net-tools is a popular Linux Open-Source package includes the important user-space tools for controlling the network subsystem of the Linux kernel. Which includes arp, rarp, ifconfig, ipmaddr, mii-tool, netstat, rarp, nameif, route, iptunnel and so on.
Refer:
net-tools project links:
net-tools sourceforge.net ↗
net-tools sourceforge.net Project ↗
net-tools Linux Foundation Wiki ↗
net-tools Git source ↗
ifconfig.c ↗
Linux Kernel source:
kernel-source -> net/ipv4 ↗
arp.c ↗