init-scripts/docs/network.md

Static Network Configuration

The default configuration provides multiple services that perform network initialization and static configuration using helper scripts that require programs from the iproute2 package.

Configuration files are typically stored in /etc/netcfg/ (depending on configure options).

Please note that the loopback device is treated specially and not included in any of the network configuration outlined below. The loopback device is brought up and configured by a dedicated service long before the network configuration is done.

Interface Renaming

If the ifrename service is enabled (it is disabled by default), network interfaces are renamed based on a rule set stored in the file ifrename. The file contains comma separated shell globing patterns for the current interface name, MAC address and a prefix for the new interface name.

For each network interface, rules are processed top to bottom. If the first two globing patterns apply, the interface is renamed. Interfaces with the same prefix are sorted by mac address and a running index is appended to the prefix.

If none of the rules apply, the interface name is left unchanged.

The intent is, to provide a way to configure persistent, deterministic names for at least all network interfaces that are permanently installed on a board.

Extension cards or external network adapters should be given a different prefix to avoid changes in the order as they come and go.

Interface Configuration

After interface renaming, for each network interface, the configuration path is scanned for files with the same name as the interface.

Each successfully found configuration file is processed line by line, top to bottom. Each line may contain a keyword, followed by multiple arguments.

The following keywords can be used to add IPv4 or IPv6 network addresses to an interface:

• address
• addr
• ip
• ip6
• ipv6

Those commands are expected to be followed by an IPv4 or IPv6 address and network mask.

Furthermore, the following commands can be used for configuring interface parameters:

• arp {on|off}
• multicast {on|off}
• mtu <value>
• offload [rx {on|off}] [tx {on|off}] [sg {on|off}] [tso {on|off}]
• offload [gso {on|off}] [gro {on|off}] [lro {on|off}] [rxvlan {on|off}]
• offload [txvlan {on|off}] [ntuple {on|off}] [rxhash {on|off}]
• offload [ufo {on|off}]

Route Configuration

After interface configuration is done, routes and rules are restored from a file named routes in the same configuration path.

The file may contain lines starting with route or rule. Everything that follows is passed on to ip route add or ip rule add respectively.

Net Filter Tables

An additional service is provided that restores the nft rule set from /etc/nftables.rules.

DHCP based network configuration

If the configure option --enable-dhcpclient is set, two services are added. The service dhpcdmaster launches a global dhcpcd instance.

For each port that should be configured via DHCP, the service dhcpcd needs to be enabled manually with the port name as argument. The service the runs after the master service and sends a signal to the master to operate on that port.