomain 2.6.27.12-78.2.8.fc9.i686 #1 SMP Mon Jan 19
20:14:35 EST 2009 i686 i686 i386 GNU/Linux

$> java -version
java version "1.6.0_11"
Java(TM) SE Runtime Environment (build 1.6.0_11-b03)
Java HotSpot(TM) Server VM (build 11.0-b16, mixed mode)

$> ifconfig
eth0      Link encap:Ethernet  HWaddr xx:xx:xx:xx:xx
         UP BROADCAST MULTICAST  MTU:1500  Metric:1
         RX packets:0 errors:0 dropped:0 overruns:0 frame:0
         TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:1000
         RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

lo        Link encap:Local Loopback
         inet addr:127.0.0.1  Mask:255.0.0.0
         inet6 addr: ::1/128 Scope:Host
         UP LOOPBACK RUNNING  MTU:16436  Metric:1
         RX packets:5710 errors:0 dropped:0 overruns:0 frame:0
         TX packets:5710 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:0
         RX bytes:285916 (279.2 KiB)  TX bytes:285916 (279.2 KiB)

wlan0     Link encap:Ethernet  HWaddr xx:xx:xx:xx:xx
         inet addr:xx:xx:xx:xx:xx  Bcast:xx.xx.xx.xx  Mask:xx.xx.xx.xx
         inet6 addr: xx:xx:xx:xx:xx Scope:Link
         UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
         RX packets:1982 errors:0 dropped:0 overruns:0 frame:0
         TX packets:812 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:1000
         RX bytes:712819 (696.1 KiB)  TX bytes:132136 (129.0 KiB)

wmaster0  Link encap:UNSPEC  HWaddr xx:xx:xx:xx:xx
         UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
         RX packets:0 errors:0 dropped:0 overruns:0 frame:0
         TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:1000
         RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

I have tried installing jini using jini2_1.bin as well as jini2_1.jar and
both of them at the end of the installation tell me the following.

These network interfaces were found on this system:
wlan0: MULTICAST DISABLED
lo: MULTICAST DISABLED
By default Jini multicast discovery will use all of the network interfaces
that are multicast enabled.
WARNING: none of the network interfaces appear to have multicast enabled.
Jini multicast lookup discovery may not function properly.

Here is my problem:
The kernel seems to be compiled for multicast support  (as can be seen from
ifconfig) for both  interfaces I might use namely eth0 when I am in the lab
and wlan0 when I am at home (at home I use a wireless router connected to
DSL modem).

As per http://www.linuxdevices.com/articles/AT3724430088.html
I have done the following
$route add -net 224.0.0.0 netmask 240.0.0.0 dev eth0
 $ifconfig lo multicast
 $ifconfig eth0 multicast

Also, I can see this information in when I list this in route -n. I have
also changed my IP tables to allow the IP multicast traffic. I am at my wits
end in that I am not sure if this is all that is needed and if yes why is
the installer giving me this error. As far as I understand from what I read
about Jini is that IP multicast is essential for both service discovery as
well as peer lookup. IMHO, this is very important.

I was wondering what the issue might be for the aforementioned error. Any
help regarding is deeply appreciated.

And yeah, the same situation applied for a desktop linux machine with the
same kernel and FC9 that I have in my lab while the windows desktop machine
in my lab works fine.

Pranav

[Brian Pontarelli]

You don't have to use multicast for anything if you don't like. You  
can unicast your entire Jini setup.

On the flip side, I used to run Jini on Fedora, Debian, Ubuntu and  
others with no issues. It sounds like you have a lot of custom network  
configuration going on if you can't get multicast to work. In all my  
experience, multicast was enabled by default on all Linux distros and  
if it wasn't, you could alsways change that configuration using the  
standard GUI interfaces.

My first guess would be that your IP tables are dropping these packets  
and need to be reconfigured. I'd also take a step back and setup a  
simple Java program that sends out a multicast packet and another  
simple java program that receives them. See if you can do it outside  
of Jini. This might reveal some bad Jini config.

Lastly, if you can't get multicast to work at all, I'd consider  
dropping all your IP tables, reseting your interfaces and starting  
fresh. Generally after major interface changes, you might need to  
reboot as well. The init.d scripts to restart your network aren't  
always 100% reliable.

-bp

On Feb 13, 2009, at 10:31 AM, Pranav Vaidya wrote:

> Hello,
>
> I am a newbie with jini and I have a problem installing jini on  
> linux. I
> have a laptop with Fedora core 9 on it. I tried installing jini on the
> windows xp (sp2) 32 bit partition and the jini installation was  
> successful
> in that it went ahead and showed me that the both eth0 and wlan0 are
> multicast enabled and jini will use them for service discovery. I  
> have used
> this to experiment with Jini on windows. However, I wanted to shift to
> experimenting on linux too.
>
> However, I have a problem installing the same on my linux partition.  
> The
> following are the machine details.
>
> $> uname -a
> Linux localhost.localdomain 2.6.27.12-78.2.8.fc9.i686 #1 SMP Mon Jan  
> 19
> 20:14:35 EST 2009 i686 i686 i386 GNU/Linux
>
> $> java -version
> java version "1.6.0_11"
> Java(TM) SE Runtime Environment (build 1.6.0_11-b03)
> Java HotSpot(TM) Server VM (build 11.0-b16, mixed mode)
>
> $> ifconfig
> eth0      Link encap:Ethernet  HWaddr xx:xx:xx:xx:xx
>         UP BROADCAST MULTICAST  MTU:1500  Metric:1
>         RX packets:0 errors:0 dropped:0 overruns:0 frame:0
>         TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
>         collisions:0 txqueuelen:1000
>         RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
>
> lo        Link encap:Local Loopback
>         inet addr:127.0.0.1  Mask:255.0.0.0
>         inet6 addr: ::1/128 Scope:Host
>         UP LOOPBACK RUNNING  MTU:16436  Metric:1
>         RX packets:5710 errors:0 dropped:0 overruns:0 frame:0
>         TX packets:5710 errors:0 dropped:0 overruns:0 carrier:0
>         collisions:0 txqueuelen:0
>         RX bytes:285916 (279.2 KiB)  TX bytes:285916 (279.2 KiB)
>
> wlan0     Link encap:Ethernet  HWaddr xx:xx:xx:xx:xx
>         inet addr:xx:xx:xx:xx:xx  Bcast:xx.xx.xx.xx  Mask:xx.xx.xx.xx
>         inet6 addr: xx:xx:xx:xx:xx Scope:Link
>         UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>         RX packets:1982 errors:0 dropped:0 overruns:0 frame:0
>         TX packets:812 errors:0 dropped:0 overruns:0 carrier:0
>         collisions:0 txqueuelen:1000
>         RX bytes:712819 (696.1 KiB)  TX bytes:132136 (129.0 KiB)
>
> wmaster0  Link encap:UNSPEC  HWaddr xx:xx:xx:xx:xx
>         UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>         RX packets:0 errors:0 dropped:0 overruns:0 frame:0
>         TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
>         collisions:0 txqueuelen:1000
>         RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
>
> I have tried installing jini using jini2_1.bin as well as  
> jini2_1.jar and
> both of them at the end of the installation tell me the following.
>
> These network interfaces were found on this system:
> wlan0: MULTICAST DISABLED
> lo: MULTICAST DISABLED
> By default Jini multicast discovery will use all of the network  
> interfaces
> that are multicast enabled.
> WARNING: none of the network interfaces appear to have multicast  
> enabled.
> Jini multicast lookup discovery may not function properly.
>
> Here is my problem:
> The kernel seems to be compiled for multicast support  (as can be  
> seen from
> ifconfig) for both  interfaces I might use namely eth0 when I am in  
> the lab
> and wlan0 when I am at home (at home I use a wireless router  
> connected to
> DSL modem).
>
> As per http://www.linuxdevices.com/articles/AT3724430088.html
> I have done the following
> $route add -net 224.0.0.0 netmask 240.0.0.0 dev eth0
> $ifconfig lo multicast
> $ifconfig eth0 multicast
>
> Also, I can see this information in when I list this in route -n. I  
> have
> also changed my IP tables to allow the IP multicast traffic. I am at  
> my wits
> end in that I am not sure if this is all that is needed and if yes  
> why is
> the installer giving me this error. As far as I understand from what  
> I read
> about Jini is that IP multicast is essential for both service  
> discovery as
> well as peer lookup. IMHO, this is very important.
>
> I was wondering what the issue might be for the aforementioned  
> error. Any
> help regarding is deeply appreciated.
>
> And yeah, the same situation applied for a desktop linux machine  
> with the
> same kernel and FC9 that I have in my lab while the windows desktop  
> machine
> in my lab works fine.
>
> Pranav
> --
> View this message in context: http://www.nabble.com/NEWBIE-QUESTION-%3A-Why-does-the-installer-not-detect-multicast-on-interfaces-tp22001045p22001045.html
> Sent from the Sun - Jini-Users mailing list archive at Nabble.com.
>
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[Brian Pontarelli]

On Feb 13, 2009, at 5:47 PM, Pranav Vaidya wrote:

> Hello Brian,
>
> Thank you for helping me out as it was your email that led to debug  
> what might have been happening.
> I figured out what was happening atleast with eth0 and I am  
> perfectly fine with that. I will only go ahead and fiddle with wlan0  
> afterwards. Please ignore my previous "BS" as the issue had nothing  
> to do SELinux since I tested this with both the SELinux as well as  
> the firewall on.
>
> It seems to me that in case of a multihomed system (I know a new  
> term now !!), only the latest added route add -net 224.0.0.0 netmask  
> 240.0.0.0 dev takes effect (still dont know why ?). So in my effort  
> to get both lo as well as eth0 working, I was first adding the route  
> command for eth0 and then for lo hence lo was working and eth0 was  
> not.

You are still definitely doing more with your network than most out-of-
the-box users of Linux will. You shouldn't really need to setup routes  
at all and Linux should be able to correctly handle multicast traffic,  
even with a multihome setup. There should definitely be an order for  
the interfaces that are up and Jini should grab the first one unless  
otherwise told to use something else.

I used to do a presentation for the No Fluff Just Stuff tour that  
covered the Jini basics and had a quick setup for anyone that came to  
participate in a little Jini network. Worked great with Linux users,  
OS X, Windows, etc. We never needed any special tweaks. I dusted that  
sucker off when you posted your question, just to poke around again,  
and it all works fine without any tweaks.

I guess my question would be, what started you down the custom network  
configuration route in the first place and why didn't the default  
Linux configuration suit your needs?

-bp

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