Netns

Netns (network namespaces) are another instance of the network stack with its own network devices (links), ip setup and firewall rules. Besides of using netns for building containers they can be used to get a stricter isolation than using VRFs.

Prerequisites

The packages and patches described in this article are available in Alpine edge and ≥3.19.

NETNS management

iproute2

Netns can be ad-hoc managed using the ip netns commands.

ip netns
ip netns add tenant1
ip netns del tenant1
ip netns exec tenant1 ip -br link

ifstate

IfState, a declarative network configuration tool, is full netns aware since IfState 1.9.0. The following config example creates a wireguard tunnel and a vlan sub-interface. The wireguard link wg0 and the vlan sub-interface are moved into the vpn netns.

# root netns
interfaces:
  - name: eth0
    addresses:
    - 198.51.100.2/31
    link:
      state: up
      kind: physical
routing:
  routes:
    - to: 0.0.0.0/0
      via: 198.51.100.1
  rules: []

namespaces:
  # "vpn" netns
  vpn:
    interfaces:
    - name: eth0.42
      addresses:
      - 192.0.2.1/25
      link:
        state: up
        kind: vlan
        vlan_id: 42
        link: eth0
        # link to eth0 in root netns
        link_netns: null
    - name: wg0
      addresses:
      - 192.0.2.254/30
      link:
        state: up
        kind: wireguard
        # bind wireguard to the root netns
        bind_netns: null
      wireguard:
        private_key: !include /etc/wireguard/secret.key
        peers:
        - public_key: 3Eimby+9YtJwtx+peCsz6RiubRqAp+cATHNiGWsUsEU=
          endpoint: 203.0.113.42
          persistent_keepalive_interval: 30
          allowedips:
          - 0.0.0.0/0
    routing:
      routes: []
        - to: 0.0.0.0/0
          dev: wg0
      rules: []

NETNS-based Service Isolation

Services can be run isolated in a NETNS (and VRF inside the NETNS) when running at least OpenRC 0.49.0-r1. You can set the $netns variable for the service in /etc/conf.d in most cases.

The netns must already be created before a service can be started inside of it!

NETNS-compatible initd scripts

Not all initd scripts might be netns compatible. Some network stack related packages have been patched to be netns aware:

• ipset
• iptables
• nftables