openvpn + zeroconf browser sending mdns query packets over e

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openvpn + zeroconf browser sending mdns query packets over e

Postby mrunal » Mon Jun 11, 2012 4:51 pm

Dear All,

On an android device, I am connecting to a remote network using openvpn for performing service discovery.

1. WORKING CASE: After the device is camped on 3g/4g and after connecting to remote network by openvpn, when the zeroconf browser is launched, I can see the mdns query packets being send through the tap0 interface resulting into rendering of services on the browser.

From the tcpdump captured on the device, I can see that the mdns query packets are send to tap0 interface.

tap0 ip: 192.168.11.200

Route table information:
Destination Gateway Genmask Flags Metric Ref Use Iface
76.26.112.234 10.179.240.1 255.255.255.255 UGH 0 0 0 pdpbr1
10.179.240.1 * 255.255.255.255 UH 0 0 0 pdpbr1
32.1.72.136 * 255.255.255.255 UH 0 0 0 pdpbr0
10.179.240.0 * 255.255.255.0 U 0 0 0 pdpbr1
192.168.11.0 * 255.255.255.0 U 0 0 0 tap0
default 192.168.11.1 0.0.0.0 UG 0 0 0 tap0

2. NOT WORKING CASE: However, after switching on the wifi and connecting it to remote network, when the zeroconf browser is launched, instead of sending the mdns query packets to tap0 interface; these packets are being send to eth0 interface due to which we cannot see the services.

From the tcpdump captured on the device, I can see that mdns query packets are send to eth0 interface.

tap0 ip: 192.168.11.200
eth0 ip: 192.168.43.230

route table information:
Destination Gateway Genmask Flags Metric Ref Use Iface
76.26.112.234 192.168.43.1 255.255.255.255 UGH 0 0 0 eth0
32.1.72.136 * 255.255.255.255 UH 0 0 0 pdpbr0
192.168.11.0 * 255.255.255.0 U 0 0 0 tap0
192.168.43.0 * 255.255.255.0 U 0 0 0 eth0
default 192.168.11.1 0.0.0.0 UG 0 0 0 tap0

In the above case, even though there is a default route for tap0, all the multicast packets are being routed through eth0. How is this possible?

Has anyone observed a similar problem and it would be really helpful if you can help us to discover services through zeroconf browser after the device is connected to remote network via openvpn through wifi.
mrunal
 
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Re: openvpn + zeroconf browser sending mdns query packets over e

Postby Melloware » Mon Jun 11, 2012 4:57 pm

I think it is a flaw in the design of the JmDNS library we use. I think it can be fixed they have some new code called JmmDNS which stands for "multihomed". I think it basically blasts for packets on all network interfaces it finds and it may just solve this problem.

Are you an Android developer by any chance?
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Re: openvpn + zeroconf browser sending mdns query packets over e

Postby mrunal » Tue Jun 12, 2012 1:59 am

Thank You very much for the reply.

When do you think will the new zeroconf browser be released that supports JmmDNS library on android market(free version :wink: )? Do you have any temporary solution to make this work?

I was thinking of using some iptables command to mark the mdns query packets and forward it to the required interface (tap0) instead of (eth0).

Yes, I am an android developer/student trying to explore the service discovery and zeroconf paradigm. :D
mrunal
 
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Re: openvpn + zeroconf browser sending mdns query packets over e

Postby Melloware » Tue Jun 12, 2012 5:19 am

I just created this ticket for myself, I will see if I can get to it quickly and put a release out there.

https://www.assembla.com/spaces/mellowa ... ter-issues
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Re: openvpn + zeroconf browser sending mdns query packets over e

Postby Melloware » Tue Jun 12, 2012 9:57 am

Actually JmmDNS is too unstable and still beta so I don't trust it.

if you are interested in debugging it in the Android device I could work with you to send you the code?
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Re: openvpn + zeroconf browser sending mdns query packets over e

Postby mrunal » Tue Jun 12, 2012 11:47 am

I would really be interested in debugging this problem. Kindly let me know what I need to do for this.
mrunal
 
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Re: openvpn + zeroconf browser sending mdns query packets over e

Postby Melloware » Tue Jun 12, 2012 11:48 am

I sent you an email.
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