1.3. Networking

barebox has IPv4 networking support. Several protocols such as DHCP, NFS and TFTP are supported.

1.3.1. Network configuration

1.3.1.1. Lowlevel network device configuration

Network devices are configured with a set of device specific variables:

name	type
<devname>.mode	enum	“dhcp”: DHCP is used to get IP address and netmask “static”: Static IP setup described by variables below “disabled”: Interface unused
<devname>.ipaddr	ipv4 address	The IP address when using static configuration
<devname>.netmask	ipv4 address	The netmask when using static configuration
<devname>.gateway	ipv4 address	Alias for global.net.gateway. For compatibility, do not use.
<devname>.serverip	ipv4 address	Alias for global.net.server. For compatibility, do not use.
<devname>.ethaddr	MAC address	The MAC address of this device

Additionally there are some more variables that are not specific to a device:

name	type
global.net.gateway	ipv4 host	The network gateway used when a host is not in any directly visible subnet. May be set automatically by DHCP.
global.net.server	hostname or ipv4 address	The default server used by the defaultenv boot scripts for NFS and TFTP; see Network boot. If unspecified, may be set by DHCP.
global.net.nameserver	ipv4 address	The DNS server used for resolving host names. May be set by DHCP.
global.net.ifup_force_detect	boolean	Set to true if your network device is not detected automatically during start (i.e. for USB network adapters).

The first step for networking is configuring the network device. The network device is usually eth0. The current configuration can be viewed with the devinfo command:

barebox:/ devinfo eth0
Parameters:
  ethaddr: 00:1c:49:01:03:4b
  ipaddr: 192.168.23.197
  netmask: 255.255.0.0
  [...]

The configuration can be changed on the command line with:

eth0.ipaddr=172.0.0.10

The dhcp command will change the settings based on the answer from the DHCP server.

To make the network device settings persistent across reboots there is a nonvolatile variable (nvvar) for each of the variables above. The network device specific variables are:

nv.dev.<devname>.mode
nv.dev.<devname>.ipaddr
nv.dev.<devname>.netmask
nv.dev.<devname>.ethaddr

The others are:

nv.net.gateway
nv.net.server
nv.net.nameserver

A typical simple network setting is to use DHCP. Provided the network interface is eth0 then this would configure the network device for DHCP:

nv dev.eth0.mode=dhcp

(In fact DHCP is the default, so the above is not necessary)

A static setup would look like:

nv dev.eth0.mode=static
nv dev.eth0.ipaddr=192.168.0.17
nv dev.eth0.netmask=255.255.0.0
nv net.server=192.168.0.1

The settings can be activated with the ifup command:

ifup eth0

or:

ifup -a

‘ifup -a’ will activate all ethernet interfaces, also the ones on USB.

1.3.2. Network filesystems

barebox supports NFS and TFTP both with commands (nfs and tftp) and as filesystem implementations; see NFS Support and TFTP filesystem for more information. After the network device has been brought up, a network filesystem can be mounted with:

mount -t tftp 192.168.2.1 /mnt

or

mount -t nfs 192.168.2.1:/export none /mnt

1.3.2.1. Automounts

For user convenience, the default automount init script runs the automount command to create automounts for both TFTP and NFS. On first access, an Ethernet interface will be brought up and file operations will be forwarded to a host specified by global variables:

• /mnt/tftp: will use $global.net.server as TFTP server

• /mnt/nfs: will use $global.net.server as NFS server and /home/${global.user}/nfsroot/${global.hostname} as nfsroot. By default, a RPC lookup will be conducted to determine mount and NFS ports, but these can be overridden together using a user-specified by means of global.nfs.port. The latter is equivalent to specifying -o port=$global.nfs.port,mountport=$global.nfs.port as argument to the mount command.

1.3.3. Network console

barebox has a UDP-based network console. If enabled in the config, you will see something like this during startup:

registered netconsole as netconsole

By default the network console is disabled during runtime to prevent security risks. It can be enabled using:

netconsole.ip=192.168.23.2
netconsole.active=ioe

This will send UDP packets to a PC with IP address 192.168.23.2 and port 6666.

The netconsole.active parameter consists of the fields “input” (i), “output” (o) and “error” (e); if the fields are set, the respective channel is activated on the network console.

On the PC side, the scripts/netconsole script can be used to remote control barebox:

scripts/netconsole <board IP> 6666

The netconsole can be used just like any other console. Note, however, that the simple console protocol is UDP based, so there is no guarantee about packet loss.

1.3.4. DSA (Distributed Switch Architecture) Support in Barebox

Barebox includes support for DSA (Distributed Switch Architecture), allowing for basic configuration and management of network switches within the bootloader.

DSA enables network devices to use a switch framework where each port of the switch is treated as a separate network interface, while still allowing packet forwarding between ports when enabled.

1.3.4.1. DSA Configuration

DSA switches are managed through device parameters, similar to network interfaces. Each switch is identified as a separate device, typically named switch0 or switch@00 depending on the bus address.

1.3.4.1.1. Global Forwarding Control

A parameter, forwarding, allows configuring whether a switch operates in isolated mode (default) or forwarding mode:

• Isolated Mode (default): Each port is treated as an independent interface, with no forwarding between ports.

• Forwarding Mode: The switch allows forwarding of packets between ports, acting as a traditional non-managed switch.

To check the current DSA switch settings, use:

barebox:/ devinfo switch0
Parameters:
  forwarding: 0 (type: bool)

To enable forwarding mode:

dev.switch0.forwarding=1

To disable forwarding and revert to isolated mode:

dev.switch0.forwarding=0

1.3.4.1.2. Persisting Configuration

To ensure that the forwarding mode setting persists across reboots, it can be stored as a nonvolatile (nv) variable:

nv dev.switch0.forwarding=1

This will configure the switch to always boot in forwarding mode.

1.3.4.2. Integration with Network Interfaces

Each port of the DSA switch is exposed as an independent network interface in Barebox. However, when forwarding is enabled, packets can be forwarded between these interfaces without requiring intervention from the CPU.

To configure network settings for individual ports, use standard network configuration variables (e.g., eth0.ipaddr, eth0.mode, etc.). These settings are applied per port and are independent of the global switch forwarding configuration.