Pfinet is a TCP/IP stack from an old linux version. It works but is not maintained. Recently Recently lwip, which is an userspace tcp/ip library, was ported to the Hurd, which can serve as a direct replacement for pfinet.
To configure Internet connectivity, the pfinet (Protocol Family Internet)
translator must be configured. This is done using the
settrans command, for example like this:
# settrans -fgap /servers/socket/2 /hurd/pfinet ↩
-i /dev/eth0 -a 192.168.0.50 -g 192.168.0.1 -m 255.255.255.0
The argument /server/socket/2 is the node that the translator is to be
attached to. This is followed by the translator program to run and any
arguments to give it.
There, -i, -a, -g and -m are, quite obviously, the (Mach) device to
use, the IP address, the gateway and netmask.
To make DNS lookups work, you'll also have to properly configure the
/etc/resolv.conf file, for example by copying it over from your GNU/Linux
installation.
DHCP.
IPv6.
eth-filter: Firewall.