Public IPv6 (6LoWPAN/RPL) network with A8-M3 nodes

Difficulty: Medium Duration: 45 minutes

Prerequisites: Configure SSH Access , RIOT basics

Description: The goal of this tutorial is to discover the basics of RIOT GNRC stack & tools for IoT-LAB IPv6. You will reserve 2 A8 nodes on the Saclay site, build 2 firmwares and flash them on the A8-M3 nodes, and create a simple IPv6 network in IoT-LAB. Finally, you’ll access nodes using UDP over IPv6 from the SSH frontend (or any Host with a global IPv6 address), using RIOT network automatic configuration tools.

Connect to Saclay SSH frontend:

my_computer$ ssh <login>@saclay.iot-lab.info

Start an experiment called riot_ipv6_a8 that contains 2 A8 nodes.
```
login@saclay:~$ iotlab-auth -u <login> 
login@saclay:~$ iotlab-experiment submit -n riot_a8 -d 60 -l 2,archi=a8:at86rf231+site=saclay
```
Remember the experiment identifier returned by the last command. It’ll be used in the commands shown below, <exp_id>. The requested experiment duration is 60 minutes.

Wait a moment until all nodes are up:

  login@saclay:~$ iotlab-ssh --verbose wait-for-boot

Wait a moment until the experiment is launched (state is Running) and get the nodes list. For the next of this tutorial we suppose that you obtained a8-1.saclay.iot-lab.info and a8-2.saclay.iot-lab.info nodes.
```
login@saclay:~$ iotlab-experiment get -i <exp_id> -p
login@saclay:~$ iotlab-experiment get -i <exp_id> -n
```
Get the code of the 2020.10 release of RIOT from GitHub:
```
login@saclay:~$ mkdir -p ~/A8/riot
login@saclay:~$ cd ~/A8/riot
login@saclay:~/A8/riot$ git clone https://github.com/RIOT-OS/RIOT.git -b 2020.10-branch
login@saclay:~/A8/riot$ cd RIOT
```
Note that you can also use the RIOT development code (e.g the master branch) at your own risk : this tutorial may not fully work.

Important note: to minimize radio interferences with other experiments you can build the firmwares below to make them use a different 802.15.4 channel (default is 26).
To do so, add DEFAULT_CHANNEL=<channel> option to the make commands.

Build the required firmware for the border router node. The node node-a8-1 will act as the border router in this experiment. The border firmware is built using the RIOT gnrc_border_router example

login@saclay:~/A8/riot/RIOT$ source /opt/riot.source
login@saclay:~/A8/riot/RIOT$ make ETHOS_BAUDRATE=500000 DEFAULT_CHANNEL=<channel> BOARD=iotlab-a8-m3 -C examples/gnrc_border_router clean all
login@saclay:~/A8/riot/RIOT$ cp examples/gnrc_border_router/bin/iotlab-a8-m3/gnrc_border_router.elf ~/A8/.

Build the required firmware for the other node. RIOT gnrc_networking example will be used for this purpose.

login@saclay:~/A8/riot/RIOT$ make DEFAULT_CHANNEL=<channel> BOARD=iotlab-a8-m3 -C examples/gnrc_networking clean all
login@saclay:~/A8/riot/RIOT$ cp examples/gnrc_networking/bin/iotlab-a8-m3/gnrc_networking.elf ~/A8/

Connect to the A8 of the M3 border router: node-a8-1.

login@saclay:~$ ssh root@node-a8-1

Then flash the BR firmware on the M3 and build the required RIOT configuration tools: uhcpd (Micro Host Configuration Protocol) and ethos (Ethernet Over Serial).

root@node-a8-1:~# iotlab_flash A8/gnrc_border_router.elf
root@node-a8-1:~# cd ~/A8/riot/RIOT/dist/tools/uhcpd 
root@node-a8-1:~/A8/riot/RIOT/dist/tools/uhcpd# make clean all
root@node-a8-1:~/A8/riot/RIOT/dist/tools/uhcpd# cd ../ethos
root@node-a8-1:~/A8/riot/RIOT/dist/tools/ethos# make clean all

On the border router, the network can finally be configured automatically using the following commands:

root@node-a8-1:~/A8/riot/RIOT/dist/tools/ethos# ./start_network.sh /dev/ttyA8_M3 tap0 2001:660:3207:401::/64 500000
net.ipv6.conf.tap0.forwarding = 1
net.ipv6.conf.tap0.accept_ra = 0
----> ethos: sending hello.
----> ethos: activating serial pass through.
----> ethos: hello reply received

Note that we propagate another subnetwork for the border router (M3 node) in our LLN, 2001:660:3207:401::/64. You can find informations about IPv6 subnetting for A8-M3 nodes here. You can also get this prefix directly on the A8 node:

root@node-a8-1:~# printenv
INET6_PREFIX_LEN=64
INET6_PREFIX=2001:0660:3207:401
INET6_ADDR=2001:0660:3207:0400::1/64

Now, in another terminal, log on the remaining A8 node, node-a8-2, and flash the gnrc_networking firmware on the M3:

my_computer$ ssh <login>@saclay.iot-lab.info
login@saclay:~$ ssh root@node-a8-2
root@node-a8-2:~# iotlab_flash A8/gnrc_networking.elf

Connect to the RIOT shell on the M3 using miniterm.py:

root@node-a8-2:~# miniterm.py -e /dev/ttyA8_M3 500000

From the RIOT shell, one can ping an Internet host (let’s try a Google DNS host):

> ping6 2001:4860:4860::8888
ping6 2001:4860:4860::8888
12 bytes from 2001:4860:4860::8888: id=83 seq=1 hop limit=50 time = 36.113 ms
12 bytes from 2001:4860:4860::8888: id=83 seq=2 hop limit=50 time = 34.839 ms
12 bytes from 2001:4860:4860::8888: id=83 seq=3 hop limit=50 time = 36.918 ms
--- 2001:4860:4860::8888 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2.06113456 s
rtt min/avg/max = 34.839/35.956/36.918 ms

Use RIOT shell ifconfig command to get the IP of the M3 node:

> ifconfig
Iface  7   HWaddr: 29:02  Channel: 26  Page: 0  NID: 0x23
        Long HWaddr: 36:32:48:33:46:df:a9:02 
        TX-Power: 0dBm  State: IDLE  max. Retrans.: 3  CSMA Retries: 4 
        AUTOACK  CSMA  MTU:1280  HL:64  6LO  RTR  RTR_ADV  IPHC  
        Source address length: 8
        Link type: wireless
        inet6 addr: ff02::1/128  scope: local [multicast]
        inet6 addr: fe80::3432:4833:46df:a902/64  scope: local
        inet6 addr: ff02::1:ffdf:a902/128  scope: local [multicast]
        inet6 addr: 2001:660:3207:401:3432:4833:46df:a902/64  scope: global
        inet6 addr: ff02::2/128  scope: local [multicast]

The global prefix has been successfully propagated, the IP on the M3 is 2001:660:3207:401:3432:4833:46df:a902. Verify that it answers to “ping” from the SSH frontend (and from any computer with a global IPv6):

login@saclay:~$ ping6 -c 3 2001:660:3207:401:3432:4833:46df:a902
PING 2001:660:3207:401:3432:4833:46df:a902(2001:660:3207:401:3432:4833:46df:a902) 56 data bytes
64 bytes from 2001:660:3207:401:3432:4833:46df:a902: icmp_seq=1 ttl=61 time=45.7 ms
64 bytes from 2001:660:3207:401:3432:4833:46df:a902: icmp_seq=2 ttl=61 time=46.5 ms
64 bytes from 2001:660:3207:401:3432:4833:46df:a902: icmp_seq=3 ttl=61 time=44.9 ms
   
--- 2001:660:3207:401:3432:4833:46df:a902 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 44.919/45.759/46.595/0.684 ms

Still on node-a8-2, let’s verify that UDP packets can be received from the site-host. Use udp command from gnrc_networking example to start an UDP server on the M3 node:

> udp server start 8888
udp server start 8888
Success: started UDP server on port 8888

Then from the site host, send a message by udp:

login@saclay:~$ echo "hello" > /dev/udp/2001:660:3207:401:3432:4833:46df:a902/8888

The packet has been received by the M3 node:

> PKTDUMP: data received:
~~ SNIP  0 - size:   5 byte, type: NETTYPE_UNDEF (0)
000000 68 65 6c 6c 6f
~~ SNIP  1 - size:   8 byte, type: NETTYPE_UDP (4)
   src-port: 49568  dst-port:  8888
   length: 13  cksum: 0x45fb6
~~ SNIP  2 - size:  40 byte, type: NETTYPE_IPV6 (2)
traffic class: 0x00 (ECN: 0x0, DSCP: 0x00)
flow label: 0x92520
length: 13  next header: 17  hop limit: 52
source address: 2a01:e35:2eba:eea0:21e:64ff:fefe:f394
destination address: 2001:660:3207:401:3432:4833:46df:a902
~~ SNIP  3 - size:  24 byte, type: NETTYPE_NETIF (-1)
if_pid: 7  rssi: 18  lqi: 255
src_l2addr: 36:32:48:33:46:d4:9a:22
dst_l2addr: 36:32:48:33:46:df:a9:02
~~ PKT    -  4 snips, total size:  77 byte

If everything works as described, the Border Router is correctly configured. Congratulations !