exit: enable forwarding directed broadcasts for WoL

Must be set in IPv4 sysctls for all interfaces and every input
interface from which broadcasts are sent. These are the virtual
MLAG interfaces (bridge-*-v0), which are created dynamically.

We enable directed broadcasts for (only MLAG) interfaces enumerated by
the ifaces_directed_broadcast value in NetBox device local context.

roles/exit/files/sysctl.conf

@@ -0,0 +1,2 @@
+# enable directed broadcasts for WoL, must also be enabled on input interfaces to take effect
+net.ipv4.conf.all.bc_forwarding = 1

roles/exit/tasks/main.yml

@@ -1,3 +1,8 @@
+- name: Set up sysctls
+  copy:
+    dest: /etc/sysctl.d/local-exit.conf
+    src: sysctl.conf
+
 - name: Set up networks
   template:
     dest: /etc/network/interfaces.d/networks.intf