nrf5 SDK IoT cannot ping nrf52840 from router

RE: nrf5 SDK IoT cannot ping nrf52840 from router

Stian Røed Hafskjold — Thu, 18 Mar 2021 20:46:19 GMT

The solution for the 30 second disconnect is described in this post: https://devzone.nordicsemi.com/f/nordic-q-a/37179/ipv6_medium_ble-c---on_ble_evt-does-not-implement-ble_gap_evt_data_length_update_request-event-which-leads-to-ll-request-timeout-with-linux-6lowpan-module

RE: nrf5 SDK IoT cannot ping nrf52840 from router

Stian Røed Hafskjold — Sun, 19 Jul 2020 18:08:08 GMT

Thanks for reporting back on the error! Sorry for not answering you yet, but we have limited capacity due to summer vacations. What I can say about the 30 seconds timeout is that, if I recall correctly, there is a connection update from the RPi which is not handled in the SDK code. I think it requests extended MTU, DLE or similar, which is not responded to, which leads to a disconnect. If you have a BLE sniffer you can see which request this is.

RE: nrf5 SDK IoT cannot ping nrf52840 from router

Moritz — Wed, 01 Jul 2020 15:10:08 GMT

FYI:

I found the error. Apparently the ipv6 address calculation is different than explained here: https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.iotsdk.v0.9.0/iot_sdk_user_guides_ipv6_address_creation.html?cp=7_4_2_4

The ipv6 address which worked is 2001:db8::81:1dff:fe38:2271 (global) respectively fe80::81:1dff:fe38:2271 (local).

I somehow had to remove the '2' before '81:1dff:...' but I don't know why because the board uses a public BLE address and therefore should have a '2' at this position.

But I still have the problem with the automatic BLE disconnect after approx. 30s, even if I spam ping requests or establish a tcp connection. Does anybody have a solution for this?

RE: nrf5 SDK IoT cannot ping nrf52840 from router

Moritz — Wed, 24 Jun 2020 16:01:48 GMT

Hi Stian thanks for your response!

1. Thanks for mentioning the typo in the address. I removed it but unfortunately it didn't solve the problem.

2. I ran the two "cat" commands you mentioned and both times the result was 1, so the values were set correctly.

3. I am running the TCP server example from $(SDK_ROOT)/examples/iot/tcp/server

4. The log from a connected terminal is always the same an doesn't really help. It just confirms that the BLE connect was successful and that the ipv6 interface was initialized:

<info> app_timer: RTC: initialized.␍␍␊
<info> app: Application started.␍␍␊
<info> app: Physical layer in connectable mode.␍␍␊
<info> app: Physical layer: connected.␍␍␊
<info> app: IPv6 interface up.␍␍␊

5. Concerning the ping of the link local address I did another try, but this time ensuring that the radvd service is stopped before and I also ensured that no global address to the bt0 interface is added. The shell script I wrote for this is the following:

#!/bin/sh
# execute as superuser!!!

# stop a possibly running radvd service
service radvd stop
# Mount debugfs file system.
mount -t debugfs none /sys/kernel/debug
# Load 6LoWPAN module.
modprobe bluetooth_6lowpan
# Enable the bluetooth 6lowpan module.
echo 1 > /sys/kernel/debug/bluetooth/6lowpan_enable
# Look for available HCI devices.
hciconfig
# Reset HCI device - for example hci0 device.
hciconfig hci0 reset
sleep 2
# Read 00:AA:BB:XX:YY:ZZ address of the nRF5x device.
#timeout 3s hcitool lescan
# Connect to the device.
echo "Connecting to device 00:81:1D:38:22:71"
echo "connect 00:81:1D:38:22:71 1" > /sys/kernel/debug/bluetooth/6lowpan_control
sleep 20 #sleep long enough to refresh wireshark interfaces
# Check if you have established a connection.
ifconfig bt0
echo "discover the link local addresses of the board"
ping6 -I bt0 ff02::1 -c 5
sleep 2
# Try to ping the device using its link-local address, for example, on bt0 interface.
echo " "
ping6 -I bt0 fe80::281:1dff:fe38:2271 -c 5

The corresponding terminal output to this shell script is:

mount: none is already mounted or /sys/kernel/debug busy
hci0:	Type: Primary  Bus: UART
	BD Address: B8:27:EB:F5:2A:08  ACL MTU: 1021:8  SCO MTU: 64:1
	UP RUNNING 
	RX bytes:2825 acl:49 sco:0 events:140 errors:0
	TX bytes:5831 acl:53 sco:0 commands:104 errors:0

Connecting to device 00:81:1D:38:22:71
bt0: flags=4161<UP,RUNNING,MULTICAST>  mtu 1280
        inet6 fe80::b827:ebff:fef5:2a08  prefixlen 64  scopeid 0x20<link>
        unspec B8-27-EB-F5-2A-08-00-00-00-00-00-00-00-00-00-00  txqueuelen 1000  (UNSPEC)
        RX packets 1  bytes 28 (28.0 B)
        RX errors 0  dropped 2  overruns 0  frame 0
        TX packets 17  bytes 1361 (1.3 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

discover the link local addresses of the board
PING ff02::1(ff02::1) from fe80::b827:ebff:fef5:2a08%bt0 bt0: 56 data bytes
64 bytes from fe80::b827:ebff:fef5:2a08%bt0: icmp_seq=1 ttl=64 time=0.185 ms
64 bytes from fe80::b827:ebff:fef5:2a08%bt0: icmp_seq=2 ttl=64 time=0.198 ms
64 bytes from fe80::b827:ebff:fef5:2a08%bt0: icmp_seq=3 ttl=64 time=0.168 ms
64 bytes from fe80::b827:ebff:fef5:2a08%bt0: icmp_seq=4 ttl=64 time=0.103 ms
64 bytes from fe80::b827:ebff:fef5:2a08%bt0: icmp_seq=5 ttl=64 time=0.106 ms

--- ff02::1 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4194ms
rtt min/avg/max/mdev = 0.103/0.152/0.198/0.039 ms
 
PING fe80::281:1dff:fe38:2271(fe80::281:1dff:fe38:2271) from fe80::b827:ebff:fef5:2a08%bt0 bt0: 56 data bytes
From fe80::b827:ebff:fef5:2a08%bt0 icmp_seq=1 Destination unreachable: Address unreachable
From fe80::b827:ebff:fef5:2a08%bt0 icmp_seq=2 Destination unreachable: Address unreachable
From fe80::b827:ebff:fef5:2a08%bt0 icmp_seq=3 Destination unreachable: Address unreachable
From fe80::b827:ebff:fef5:2a08%bt0 icmp_seq=4 Destination unreachable: Address unreachable
From fe80::b827:ebff:fef5:2a08%bt0 icmp_seq=5 Destination unreachable: Address unreachable

--- fe80::281:1dff:fe38:2271 ping statistics ---
5 packets transmitted, 0 received, +5 errors, 100% packet loss, time 4148ms

Apparently, the RaspberryPi's bt0 interface is not able to discover the link local address of the BLE board and therefore also cannot ping it.

The data sniffed by whireshark on the bt0 interface was as follows:
devzone.nordicsemi.com/.../ble_5F00_ipv6_5F00_nrf_5F00_sdk_5F00_local.pcapng
It just shows the ping requests from the bt0 interface but no response from the nrf52840 dk.

The serial terminal log output was again similar as shown above in point 4.

6. I could show you similar results for my try with radvd enabled and a global bt0 address (to address your point here: I indeed added/add the global address every time I reconnect the BLE device), but I don't think that the problem lies in the configuration of radvd, ipv6 forwarding and global addresses, if I'm even not able to detect and ping the BLE device's link local address.

I hope this gives you more information for further debugging help. Thank you very much!!!

RE: nrf5 SDK IoT cannot ping nrf52840 from router

Stian Røed Hafskjold — Wed, 24 Jun 2020 12:32:26 GMT

Can you check if 6lowpan_enable and forwarding are actually set by running:

cat /proc/sys/net/ipv6/conf/all/forwarding
cat /sys/kernel/debug/bluetooth/6lowpan_enable

if you install wireshark you can sniff the bt0 interface and see the traffic that is going though the bt0 interface. If you post the log here I can try and see if there's something wrong.

Which example are you running from the SDK, and have you made any changes? If you connect a terminal to the DK what is the log telling you?

There is still a typing mistake in the ping command in your last post. The last two bytes should be 2271, not 22:71

The ping command where you ping the link local address is correct, but here you don't add the global address to the bt0 interface, or restart radvd. You need to add the global address to the bt0 interface every time you reconnect to the BLE device.

RE: nrf5 SDK IoT cannot ping nrf52840 from router

Moritz — Wed, 24 Jun 2020 09:23:11 GMT

EDIT: I made a small mistake with the ping of the global ipv6 address of the board

The address has to be 2001:db8::281:1dff:fe38:22:71

But with this address I get no ping response:

ping the BLE device using the global address
PING 2001:db8::281:1dff:fe38:22:71(2001:db8:0:281:1dff:fe38:22:71) 56 data bytes

--- 2001:db8::281:1dff:fe38:22:71 ping statistics ---
5 packets transmitted, 0 received, 100% packet loss, time 4198ms