examples: make nm-dispatcher script usable for networkd-dispatcher

Historically there were plenty of callback based implementations around
ifupdown via /etc/network/if-up and similar. NetworkManager added the
dispatcher [1] feature for such a kind of functionality.

But so far a systemd-networkd (only) systemd had no means to handle those
cases. This is solved by networkd-dispatcher which is currently available
at least in ArchLinux and Ubuntu.
It takes away the responsibility to listen on netlink events in each
application and provides a more classic script-drop-in interface to respond
to networkd events [3].

This commit makes the NM example compatible to be used by NetworkManager
dispatcher as well as by networkd-dispatcher. That way we avoid too much
code duplication and can from now on handle special cases in the
beginning so that the tail can stay commonly used.

After discussion on IRC the current check differs by checking the
argument count (only in NetworkManager), if ever needed we could extend
that to check for known custom environment vars (NetworkManager =>
CONNECTION_UUID; networkd-dispatcher => OperationalState).

[1]: https://developer.gnome.org/NetworkManager/stable/NetworkManager.html
[2]: https://github.com/craftyguy/networkd-dispatcher
[3]: https://github.com/systemd/systemd/blob/master/src/systemd/sd-network.h#L86

Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>

diff --git a/examples/chrony.nm-dispatcher b/examples/chrony.nm-dispatcher
index a609a66f5bc9acbbfe59ee81a449d3c809ef57dc..8bd7df01d4a1ee089c90cbf45f50a410889f69e1 100644 (file)
--- a/examples/chrony.nm-dispatcher
+++ b/examples/chrony.nm-dispatcher
@@ -1,10 +1,14 @@
 #!/bin/sh
-# This is a NetworkManager dispatcher script for chronyd to set its NTP sources
-# online or offline when a network interface is configured or removed
+# This is a NetworkManager dispatcher / networkd-dispatcher script for
+# chronyd to set its NTP sources online or offline when a network interface
+# is configured or removed
 
 export LC_ALL=C
 
-[ "$2" != "up" ] && [ "$2" != "down" ] && exit 0
+# For NetworkManager consider only up/down events
+[ $# -ge 2 ] && [ "$2" != "up" ] && [ "$2" != "down" ] && exit 0
+
+# Note: for networkd-dispatcher routable.d ~= on and off.d ~= off
 
 # Check if there is a default route