Access the Internet over Thread from Android Things

[MSohm]

I'm trying to connect to the Internet from Android Things connected to an NCP through the OpenThread Border Router.

1 Raspberry PI running RaspPi_OT_Border_Router_Demo_v2.0.0-1.alpha. This device is also connected to IPv4 ethernet connection to the Internet.
2 Raspberry PIs running Android Things
Each device is connected to a Nordic nRF52840-PDK over USB.

I am able to run the CLI example with an nRF52840 connected to my computer and ping 64:ff9b::0808:0808, so Internet connectivity over thread appears to be working.

Using the Android Things LowPan sample and Thread network created by the Border Router, the two things devices are able to see and connect to one another**.

I then modified the LowPan sample to connect to servers outside the Thread network (making a socket connection to a public web server), but am not able to connect to anything.

If I try to connect to a public external IPv4 address (converted to IPv6 with the 64:ff9b:: prefix) I get:

android.system.ErrnoException: connect failed: ENETUNREACH (Network is unreachable)

If I try to connect to a public host name I get:

android.system.GaiException: android_getaddrinfo failed: EAI_NODATA (No address associated with hostname)

Has anyone gotten Android Things working in this way?  Is there any special configuration required on the Border Router?

** I had to change the name of the Thread Network that is configured by default, otherwise the Android Things devices threw an exception about invalid characters.

[Jørgen Holmefjord]

Hi,

I got some more information from our developers and some proposition to help resolving this issue:

It is important to find out at what point frames to public IP address get lost. We can observe the 802.15.4 traffic using this sniffer software: https://github.com/NordicPlayground/nRF-802.15.4-sniffer

Also we need to observe traffic at the border router and Android Things network interfaces using tcpdump. Interfaces of interest: wpanX, nat64, wlanX or ethX.

This is the proposed setup:

I am not familiar with Android Things but I suppose the tcpdump should be launched like this:

adb shell tcpdump -i wpanX &

Then we should ping a server and see the traffic on tcpdump and 802.15.4 sniffer.

If there is no traffic visible then the first thing to check would be the routing table:

adb shell route -6

This should help us pinpoint the location of the issue and move further.

Best regards,
Jørgen

[Jørgen Holmefjord]

Perhaps it is worth changing the well-known nat64 prefix from 64:ff9b::/96 to some other value on the border router and change route settings on the Android Things device accordingly.

Is any traffic visible on 802.15.4 sniffer?

It could also be used to verify if AT devices and border router are connecting properly.

[Jørgen Holmefjord]

Can you upload the sniffer traces?

[MSohm]

Here are the packet captures:  https://drive.google.com/file/d/1SoW1s1qKjwlUE5mbkRILGJWxVmkCela1/view?usp=sharing

Local communication - Is from the Android Things device to a server running on the border router.

Internet communication - Is from the Android Things device to a public Internet server.

[Jørgen Holmefjord]

The traces seems to be encrypted. Can you provide decryption key, or provide new traces with key exchange included?

[MSohm]

The network key is 4554ab2c58e2218ef5e4fec886100af7

[Jørgen Holmefjord]

It would appear that the packets are not correctly routed by the Android things device and do not leave the device over the mesh network. The network itself however appears to be establishing itself correctly in both cases.

Did you try changing the well known NAT64 prefix in border router settings from 64:ff9b::/96 to something else and setting the routing table in Android things device accordingly?

The NAT64 settings should be in /etc/tayga.conf in the border router. The packets with nat64 prefix should be routed to wpanX interface on the Android things device.

[MSohm]

I tried changing the NAT64 prefix to 2001:db8:1:ffff::/96 and ran the commands below on the Android Things device, but behaviour didn't change.

adb shell su 0 ip route add table wpan1 64:ff9b::/96 dev wpan1 proto kernel scope link src fd45:5412:9874:0:667b:4209:4a08:d4b0 metric 1
adb shell su 0 ip route add table wpan1 2001:db8:1:ffff::/96 dev wpan1 proto kernel scope link src fd45:5412:9874:0:667b:4209:4a08:d4b0 metric 1

[Jørgen Holmefjord]

Can you try to add a route through the border router:

adb shell ip -6 route add default via <border-router-mesh-local-IP> dev wpan1

Note the 'via' keyword, and that the address should be that of the border router, not the website.

[MSohm]

I still get connect failed: ENETUNREACH (Network is unreachable) after running that command.

At this point, based on Google's comments that they are focusing Android Things on smart screens and smart speakers only, this project will adjust to use something other than Android Things.  Thanks for all the help so far, but we don't need to continue this further.