ouster_dhcp

ouster_dhcp

This package provides a wrapper around dnsmasq for allocating an IP address to the Ouster LiDAR. To run the dhcp server:

$ ros2 run ouster_dhcp dhcp-server
sudo /usr/sbin/dnsmasq -C /dev/null -kd -F192.168.0.254,192.168.0.254 -i enp0s31f6 --bind-dynamic
dnsmasq: started, version 2.79 cachesize 150
dnsmasq: compile time options: IPv6 GNU-getopt DBus i18n IDN DHCP DHCPv6 no-Lua TFTP conntrack ipset auth DNSSEC loop-detect inotify
dnsmasq-dhcp: DHCP, IP range 192.168.0.254 -- 192.168.0.254, lease time 1h
dnsmasq-dhcp: DHCP, sockets bound exclusively to interface enp0s31f6
dnsmasq: reading /etc/resolv.conf
dnsmasq: using nameserver 127.0.0.53#53
dnsmasq: read /etc/hosts - 7 addresses
dnsmasq-dhcp: DHCPDISCOVER(enp0s31f6) bc:0f:a7:00:07:92
dnsmasq-dhcp: DHCPOFFER(enp0s31f6) 192.168.0.254 bc:0f:a7:00:07:92
dnsmasq-dhcp: DHCPDISCOVER(enp0s31f6) bc:0f:a7:00:07:92
dnsmasq-dhcp: DHCPOFFER(enp0s31f6) 192.168.0.254 bc:0f:a7:00:07:92
dnsmasq-dhcp: DHCPREQUEST(enp0s31f6) 192.168.0.254 bc:0f:a7:00:07:92
dnsmasq-dhcp: DHCPACK(enp0s31f6) 192.168.0.254 bc:0f:a7:00:07:92 os1-991937000055

The command above is run using the default arguments and expected outputs are shown. The help message for the program showing its arguments looks like:

$ ros2 run ouster_dhcp dhcp-server --help
usage: dhcp-server [-h] [-i IFACE] [--min-ip MIN_IP] [--max-ip MAX_IP]

Runs a local dhcp server using dnsmasq

optional arguments:
  -h, --help            show this help message and exit
  -i IFACE, --iface IFACE
                        Listen on this network interface (default: enp0s31f6)
  --min-ip MIN_IP       Low end of the IP allocation range (default:
                        192.168.0.254)
  --max-ip MAX_IP       High end of the IP allocation range (default:
                        192.168.0.254)

Effort has been made to try to make sensible default arguments, somewhat biased to my primary development set-up. Others can always override these defaults by explicitly passing parameters to the script.

On my laptop (where I am doing most of my Ouster development), I have three interfaces: enp0s31f6, lo, wlp3s0 which are my hardwired, local loopback, and wireless interfaces respectively. In my dev setup, I plug the Ouster directly into my hardwired interface (enp0s31f6). If I probe the system to list those interfaces dynamically and lexographically sort them, the hardwired one will be the first element of that list. So, my heuristic for the default interface will be the first one in that sorted list (and there will always be at least one since we have the local loopback). I then take the IP that is bound to that interface and make the assumption it is a Class C IPv4 address (so a 24-bit subnet mask). I then look at that network and serve up the highest valid IP address on that network (I assume I do not have that address). This lets me serve up an IP to my Ouster in a way that almost makes it act like the Ouster has a static IP address and I can set the parameters on the ROS2 driver making this assumption.

So, for clarity, my typical setup is to bind the static IP address of 192.168.0.92 (I use this for legacy reasons going back roughly almost 2 decades) to my hardwired interface, which on my current laptop is enp0s31f6. I then serve up an IP address range over dhcp that consists of a single address, specfically 192.168.0.254. Since I wire the Ouster directly to my machine I know it is the only device looking for an address and it will always be the same. So, I can treat it as static. Of course, we always have the explicit command line options that can override these assumptions.

Tip for when using together with Network Manager

If you are using Network Manager to manage your network connections (it is convenient on a laptop -- I am using it), you should take care to ensure your wired connection is activated prior to starting the DHCP server. In my case, I have named my wired configuration that I use with the Ouster wired-0. So, to first bring it up:

$ nmcli connection up wired-0
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/5)

You can see that my IP is now bound to the interface:

$ ip addr show dev enp0s31f6
2: enp0s31f6: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000
    link/ether e8:6a:64:f4:3c:5b brd ff:ff:ff:ff:ff:ff
    inet 192.168.0.92/24 brd 192.168.0.255 scope global noprefixroute enp0s31f6
       valid_lft forever preferred_lft forever
    inet6 fe80::fe1f:f914:cc92:db5b/64 scope link tentative
       valid_lft forever preferred_lft forever

Now I can start the dhcp server without having the Ouster powered on and serve addresses correctly:

$ ros2 run ouster_dhcp dhcp-server
sudo /usr/sbin/dnsmasq -C /dev/null -kd -F192.168.0.254,192.168.0.254 -i enp0s31f6 --bind-dynamic
[sudo] password for tpanzarella:
dnsmasq: started, version 2.79 cachesize 150
dnsmasq: compile time options: IPv6 GNU-getopt DBus i18n IDN DHCP DHCPv6 no-Lua TFTP conntrack ipset auth DNSSEC loop-detect inotify
dnsmasq-dhcp: DHCP, IP range 192.168.0.254 -- 192.168.0.254, lease time 1h
dnsmasq-dhcp: DHCP, sockets bound exclusively to interface enp0s31f6
dnsmasq: reading /etc/resolv.conf
dnsmasq: using nameserver 127.0.0.53#53
dnsmasq: read /etc/hosts - 7 addresses

And once I power on the Ouster we see it gets the 192.168.0.254 address that we expect

dnsmasq-dhcp: DHCPDISCOVER(enp0s31f6) bc:0f:a7:00:07:92
dnsmasq-dhcp: DHCPOFFER(enp0s31f6) 192.168.0.254 bc:0f:a7:00:07:92
dnsmasq-dhcp: DHCPDISCOVER(enp0s31f6) bc:0f:a7:00:07:92
dnsmasq-dhcp: DHCPOFFER(enp0s31f6) 192.168.0.254 bc:0f:a7:00:07:92
dnsmasq-dhcp: DHCPREQUEST(enp0s31f6) 192.168.0.254 bc:0f:a7:00:07:92
dnsmasq-dhcp: DHCPACK(enp0s31f6) 192.168.0.254 bc:0f:a7:00:07:92 os1-991937000055