Add example for bridge/tap network setup using systemd-networkd

6 files changed, 162 insertions, 0 deletions

diff --git a/etc/private/systemd-networkd/10-br0.netdev b/etc/private/systemd-networkd/10-br0.netdev
new file mode 100644
index 0000000..6431ba8
--- /dev/null
+++ b/etc/private/systemd-networkd/10-br0.netdev
@@ -0,0 +1,8 @@
+# Create a bridge network device.
+#
+# Use ethernet interface's MAC address as bridge MAC.
+
+[NetDev]
+Name=br0
+Kind=bridge
+MACAddress=02:11:11:11:11:11
diff --git a/etc/private/systemd-networkd/10-tap0.netdev b/etc/private/systemd-networkd/10-tap0.netdev
new file mode 100644
index 0000000..3989bd8
--- /dev/null
+++ b/etc/private/systemd-networkd/10-tap0.netdev
@@ -0,0 +1,12 @@
+# Create a tap network device.
+#
+# Set user/group to the user/group that will be using the tap
+# (e.g., the user that will run the VM that will use this tap).
+
+[NetDev]
+Name=tap0
+Kind=tap
+
+[Tap]
+#User=
+#Group=
diff --git a/etc/private/systemd-networkd/20-br0-eth0.network b/etc/private/systemd-networkd/20-br0-eth0.network
new file mode 100644
index 0000000..c57736f
--- /dev/null
+++ b/etc/private/systemd-networkd/20-br0-eth0.network
@@ -0,0 +1,12 @@
+# Add the ethernet interface to the bridge.
+#
+# Change eth0 to your ethernet interface name.
+
+[Match]
+Name=eth0
+
+[Network]
+Bridge=br0
+
+[Link]
+RequiredForOnline=no
diff --git a/etc/private/systemd-networkd/20-br0-tap0.network b/etc/private/systemd-networkd/20-br0-tap0.network
new file mode 100644
index 0000000..1c2c746
--- /dev/null
+++ b/etc/private/systemd-networkd/20-br0-tap0.network
@@ -0,0 +1,16 @@
+# Add the tap interface to the bridge.
+#
+# Note: do not assign MAC address to the tap interface, it's not the same
+# thing as the interface inside the VM (which is what we want to assign the
+# MAC address to).
+#
+
+[Match]
+Name=tap0
+
+[Network]
+Bridge=br0
+#ConfigureWithoutCarrier=yes
+
+[Link]
+RequiredForOnline=no
diff --git a/etc/private/systemd-networkd/30-br0-dhcp.network b/etc/private/systemd-networkd/30-br0-dhcp.network
new file mode 100644
index 0000000..864fe3d
--- /dev/null
+++ b/etc/private/systemd-networkd/30-br0-dhcp.network
@@ -0,0 +1,14 @@
+# Configure the bridge with IPv4 DHCP.
+
+[Match]
+Name=br0
+
+[Network]
+DHCP=ipv4
+IPForward=yes
+
+[DHCPv4]
+#UseHostname=yes
+
+[Link]
+RequiredForOnline=yes
diff --git a/etc/private/systemd-networkd/README b/etc/private/systemd-networkd/README
new file mode 100644
index 0000000..2db3904
--- /dev/null
+++ b/etc/private/systemd-networkd/README
@@ -0,0 +1,100 @@
+This directory contains sample configuration files for setting up a bridge
+(br0) and a permanent tap interface (tap0) using systemd's networkd network
+manager. The tap interface can be used, for example, to run a virtual machine
+that appears as a real machine on the host's Ethernet network.
+
+Assumptions:
+
+ - The host's Ethernet interface is eth0.
+ - The host uses IPv4 DHCP for network configuration.
+
+Note: only perform the following steps over a physical login to the host since
+the configuration involves bringing the host's networking down.
+
+
+1. Switch to systemd-networkd for network configuration.
+
+Overall, the goal of this step is to disable the currently used network
+manager and enable systemd-networkd. First check if systemd-networkd is
+already used:
+
+# systemctl status systemd-networkd
+
+If it's enabled and running, skip to step 2. Otherwise, identify the currently
+used network manager. The possible options depend on the distribution used so
+consult the relevant documentation for details. One common option is the GNOME
+network manager:
+
+# systemctl status NetworkManager
+
+If it's enabled and running, stop and disable:
+
+# systemctl stop NetworkManager
+# systemctl disable NetworkManager
+
+For Debian-based distributions a common approach is to define the network
+configuration in the /etc/network/interfaces file. To disable this method,
+perform the following steps:
+
+# systemctl stop networking
+# mv /etc/network/interfaces /etc/network/interfaces.disabled
+
+Once the current network manager is disabled, proceed to step 2.
+
+
+2. Configure bridged networking using systemd-networkd.
+
+Copy configuration files found in this directory to /etc/systemd/network/ (see
+the comment at the beginning of each file for its purpose):
+
+# cp *.netdev *.network /etc/systemd/network/
+
+Note: if you are already using systemd-networkd, then you may already have
+some configuration in /etc/systemd/network/. If the existing configuration
+conflicts with this setup (for example, you already have a configuration
+for eth0), then you will need to remove the relevant files.
+
+Then adjust the following to match your setup:
+
+  - Ethernet interface name if not eth0: 20-br0-eth0.network (both name and
+    content)
+
+  - Bridge MAC address: 10-br0.netdev
+
+    Use your Ethernet interface's address as your bridge address, which
+    you can obtain with:
+
+    # ip link show eth0
+
+  - Tap user/group: 10-tap0.netdev
+
+    For example, set to the user/group that will run the VM that will use this
+    tap interface.
+
+
+3. Test and enable networking using systemd-networkd.
+
+Once the configuration is complete, start/restart systemd-networkd and verify
+networking is configured correctly.
+
+# systemctl restart systemd-networkd
+# systemctl status systemd-networkd
+# ip addr show br0
+# ip addr show tap0
+
+Specifically, verify that:
+
+  - The br0 MAC address is correct.
+
+  - The br0 interface is assigned (via DHCP) an IP address and, if a fixed
+    IP is used, it's what's expected.
+
+  - Try to ping example.org to confirm the overall network (routing, DNS)
+    is functional.
+
+If everything looks good, enable systemd-networkd:
+
+# systemctl enable systemd-networkd
+
+You may also want to reboot the host and performs the above verifications
+one more time.