Autodetect network interfaces during boot and configure them for DHCP
The rationale for this is that we are likely to require multiple network interfaces for use cases such as baremetal and there is no way to know ahead of time which one is which, so we will simply run a DHCP client on all interfaces with real MAC addresses (except lo) that are visible on the first boot.
On non-Gentoo based distributions the script /usr/local/sbin/dhcp-all-interfaces.sh will be called early in each boot and will scan available network interfaces and ensure they are configured properly before networking services are started.
On Gentoo based distributions we will install the dhcpcd package and ensure the service starts at boot. This service automatically sets up all interfaces found via dhcp and/or dhcpv6 (or SLAAC).
Amount of time in seconds that the systemd service(or dhclient) will wait to get an address. Should be increased in networks such as Infiniband.
When NetworkManager is detected, and this is set to true the dhcp-all-interfaces service will not be installed. Only the NetworkManager configuration will be added. NetworkManager is quite capable to do automatic interface configuration. NetworkManager will by default try to auto-configure any interface with no configuration, it will use DHCP for IPv4 and Router Advertisements to decide how to initialize IPv6.