Open Source Router Firmware

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Asus RT-N56U[edit]

ASUS RT-N56U/N65U/N14U/N11P/AC51U custom firmware

RT-N56U Wiki: Common Tips

Interrogating Clients[edit]

There are several options available to list the clients that are currently connected to a router running Linux-based firmware.

At the most basic level is ARP, the Address Resoluton Protocol. List the devices in the ARP cache (name, IP address, and MAC address) with arp. The cache is usually refreshed every minute or so, as defined in a file called gc_stale_time; search for this file with find / -iname gc_stale_time.

For more detailed status information, try ip neighbor from the iproute2 networking toolset. In addition to listing the IP and MAC addresses, each device's current status (REACHABLE, STALE, DELAY, &etc) is included. When a device is disconnected, you can watch it traverse the statuses until it's dropped from the ARP cache.

If your router uses dnsmasq for DHCP (very many do), you can view the current list of static and dynamic leases in the file dnsmasq.leases; search for this file with find / -iname dnsmasq.leases. The list of leases is updated rapidly after device connection or disconnection. To see if the device 'bcurtis-motox' is currently connected, you could use something like cat /tmp/dnsmasq.leases | grep bcurtis-motox

Waking Up Clients[edit]

Many devices support Wake-On-LAN (WOL), and can be woken up with a command sent over the network. In the RT-N56U firmware, this is accomplished with the ether-wake utility. To wake up the device with MAC address F4:6D:04:1F:02:1B, use ether-wake -b -i br0 F4:6D:04:1F:02:1B

This can be especially fun when combined with scheduled tasks in crontab. This code wakes up the device with MAC address F4:6D:04:1F:02:1B when the device 'bcurtis-motox' comes online:

motox=$(arp | grep bcurtis-motox)
if [ -n "$motox" ]; then
    ether-wake -b -i br0 F4:6D:04:1F:02:1B

Building a Toolchain for Cross-Compilation[edit]

Entware is an Open-WRT tool, so it was never intended to offer native compilation:

Is it possible to add a buildroot/gcc package to entware (also automake, autoconf, etc)? Because with optware you have that and i compile small things on the router itself (is faster than crosscompiling and trasnferring everytime)!

In fact, Entware is OpenWRT, so no native compilation is provided. Not for now, not in future. A modern gcc eats too much memory for running on embedded devices. We may port it without any optimisations (-O2, -O3, -Os), but it will be useless.

Instead, you can set up a toolchain on another machine to cross-compile software for the router: