n-Arno / scw-wau

Watch and Update private nics from metadata and config file.

scw-wau (Watch and Update)

This small utility read Scaleway Instance metadata and update PN nics according to a configuration file.

It is intended to be run in the background and will watch for change in private nics metadata and update nics ip and routes accordingly.

Building

You can use gnu/make or just run go build.

If you are using gnu/make, you can run make install to build, install binary in /usr/local/bin and install service.

In any case, once build, the service can be installed/started/stopped using daemon commands:

# scw-wau help

Usage: scw-wau install | remove | start | stop | status | help

Once installed, the service can also be managed through standard systemd commands:

# systemctl status scw-wau

● scw-wau.service - Scaleway PN Watch and Update
     Loaded: loaded (/etc/systemd/system/scw-wau.service; enabled; vendor preset: enabled)
     Active: active (running) since Sun 2022-12-18 12:59:37 UTC; 5s ago
    Process: 25250 ExecStartPre=/bin/rm -f /var/run/scw-wau.pid (code=exited, status=0/SUCCESS)
   Main PID: 25251 (scw-wau)
      Tasks: 8 (limit: 1112)
     Memory: 1.3M
        CPU: 15ms
     CGroup: /system.slice/scw-wau.service
             └─25251 /usr/local/bin/scw-wau

Config

An example config file is provided:

pns:
  - id: 47d39527-08ea-4956-b581-ed7a2e73b69e
    ip: 192.168.0.1/24
  - id: 513a6cf1-8f47-403b-9aaa-6815c5654fb6
    ip: 192.168.1.1/24
    ex: "echo done > /tmp/updated-pn"
routes:
  - 192.168.3.0/24 via 192.168.1.2

In pns, multiple nic can be configured using the following values:

• id: Mandatory private network id
• ip: Mandatory ip address for the corresponding nic, in CIDR format
• ex: Optionnal command to execute if nic is configured, for example to start an associated service

Some routes can be configured using the routes list. Each route must be in the format <destination network> via <gateway ip>.

The default route can be configured using default as destination network, but be aware it delete the existing default route. Use at your own risk.

Running

scw-wau can be run standalone, as a background process or as a service (once installed).

Here is the sample log output of the command:

2022/12/18 13:09:46 Reading config file pn.yaml.example...
2022/12/18 13:09:46 Done!
2022/12/18 13:09:46 Starting pooling every 10 seconds
2022/12/18 13:09:46 New private nics state: [{47d39527-08ea-4956-b581-ed7a2e73b69e 02:00:00:11:c4:68} {513a6cf1-8f47-403b-9aaa-6815c5654fb6 02:00:00:11:c3:dc}]
2022/12/18 13:09:46 Found interface ens6 with mac address 02:00:00:11:c3:dc
2022/12/18 13:09:46 Associated config exists for ens6 (192.168.1.1/24)
2022/12/18 13:09:46 Found interface ens5 with mac address 02:00:00:11:c4:68
2022/12/18 13:09:46 Associated config exists for ens5 (192.168.0.1/24)
2022/12/18 13:09:46 Added 192.168.1.1/24 to ens6
2022/12/18 13:09:46 Added 192.168.0.1/24 to ens5
2022/12/18 13:09:46 Run 'echo done > /tmp/updated-pn' with success
2022/12/18 13:09:46 Added route 192.168.3.0/24 via 192.168.1.2

Two flags can be passed to the main command:

# scw-wau --help

Usage of scw-wau:
  -c string
    	config filename (default "/etc/scw-wau/pn.yaml")
  -p int
    	pooling time (default 10)

Preparation

Scaleway instances already have some mecanism to help private network nics configuration.

To use scw-wau, it is preferable to deactivate these mecanism, here is an example on how on ubuntu instances:

rm -f /lib/systemd/system/scw-vpc-iface@.service
systemctl daemon-reload

cat<<EOF>/etc/cloud/cloud.cfg.d/99-custom-networking.cfg
{config: disabled}
EOF

cat<<EOF>/etc/netplan/custom-config.yaml
network:
  version: 2
  ethernets:
    ens2:
      dhcp4: true
EOF

rm -f /etc/netplan/50-cloud-init.yaml
netplan generate
netplan apply