Update usage

README.md

@@ -1,13 +1,41 @@
 # Wolz
 
-- Broadcast Wake on Lan (WoL) magic packet to network devices in the local network.
-- WoL only works if the target network interface supports it and is not in low power mode.
-- Check [arch wiki](https://wiki.archlinux.org/title/Wake-on-LAN) on this subject to setup your device to Wakup on LAN.
+- Wake up or shutdown a device on the local network
+    - Broadcast Wake on Lan (WoL) magic packet to wake up.
+        - WoL only works if the target network interface supports it and is not in low power mode.
+        - Check [arch wiki](https://wiki.archlinux.org/title/Wake-on-LAN) on this subject to setup your device to Wakup on LAN.
+    - Run a daemon on the target machine to accept shutdown requests.
+
+## Design goals
+
+- Do not have any dependency on other crates, only on shared libraries shipped with the distro.
+- Do not start any additional process. (No Command::new stuff)
+- Configuration should only have MAC addresses as they are permanent for a device. Do not configure any IP address
 
 ## Usage
 
 Run `wolz` to view the help text.
 
+### Shutdown functionality
+
+Run `wolz` under daemon mode to start listening to tcp traffic on port (check code for port). Make sure firewall doesn't block.
+
+The daemon process can be started as systemd service after network.targets. The user running should have the following permissions, setup in polkit. Create a new rule.
+
+```
+$ # Read the config below and update the subject.user as appropriate
+$ cat /etc/polkit-1/rules.d/50-poweroff-chips.rules 
+polkit.addRule(function(action, subject) {
+    if ((action.id == "org.freedesktop.login1.power-off" ||
+         action.id == "org.freedesktop.login1.power-off-multiple-sessions" ||
+         action.id == "org.freedesktop.login1.reboot" ||
+         action.id == "org.freedesktop.login1.reboot-multiple-sessions") &&
+        subject.user == "chips") {
+        return polkit.Result.YES;
+    }
+});
+```
+
 ## Troubleshooting
 
 This tool broadcasts the magic packet to the broadcast address (and port 9) of all networks the physical interfaces connect to.

src/main.rs

@@ -47,14 +47,19 @@ fn main() -> WResult<()> {
 fn print_usage() -> WResult<()> {
     println!(
         "{}",
-        r#"usage: woly ARG
+        r#"usage: woly COMMAND ARG
 
 Options:
-         ARG   Either the mac address of the device to send the wol magic
-               packet to, or a nickname specified in woly.conf to lookup
-               the mac. See details about config file below.
-               Eg: woly aa:bb:cc:dd:ee:ff
-               Eg: woly potato
+     COMMAND   One of `up`, `down` or `daemon`
+               `up`     - wakes up the device.
+               `down`   - shuts down the device.
+               `daemon` - Runs a daemon. This needs to be running on
+                          the target machine that needs to be shutdown
+         ARG   Either the mac address of the device or a nickname
+               specified in woly.conf to lookup the mac. See details
+               about config file below.
+               Eg: woly up aa:bb:cc:dd:ee:ff
+               Eg: woly down potato
 
 Config file:
     Filename   woly.conf